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Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
Pain Perception at Different Stages of Orthodontic Treatment
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Pain Perception at Different Stages of Orthodontic Treatment

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  • 1. KUOPION YLIOPISTON JULKAISUJA D. LÄÄKETIEDE 452 KUOPIO UNIVERSITY PUBLICATIONS D. MEDICAL SCIENCES 452 FARSHAD DALILI Pain Perception at Different Stages of Orthodontic Treatment Doctoral dissertationTo be presented by permission of the Faculty of Medicine of the University of Kuopio for public examination in Auditorium L22, Snellmania building, University of Kuopio, on Saturday 19 th September 2009, at 12 noon Faculty of Medicine Institute of Biomedicine, Department of Physiology University of Kuopio JOKA KUOPIO 2009
  • 2. Distributor : Kuopio University Library P.O. Box 1627 FI-70211 KUOPIO FINLAND Tel. +358 40 355 3430 Fax +358 17 163 410 www.uku.fi/kirjasto/julkaisutoiminta/julkmyyn.shtmlSeries Editors: Professor Esko Alhava, M.D., Ph.D. Institute of Clinical Medicine, Department of Surgery Professor Raimo Sulkava, M.D., Ph.D. School of Public Health and Clinical Nutrition Professor Markku Tammi, M.D., Ph.D. Institute of Biomedicine, Department of AnatomyAuthor´s address: Siilinjärvi and Maaninka, Health Centre Department of Dentistry Kasurilantie 3 FI-71850 SIILINJÄRVI FINLANDSupervisors: Professor Matti Närhi, DDS., Ph.D. Institute of Biomedicine, Physiology Section University of Kuopio Professor T. Maija Laine-Alava, DDS., M.Sc., Ph.D. Secretary General, Finnish Dental Society HelsinkiReviewers: Professor William Proffit, DDS., M.Sc., Ph.D. School of Dentistry, University of North Carolina, Chapel Hill, North Carolina, U.S.A. Professor Mauno Könönen, DDS., M.Sc., Ph.D. School of Dentistry, Department of Physiology and Prosthetics University of HelsinkiOpponent: Professor Timo Peltomäki, DDS., M.Sc., Ph.D. School of Dentistry, Department of Orthodontics and Pediatric Dentistry University of Zurich, SwitzerlandISBN 978-951-27-1172-7ISBN 978-951-27-1209-0 (PDF)ISSN 1235-0303KopijyväKuopio 2009Finland
  • 3. Dalili, Farshad. Pain perception at different stages of orthodontic treatment. Kuopio UniversityPublications D. Medical Sciences 452. 2009. 99 p.ISBN 978-951-27-1172-7ISBN 978-951-27-1209-0 (PDF)ISSN 1235-0303ABSTRACTThe purpose of the present study was to assess pain experience as reported by the patients during different stages oforthodontic treatment. Further, the aim was to examine the extent of which the sensitivity of the dental pulp might beaffected by orthodontic treatment and if such changes could explain the mechanisms and origins of the pain symptoms.The study group consisted of 64 voluntary patients, 46 females and 18 males, with a mean age of 26.4 (SD 11.1) years.Patients were requested to fill out a structured questionnaire for three consecutive days after the insertion of orthodonticseparators, after the initial archwire placement, and after the archwire activation. The intensity (mild, moderate, severe),quality (sore, shooting, dull, ache) and the duration (short, long) of the pain symptoms in connection with seven itemswere evaluated, namely: eating sweets, having hot or cold food/drink, tooth brushing, mastication of food, fittinganterior and fitting posterior teeth together. Clinical study regarding tooth sensitivity included measurements of theelectrical thresholds with a constant current stimulator and cold sensitivity with an electrothermal device at 0ºC and15ºC. A 100 mm Visual Analogue Scale (VAS) was used to assess the intensity of the cold responses to cold. Toothmovement/s were measured using the irregularity index (Little 1975) for the anterior teeth (canine to canine), inaddition to tooth movements (mm) into the extraction spaces after three months of orthodontic force application. Proportion of the patients who had experienced pain was 70% after insertion of the separators, 96% after placementof the initial archwire and 69% after archwire activation, with the highest proportions during the first day after eachprocedure. The intensity of pain was mostly reported to be mild 62.5%, followed by moderate 28.5% and severe 9%,respectively. Regarding the quality the sensory experience was described as sore, shooting, dull and ache in 63.5%,14.3%, 14.3% and 7.9% of the reports, respectively. Duration of pain was mostly short, in 85% of the sample.Regarding the listed items, mastication of food, fitting anterior and posterior teeth together, tooth brushing, cold and hotfood/drink and sweets, in descending order, gave the most frequent pain reports. Dental electrical thresholds weregenerally unchanged before, during and after different orthodontic procedures. Proportion of teeth responding to thecold sensitivity tests as well as the intensity of the pain responses were higher at 0ºC than 15ºC, and were associatedwith the pain experienced at different stages of orthodontic treatment. In general the differences in the prevalence of thepain and the tooth movement with regards to anterior crowding, between the two different fixed orthodontic applianceswere small. However, there was a difference in tooth movements into extraction spaces between the two fixedorthodontic appliances. It is concluded that 1) pain symptoms are common and the prevalence of such experiences varies at different stagesof orthodontic treatment, insertion of the initial archwire being the most painful stage, 2) the intensity of theexperienced pain was mostly mild followed by moderate pain reports and less frequently severe pain, 3) the inducedpain is mostly due to periodontal nociceptor responses which is reflected by the frequent pain reports during masticationand fitting teeth together, 4) increased dental sensitivity to cold due to sensitization of the pulpal nerves suggests alsopulpal involvement which seems to partly explain the origin of the pain symptoms in connection with orthodontictreatment, and finally 5) slight differences in the applied forces, due to the use of different initial archwires, provokedno apparent increase either in the pain experienced by the patients or in the dental sensitivity.National Library of Medicine Classification: WU 400, WL 704Medical Subject Headings: Dentistry; Orthodontics; Tooth Movement; Pain; Facial Pain;Toothache; Analgesia; Pain Measurement; Questionnaires
  • 4. ACKNOWLEDGMENTSI would like to express my deepest gratitude to the supervisors of this study, Professor Matti NärhiDDS., Ph.D., for his discerning professional advice in many theoretical and practical matters. Healways has had time for my questions and guided this work with warmth and supportingencouragement.My sincere thanks to Professor T. Maija. Laine-Alava DDS., MSc., Ph.D., for the supportingoptimism and professional guidance until the end. Helping me realize the importance of paincontrol in orthodontics.I wish to extend appreciations to Professor William Proffit DDS., MSc., Ph.D., of the University ofNorth Carolina, USA, the official reviewer of this study who blessed me with his constructivecomments and criticism of the manuscript.My thanks to Professor Mauno Könönen DDS., Ph.D., of the University of Helsinki, the officialreviewer for his constructive comments.This study was carried out at the Departments of Orthodontics and Physiology of University ofKuopio and at the Department of Oral Development and Orthodontics, Institute of Dentistry,University of Turku, and finalized at the Institute of Biomedicine, Physiology Section, Universityof Kuopio, Finland.I am grateful to Professor Juha Varrela DDS., MSc., Ph.D., Head of the Department of OralDevelopment and Orthodontics of University of Turku, Finland, for his support.To the personnel of the Orthodontic Department and all the patients and their parents whovolunteered to participate in this study I owe my warmest thanks.The orthodontic materials of this work have been supported partly by Ormco and GACinternational, which I acknowledge with gratitude.Many thanks to Dr. Anthony Viazis DDS., MSc., of Dallas, Texas, USA, for introduction of hisapproach to fixed orthodontic therapy.My thanks to Seppo Lammi, Head of the Department of Computer Sciences of the University ofKuopio for his guidance and advice with the statistical analyses.I owe my special thanks to Riitta Myllykangas for all the efforts she has put in to this study.I wish to thank my teachers and colleagues at the University of Kuopio for their support. Dr. VeijoMiettinen former head of the Dental Clinic, acting Professor Dr. Pauli kilpeläinen Ph.D., Dr.Armando Gale Associate professor, Dr. Riitta Pahkala Ph.D., Associate professor.Many thanks to my dear family for their loving support during this work. To my lovely sons Nikuand Sam who have provided me with the encouragement for all strivings in my life. I owe mywarmest thanks to my dear wife Dr. Najin Atashkari DDS., MSc., who has been strongest supporterof this study by taking care of every other detail in our lives to provide me the precious time Ineeded to finalize this research.September 2009,Farshad Dalili
  • 5. CONTENTS ACKNOWLEDGMENTS1. INTRODUCTION2. REVIEW OF LITERATURE 2.1. Mechanism of the pain symptoms related to orthodontic treatment 2.2. Optimal forces for tooth movements 2.3. Dental pulp reactions to orthodontic forces 2.4. Variation of the perceived orthodontic pain with age and gender 2.5. Measurement of tooth sensitivity 2.6. Management of orthodontic pain3. AIMS OF THE PRESENT STUDY4. SUBJECTS AND METHODS 4.1. Subjects 4.2. Orthodontic mechanotherapies used for the study subjects 4.3. The questionnaire 4.4. Clinical examination 4.4.1. Dental electrical threshold measurement 4.4.2. Testing thermal sensitivity of the teeth 4.5. Measurement of tooth movement from hard stone casts 4.6. Study protocol 4.7. Statistical methods5. RESULTS 5.1. Subjective pain experience during orthodontic treatment as reported in the questionnaires 5.1.1. Prevalence of the pain 5.1.2. The intensity, quality and duration of the pain 5.1.3. Pain experienced during the three days subsequent to each orthodontic procedures 5.1.4. Pain experienced in relation to different stimuli of the questionnaire 5.1.5. The relationship between subjective pain reports and the analgesic consumption 5.1.6. Relationship between subjective pain reports and age, gender, extraction(s) and the extent of treatment 5.2. Clinical study 5.2.1. Responses to cold stimulation 5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0 and 15ºC
  • 6. 5.3. Comparison of two different orthodontic mechanotherapies 5.3.1. Dental cold sensitivity and electrical thresholds in two different orthodontic mechanotherapies 5.3.2. Tooth movements in two different orthodontic mechanotherapies6. DISCUSSION 6.1. Study subjects 6.2. Measurement of the experienced pain 6.2.1. The questionnaire 6.2.2. Subjective pain symptoms related to different orthodontic procedures 6.2.3. Intensity, quality and duration of the pain symptoms 6.2.4. Analgesic consumption 6.2.5. Dental pain sites 6.2.6. The relationships between the pain symptoms during initial tooth movement and age, gender, and treatment approach 6.3. Clinical study 6.3.1. Electrical tooth stimulation 6.3.2. Cold sensitivity tests 6.3.3. Comparison of different fixed oerthdontic appliances7. SUMMARY AND CONCLUSIONSREFERENCESAPPENDIX
  • 7. 1. INTRODUCTIONPain is perhaps even older than mankind. There is a reason to believe that it is inherent in any lifelinked with consciousness. Evidence indicates that man has suffered this affliction since hisbeginning, for one finds testimony to the existence of pain in the chronicles of all races (Fulöp-Miller 1938). The international Association of the Study of Pain has defined pain as: “anunpleasant sensory and emotional experience associated with actual or potential tissue damage ordescribed in terms of such damage” (Wall and Melzack 1994).Accordingly, pain is a complex experience that includes sensations evoked by noxious stimuli andthe reactions to such stimuli. The subjective reactions vary among individuals and can depend on aperson’s cultural background, past experiences, and other forms of psychologic input that givemeaning to a situation in which pain occurs (Burstone 1985).Pain and pain control are important to dental profession, since general perception of public is thatdental treatment and pain are inseparable and go hand in hand. Orthodontic tooth movementrequires application of force to the tooth, which generally causes pain (Walker et al. 1987) althoughnot much knowledge exists on the intensity and quality of such pain symptoms. Because of itsobvious importance in orthodontics, one would assume a large volume of research on the treatmentof the related pain, which unfortunately is not the case. The intensity of the pain symptoms has beenstudied to some extent (Tayer and Burek 1981, Ngan et al. 1989 and 1994, Brown and Moerenhout1991, Jones and Chan 1992, Scheurer et al. 1996). However, there is little knowledge on the qualityand duration of such symptoms and their significance regarding the treatment.The discomfort related to tooth movement is a subject little discussed by clinicians and given littleattention in orthodontics. There are reports that one of the discouraging factors for seekingorthodontic treatment is the individual’s fear for the related pain and discomfort (Oliver and Knap-man 1985). In most cases, the quality and extent of the information about orthodontic treatment andthe related discomfort seems to be satisfactory, but still many people report not having been well-informed prior to the procedures (Oliver and Knapman 1985).The control of pain in orthodontic therapy should include adjusting the forces to a level below thepain thresholds. Unfortunately, such low forces would have very little if any effect on the toothmovement. To alleviate the pain and discomfort clinicians have tried different approaches: aconventional pharmacological analgesia (Simmons and Brandt 1992), physiologically by having 9
  • 8. patients to chew on something fairly hard for example a plastic wafer (Furstman and Bernick 1972),analgesic chewing gums (White 1984), transcutaneous electrical nerve stimulation (TENS, Rothand Thrash 1986), low level laser therapy (Lim et al. 1995), and magnetic force fields (Blechman1998).The initial pain/discomfort experienced during orthodontic treatment for the first couple of daysafter force application is a generally accepted observation. Many factors have been thought to affectthe extent of the symptoms, namely the intensity and duration of forces applied, age, gender, thedegree of crowding of the arch/es, patient’s psychological background and past experiences. Thereis a traditional belief of the existence of a causal relationship between the amount of the forceapplied to the tooth and the severity of the pain experience.It seems to be a general assumption that the only sources for the pain in connection with orthodontictreatment are the periodontal tissues or, more generally, tissues outside the tooth pulp. However,many studies indicate that the pulp circulation and tissue metabolism and even vitality may beaffected or compromised by the applied forces (Butcher and Taylor 1952, Stenvik and Mjör 1970,Biesterfield et al. 1979, Hamersky et al. 1980, Labat et al. 1980, Unterselher et al. 1987). Dentalelectrical thresholds as an indicator of tooth vitality have been studied, however, not as a measure ofpossible sensitivity changes in the pulpal nerves. The possible changes in the pulp nerve sensitivityand their connection to orthodontic pain symptoms have evoked little attention.Technological advances have long influenced orthodontic mechanotherapy approaches.Introduction of superelastic, heat-activated archwires to orthodontics, claims to enable thepractitioner to reduce the treatment time by combining different stages of orthodontic treatmentdone separately earlier, namely alignment, leveling and tooth movement (Viazis 1993, 1995, 1998).The extent of which such approach might affect the type and amount of the tooth movement, theperception of pain and discomfort experienced, and also the tooth responses, is not known. Theorthodontic profession needs critical clinical data on the relative efficiencies of differentbiomechanical strategies of tooth movement. From a cost-benefit point of view, orthodontictreatment should be performed as quickly as possible without jeopardizing the affected tissues. Amajor question is which approach provides minimum discomfort, the most rapid orthodontic toothmovement with the least damage to the teeth and the supporting structures. 10
  • 9. 2. REVIEW OF LITERATURE2.1. Mechanism of the pain symptoms related to orthodontic treatment.Nociceptive afferents transmit their messages to the central nervous system at different rates,depending on the size and type of the axons. Both myelinated (A-type) and unmyelinated (C-type)nerve fibers enter the pulp and periodontium (Reader and Foreman 1981, Holland and Robinson1983, Byers 1984). A δ-fibers have diameters that vary between 2-4 and 20 microns with theconduction velocity of upto 30 meters per second. A -fibers are present in somatic and visceralnerves. They carry mechnoreceptive signals, pressure and proprioceptive impulses at the speed thatmay exceed 100 meter per second. The unmyelinated C-fibers have a smaller diameter, up to 2microns. Majority of them carry nociceptive signals but at a lower speed, approximately 0.5-2.5meters per second.Functional differences between, as well as their differences in the character of the tooth painassociated with pulpal A- and C-fibers have been reported (Närhi 1985a, b, Jyväsjärvi and Kniffki1987, Närhi et al. 1992a, b). Hydrodynamic mechanism, which is believed to activate A-fibers, ismost probably responsible for dentin sensitivity. C-fibers are activated by a direct effect of thermal,mechanical and chemical irritants, for example, by bradykinin and histamine (Närhi 1985, Närhi etal.1992). Heat stimulation induces an immediate sharp pain, which is due to A δ-fiber activation,and a delayed dull pain indicative of C-fiber activity (Närhi et al. 1982a, 1984, Närhi 1985a,Jyväsjärvi and Kniffki 1987). A δ-fibers are thought to be involved in the mediation of pain in theinitial phases of pulpal inflammation (sharp pain), the dull pain induced during the later phases isprobably due to C-fiber activation (Mumford 1982, Närhi 1985, Olgart 1985).Release of neuropeptides has been suggested to be related to the activation of C-fibers and somesmall diameter A δ-fibers (Byers et al. 1992b, Närhi et al. 1994, Byers and Närhi 1999).Prostaglandins have been shown to increase intradental nociceptor sensitivity to thermal stimulationand cause hyperalgesia (Ahlberg 1978) as do some other inflammatory mediators activated orreleased in connection with tissue injury (Närhi et al. 1992, 1994). It is probable that inflammatoryreactions and nerve sensitization also take place in the periodontal tissues (Yamaguchi and Kasai2005), although such responses in the PDL have been much less studied than the pulp nervereactions. Thus, tissue injury and consequent inflammation of gingival and periodontal tissuesduring orthodontic treatment could lower pain threshold by inducing nociceptor sensitization. These 11
  • 10. tissues may then become responsive to stimuli that would not ordinarily evoke any pain reaction(Ngan 1994).During orthodontic tooth movement the collagen fibers of periodontal ligament are disrupted, withsome part of the ligament undergoing compression and others tension. Initial healing of wounds inthe periodontal ligament begins with blood clot and granulation tissue formation subsequent tonecrosis regardless of the type of the periodontal challenge (Sismanidou et al. 1996). Organizationof granulation tissue follows, during which vascular and nervous components (Parlange and Sims1993) as well as new periodontal connective tissue (Melcher 1970, 1976, Line et al. 1974, Catonand Nyman 1980, Harison and Jurronsky 1991, Wikesjo et al. 1992) enter the area.It has been suggested that the periodontal ligament nociceptive nerve fibers perform two mainfunctions: transmission of pain impulses centrally (Mengel, Jyväsjärvi and Kniffki 1992, 1993) andrelease of neuropeptides peripherally (Davidovitch 1991). Närhi (1978) recording from the singlepulpal nerve fibers, found that an increase in the tissue pressure increases sensory nerve activity.However, our knowledge regarding the function of the periodontal nociceptors is limited. It hasbeen shown, however, that they respond to strong forces applied to the tooth (Mengel, Jyväsjärviand Kniffki 1992, 1993). Khayat et al. (1988) suggested that after pulp tissue injury sprouting of thenerve fibers in the pulp and apical periodontium might potentiate dental pain sensitivity bymultiplying the receptor sites.The increase in the expression of Calcitonin Gene-Related Peptide (CGRP) and Substance P (SP)during the first two days after application of an orthodontic force in the rat (Kvinnsland et al. 1990,Norevall et al. 1995) is interesting, considering the findings in clinical human studies that show painsymptoms reaching the peak approximately one to two days after force application (Furstman andBernick 1972, Wilson et al. 1989, Ngan et al. 1989, 1994, Jones and Chan 1992).Pain connected to orthodontic tooth movement most probably originates from the periodontaltissues due to mechanical injury and consequent inflammatory reaction. However, also intradentalnociceptive nerves may be involved because periodontal inflammatory reactions may spread to thepulp due to formation and diffusion of various inflammatory mediators, and neurogenicinflammation mediated by branching axons, which are known to innervate both the pulp andperiodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b, Yamaguchi and Kasai 2005).Moreover, as already mentioned, nerve sprouting also takes place within the pulp in response toorthodontic forces, which may affect the functional properties of the intradental nerves. Also, 12
  • 11. possible impairment of the pulpal blood flow due to vessel compression may play a role.As already mentioned due to the neurogenic effects transmitted by branching axons innervatingboth the pulp and PDL, the effects of periodontal tissue injury may also be reflected in the pulp. Towhat extent pulpal inflammatory reactions and consequent increase in intradental nerve sensitivityplay a role in the pain responses to orthodontic tooth movement is not known.2.2. Optimal forces for tooth movementMany investigators have reported a relationship between the magnitude of applied force anddifferent types of tooth movement (Smith and Storey 1952, Reitan 1957, 1960, Burnstone andgroves 1961, Andreasen and Johnson 1967, Hixon et al. 1969, 1970, Mitchell et al. 1973,Andreasen and Zwanziger 1980, Maltha et al. 1993, Owman-Moll et al. 1995, 1996, Bergius et al.2002).The term optimum orthodontic force is usually regarded as meaning the force that moves teeth mostrapidly, with the least discomfort to the patient and least damage to the teeth and their investingtissues. In 1932 Schwarz stated that biologically the most favorable treatment is that which workswith forces not greater than the pressure in the blood capillaries. Oppenheim (1944) and Reitan(1959) have also reported the optimal force levels based on capillary blood pressure in theperiodontal membrane. Schwartz (1932) in his experience, recommended light, continuous forcesbecause he was of the opinion that this prevents the formation of resorption-resistant osteoid boneand certain reparative processes on the side toward which tooth moves. Burstone (1985)characterized optimal force by maximal cellular response from the tooth supporting tissues,including apposition and resorption of alveolar bone, at the same time as the maintenance of thevitality of these tissues is secured. Thus, the amount of tooth movement is not the only indicator ofoptimal force.Light differential forces for tooth movement have been recommended, the assumption being that adifferential movement of the teeth can generally be achieved. Moreover, it is generally thought thatlight forces are somewhat more efficient and more biologic and, hence, less painful (Storey andSmith 1952, Reitan 1956). Reitan (1957, 1960, 1964, 1985) has always been a spokesman for lightforces, especially at the initial stages of tooth movement, to minimize adverse tissue reaction.However, Hixon et al. (1969) found such a wide variation in response of individuals´ teeth to forcesapplied that they suggested ideal light differential forces to be a myth. With respect to canine 13
  • 12. retraction they found that higher forces were generally more efficient. Boester and Johnston (1974)suggested that out of the three most common arguments favoring light forces, namely efficiency,anchorage preservation and comfort, none could be substantiated in the exact sense of their originalproposal. Gianelly and Goldman (1971) questioned that larger forces cause greater periodontalcompression and result in greater pain. They also questioned the validity of using the pain responseas a guide to the amount of hyalinization of the periodontal ligament.Yamaguchi and Nanda (1991, 1992) have shown that the same degree of forces results in varyingchanges in blood flow and indicated that the change may be subject to deformation of the tissue butnot the degree of force. They concluded that tooth displacement has a closer relationship to thedecreased blood flow than to the degree of force.Jones and Richmond (1985) have reported that the degree of crowding in the arches reflect theoverall forces being applied to the teeth in the arches examined, and demonstrated no correlationbetween the magnitude of the force and the discomfort experienced. Owman-Moll et al. (1995) in aclinical study showed that buccal tipping of maxillary first premolars was less efficiently performedwith an interrupted force than with a continuous one, and found no difference in the number orseverity of areas of root resorption between the two force systems. In an interrupted force systemwith rest periods one would, however, assume less tissue strain and possibly more tooth movementwith less root resorption. Owman-Moll et al. (1996), and Bergius et al. (2008), suggested thatindividual responses might have more impact than the increase in the amount of force or length ofexperimental period on both the tooth movement achieved and occurrence of root resorption.Generally, the use of light continuous force is thought to be the key factor for orthodontic toothmovement. However, the connection between the different recommended ranges of such lightforces and the pain experience is not clear, and the picture seems to become more complex whenthe type and amount of the tooth movement is considered.2.3. Dental pulp reactions to orthodontic forcesThe blood flowing through the tooth is confronted with a unique environment. The dental pulp isincased within a rigid, non-compliant chamber and its survival is dependent on the blood circulationand vessels that access the interior of the tooth through the apical foramen or multiple foramina(Barwick and Ramsay 1996).Understanding the effect of orthodontic force on the pulp is of particular importance, because it 14
  • 13. interferes with pulpal circulation and, thus, the metabolic activity and the respiration rate of the pulptissue (Hamerski et al. 1980, Unterseher et al. 1987). The effects can be reflected as disruption ofthe odontoblast layer (Stenvik and Mjör 1970, Anstendig and Kronman 1974), pulpal obliterationby secondary dentin formation (Marshall 1933, Cywk et al. 1984), root resorption (Spurrier et al.1990, King and Fischlschweiger 1982, Reitan 1964, Vardimon et al. 1991), and even pulpalnecrosis (Butcher and Taylor 1952, Cwyk et al. 1984, Årtun and Urbye 1988), which have all beenassociated with orthodontic treatment. Additionally, the indirect effect of orthodontic forces throughneurogenic interactions may play an important role (Yamaguchi and Kasai 2005).Reversible pulpal injury is a common response to orthodontic treatment (Stenvik and Mjör 1970,Hamersky et al. 1980, Labat et al. 1980, Unterseher et al. 1987). Ikeda et al. (1998) monitoringdental pain thresholds in response to electrical stimulation, demonstrated that light prematurecontacts resulting in abnormal loading of teeth were capable of increasing tooth sensitivity, and thatafter elimination of such interferences, tooth response returned to the base line and clinicalsymptoms disappeared. In animal studies such an injury has been induced, and the severity of thechanges depends on the intensity and duration of the irritation and the resistance of the pulp(Biesterfield, Taintor and Marsh 1979). Butcher and Taylor (1952) reported that experimentalretraction of the lower incisors with 250 gram of force for 3 to 20 days in rhesus monkey producedearly pulpal changes ranging from partial blood flow stasis to necrosis.Intrusive forces have also been considered to have deleterious effects on teeth. Stanley et al. (1978)suggested that a too powerful depressive force may shut off the arterial supply and thus producedevitalization of the pulp. Stenvik and Mjör (1970) reported that with intrusive force on humanpremolars for 4 to 35 days, the main pulpal changes were circulatory disturbances. Further, theeffects of traumatic occlusion and excessive stress of orthodontic forces have been reported to causeextravasations of blood and necrosis of the pulp tissue in human teeth (Seltzer and Bender 1975).Experimental data using respiratory activity (oxidation of organic fuels by molecular oxygen) as anindicator of pulpal injury, have indicated that a 72-hour orthodontic force can cause a 27%reduction of pulp metabolism in human premolars. The respiratory rates remained depressed for atleast one week after the force was discontinued. The metabolic effects were significantly smaller inyounger subjects with more patent root apices than in older people (Hamersky et al. 1980). Onefactor contributing to this apparent decrease in respiration rate could be a strangulation of the bloodvessels and stasis of blood flow to the pulp (Marshall 1933, Orban 1936, Oppenheim 1937,Stuteville 1938, Butcher and Taylor 1951, 1952, Langeland 1957, Anstending and Kronman 1974, 15
  • 14. Guevara et al. 1977). Another interesting finding by Hamerski et al. (1980) was that as the age ofthe subjects increased, the relative amount of depression in the pulpal respiratory rate alsoincreased. These results seem to indicate a relationship between the biologic effect of orthodonticforce and the maturity of the tooth. Accordingly, large apical foramina result in a reduction ofdetrimental effects from orthodontic force.Regulations of the blood flow by sensory nerve fibers, and the related neurogenic inflammatoryreactions have been described in the dental pulp (Gazelius et al. 1987, Olgart 1985, 1990).Neurogenic inflammation effects include the release of vasoactive peptides from the nerve endingsand consequent vasodilation, increased vascular permeability and hyperalgesia. Furthermore, it hasbeen shown that sensory nerve fibers sprout in the inflamed pulp tissue, which may affect itssensitivity (Kimberly and Byers 1988, Taylor et al.1988, Byers et al. 1990b, Michelotti et al. 1999,Yamaguchi and Kasai 2005).2.4. Variation of the perceived pain during orthodontic treatment with age andgenderRelation of age and the perceived pain during orthodontic therapy is not clear, partly because acritical comparison of the various studies is impossible due to differences in experimental designsand methods.Ngan (1989) found significant interaction between the age and duration of force implemented.Patients 16 years of age and younger experienced more discomfort at 4 hours, whereas patientsolder than 16 years of age experienced more discomfort at 24 hours and at the 7th day. Brown andMoerenhout (1991), however, reported that adolescents of 14-17 years of age were more vulnerableto the undesirable psychological effects of treatment and had higher levels of pain than younger andolder patients. Scheurer et al. (1996) also reported that 13-16 years old patients had the highestprevalence of pain. Jones and Richmond (1984) have shown that adults experienced more pain thanadolescents, however, pain experiences do not appear to differ between the genders. Differencesbetween study designs and methodologies may partly explain these different conclusions. Ngan etal. (1989) reported no difference in the perception of pain from orthodontic appliances betweenmales and females. According to Scheurer et al. (1996), however, girls reported a higher impact ondaily life, and significantly greater pain intensity and analgesic consumption than boys in responseto fixed appliances. The changes with age on the perceived pain may relate to the differences in thetissue compliance and tissue repair. However, there is a wide range of individual variations in the 16
  • 15. pain experienced during orthodontic treatment, which is affected, by patients past experiences,cultural background and other forms of psychological input (Burstone 1985).2.5. Measurement of tooth sensitivityFor the measurement of tooth sensitivity it is necessary that the stimulus intensity needed to evoke asensory response can be determined accurately and reliably. Different stimuli have been used forthe purpose. These include; mechanical, thermal, osmotic, dehydrating and electrical stimulation.The sensitivity can be different depending on the type of stimuli used (Lilja 1980, Närhi 1985a,Orchardson and Collins 1987b).The measurement of tooth sensitivity during orthodontic treatment is technically complicated. Onone hand, bonding materials, brackets and archwires limit the accessibility to the tooth surface forstimulation and, on the other hand, open dentinal tubules which may be the basis for pain inductionwith some stimuli may not be found as often in orthodontic patients as in patients with, for example,dentin hypersensitivity.A preferred method of stimulating dental pulp for induction of pain is cold stimulation. It has beenfound to be the most potent (Flynn et al. 1985, Orchardson and Collins 1987b) and also bettertolerated by dental pulp than for example hot stimuli (Pashley 1990). Fulling and Andreasen (1976)reported consistent responses from the teeth, which had stainless steel crown using cold stimulationwith carbon dioxide snow. Electrical stimulation of the teeth was reliable only when thestimulator’s electrode was directly in contact with the enamel, thus, controlling the electricalcurrent leakage.The sensitivity of electric pulp testers for detection of different stages of pulpal inflammation hasbeen questioned (Seltzer et al. 1963, Mumford 1982). Nevertheless, higher accuracy in themeasurement of the applied stimulus by electrical rather than natural stimuli has been noted(Mumford 1982). According to Närhi (1985) since electrical stimulation affects any excitable cellmembrane, it could as well activate intradental axons as peripheral receptors, and thus would not bea valid measure of the pulpal nociceptor sensitivity.Markus (1946) reported that teeth became more responsive to electric pulp testing immediatelyfollowing orthodontic activation while Burnside et al. (1974) found that in general the experimental 17
  • 16. teeth showed higher pain threshold values to electrical stimulation than did the controls indicatingreduced sensitivity. It must be mentioned that in the study of Burnside et al. (1974) the comparisonwas made between the orthodontic patients who had fixed orthodontic appliances for a minimum offour months prior to the test, and the control group had no appliances. Longitudinal studies wouldbe needed to find out the effects of orthodontic tooth movement on the dental pulp sensitivity.McGill Pain Questionnaire (MPQ) measures both the intensity and quality of pain. This verbalrating scale has been used previously for evaluation of pain symptoms in orthodontics, and shownto have high reliability (Brown and Moerenhout 1991). However, vocabulary limitations (Gracely etal.1978) and insufficiency of pain-word questionnaires have been noted (Curro 1990). The VisualAnalogue Scale (VAS) is a direct pain intensity scaling method in which the subjects evaluate thelevel of pain by making a mark on a continuous line. One end of the line means “no pain” and theother end “intolerable pain” (Huskisson 1983). The advantages of using the VAS overobservational, self-report, behavioral, physiological or verbal rating scales, are the highersensitivity, reproducibility and reliability of the direct scaling techniques (Melzack, Torgerson1971, Uskisson 1974, Scott and Huskisson 1979, Huskisson 1983, Seymour et al. 1985, McGrath1986, Duncan et al. 1989). It also allows the use of parametric statistical tests (Bhat 1986). On theother hand, the limitation of VAS is that the recorded values are mostly related to the intensitycomponent of pain.2.6. Management of orthodontic painPain caused by orthodontic treatment can be a major negative component of the entire therapy.Theoretically, the ideal way to control pain during orthodontic treatment would simply be to keepthe applied force levels to a minimum, below the pain threshold. This approach, however, iscontradictory for the purpose if the force levels should be kept too low to result in any toothmovement (Simmons and Brandt 1992).Conventional analgesics have been used to alleviate orthodontic pain. According to Simmons andBrandt (1992) these drugs should be taken prior to the installation of an active orthodonticappliance and for a minimum of 24 hours following the procedure. However, Ngan et al. (1994)reported that single dose given at the moment of orthodontic appliance insertion was sufficient forprevention of pain symptoms. 18
  • 17. In addition to the conventional analgesics more physiological approaches for the treatment orprevention of pain have been applied. Chewing something fairly hard -a plastic wafer, for example-within the first two hours after arch wire adjustment may act to reduce the ischemia andinflammation in the periodontal ligament (Furstman and Bernick 1972). Stimulation of vascular andlymphatic circulation would prevent the build-up of metabolic products, which are known tostimulate pain receptors (Proffit 1986).In a study on 93 orthodontic patients, White (1984) found that 63% of their subjects reported lessdiscomfort after chewing analgesic gum, however, lack of control group in this study raises thequestion of whether the reduction of pain was due to the analgesics or the chewing function.Transcutaneous electrical nerve stimulation (TENS) is another technique for pain control inorthodontics which according to Roth and Thrash (1986) dramatically decreased the delayed (morethan 12 hours after arch wire adjustment) pain response. Unfortunately, there was not anysignificant reduction of pain within the first 12 hours using this method. Low level laser has beenclaimed by many investigators to produce analgesic effects in various therapeutic and clinicalapplications (Plog 1980, Midda and Renton-Harper 1991). The mechanism of laser analgesia hasnot been established, but it has been attributed to its anti-inflammatory effects (Harris 1991). Lowlevel laser therapy has been applied for the treatment of pain related to orthodontic activations butwithout success (Lim et al. 1995). Blechman (1998) reported of the possibility of pain free andmobility free orthodontics using magnetic force fields. Magnetic field is hypothesized to accelerateosteogenic rate and therefore, reduce tooth mobility and the related pain. However, the assumptionis based only on several reports by different clinicians. Up to date there is no systematic studypublished comparing the pain experience, tooth mobility and sensitivity between the toothmovements in the conventional approach and under magnetic fields. Further studies on the differentmechanisms of pain induction during tooth movement are needed to provide the essentialknowledge for its possible management. 19
  • 18. 3. AIMS OF THE PRESENT STUDYThe purpose of the present study was to assess the prevalence and significance of the painexperience reported by the patients at different stages of orthodontic treatment. It was alsoexamined to what extent the dental pulp sensitivity might be changed or affected by the treatment,and if such changes could explain part of the pain symptoms complained by patients. It washypothesized that the pain experienced during orthodontic tooth movement is strongest at the initialphase of the therapy and that it gradually decreases with time. Also it was presumed that the amountof tooth movement as a response to orthodontic forces is related to the tooth sensitivity asperception of pain experienced by the patients.The specific objectives were to study:1. The prevalence, intensity, quality and duration of pain/discomfort experienced by patients atdifferent stages of orthodontic treatment during different functions used as stimuli, by using astructured questionnaire,2. The effect of orthodontic treatment/forces on electrical thresholds and cold sensitivity of thedental pulp,3. The relationship between the subjective pain perception as reported in the questionnaire and painresponses in the clinical sensitivity tests,4. The relation of the subjective pain perception and the clinically assessed sensitivity to the amountof tooth movement. 20
  • 19. 4. SUBJECTS AND METHODS4.1. SubjectsThe study group consisted of 64 patients, 46 females and 18 males, with a mean age 26.4 years (SD11.1). The distribution of the age and gender of the subjects is shown in Table 1.Table 1. Age and gender distribution of the subjects. Age (yrs) Female Male Total (n=46) (n=18) (n=64) Mean 27.8 22.9 26.4 SD 11.7 9.0 11.2 Range 10.8-49.3 11.8-40.6 10.8-49.3The study subjects were not pre-selected but the sample was formed by consecutive cases frompatients who were willing to participate. Patients were included in this study at the beginning oftheir active orthodontic treatment before the insertion of fixed appliances. The deciduous teeth ofpatients who were in the late mixed dentition stage were not included in the measurements. The ap-pliances inserted were complete banded/bonded appliance of either one or both dental arches. Noadditional elements of fixed appliances, extraoral or functional appliances were used during thestudy. The study protocol was approved by the ethics committee of the Medical Faculty, Universityof Kuopio, Kuopio, Finland.4.2. Orthodontic mechanotherapies used for the study subjectsThree different fixed appliances were used: Standard edgewise technique for six patients, WickAlexander technique for 30 patients and Viazis technique for 28 patients. Because of the smallnumber of participants in the standard edgewise bracket group (n=6), this group was not included inthe comparison of different techniques but for all other comparisons. 21
  • 20. Elastics for separating the first molars before banding (3M Unitek, Alastik Separator Modules) wereplaced and left at the mesial and distal contacts of the first permanent molars in each of the fourquadrants for a three day period.The three different types of fixed appliances used a 0.018″ bracket slot size, were: the Viazis(OrthoSystem Inc., Plano, TX), the Alexander MINI WICK (Ormco Corporation), and the Standardedgewise (Unitek/3M) brackets. The characteristics of the different mechanotherapies in producingorthodontic tooth movement have been described (Viazis 1995, 1998, Alexander 1986)- Viazis Bioefficient therapy (Viazis 1995) with a triangular bracket design, which is a combinationof a twin bracket at the lower half and a single bracket type at the upper half. The bracket slot iselevated so that the wire may come in contact with the extensions (the bracket elbows), thusproviding control for tipping movements. The longer the interslot distance, the lower the wirestiffness. The Viazis mechanotherapy incorporated a square initial archwire, 0.018″ x 0.018″ Heatactivated, Ionguard (Nitrogen substitution of the top 3 μmm of Nickel of the archwire surface),Bioforce Sentalloy (GAC International, Inc.). These archwires have been described to demonstratea differential force delivery increasing progressively from 80 grams of force anteriorly, up to 320grams of force in the posterior region. Heat activated property refers to that a decrease intemperature allows the archwire to be in the martensinic phase, which provides ease of handlingduring the archwire engagement to the bracket. At the oral temperature, austensinic phase resumesthe original arch form (shape memory). Additionally, in this technique in premolar extraction casesNiti closed coil springs, Tension w/hooks M (GAC International, Inc.) were used in conjunctionwith the initial archwire. The closed coil delivers 150 grams of force for canine retraction (GACInternational, Inc.). The objective of this mechanotherapy is to start the space closure as soon aspossible and to make the transition towards the finishing stainless steel wire within four to sixmonths of active therapy.- Alexander technique has a twin bracket design for the maxillary incisors in combination withsingle brackets with wings on the rest of maxillary and mandibular dentition. A round 0.016″Superelastic Thermalloy Niti initial archwire (RMO) was used. This archwire has been described tohave a force delivery of 80 grams of force throughout the arch (Alexander 1986). In both extractionand non-extraction treatments it is recommended the initial archwire to be activated for the next twoor three appointments before changing to an archwire with higher forces, for example, a round0.016″ stainless steel wire, to continue the alignment and leveling or the sliding mechanics forcanine retraction. 22
  • 21. - Standard edgewise technique, incorporated the same initial archwire and mechanotherapyapproach as that of the Alexander technique, the difference being the types of the brackets used.The age and gender distribution of the subjects in the Alexander technique (n=30) and the Viazis(n=28) technique is shown in Table 2.Table 2. Age and gender distribution of the subjects treated with the two different types of fixedappliances. Alexander technique Viazis technique Age (yrs) Female Male Total Female Male Total (n=23) (n=7) (n=30) (n=19) (n=9) (n=28) Mean 28.8 27.4 28.5 25.9 21.5 24.5 SD 11.3 9.5 10.7 11.6 7.9 10.6 Range 10.8-45.9 12.3-40.6 10.8-45.9 11.4-45.4 11.8-33.2 11.4-45.44.3. The questionnaireThe intensity, quality and duration of pain symptoms subsequent to the placement and activation ofthe orthodontic appliances were assessed in a longitudinal series of questionnaires. The question-naires (Appendix I) were given to each patient with a request to return them for the nextappointment. The patients were given oral as well as written instructions on how to complete thequestionnaire. Neither prescription for pain medication nor analgesics were dispensed to thepatients. However, they were free to take any medication they felt necessary. They were asked tomark at the top of the questionnaire the brand name, dose and timing of the medication they hadpossibly taken. In the questionnaire the occurrence of pain in connection with seven differentstimuli related to everyday life was included, namely: cold food/drink, hot food/drink, sweets, toothbrushing, mastication of food, fitting the anterior teeth together and fitting the posterior teeth to-gether. The patients were requested to fill out the questionnaire every morning for three days afterinsertion of orthodontic separators, after initial archwire insertion and after activation of the 23
  • 22. archwire. The pain intensity was scored on a 0-3 scale on each of the first three days after the threeaforementioned stages of the orthodontic treatment (see protocol page 32). The scores were definedas follows:0 = No pain,1 = Mild pain,2 = Moderate pain,3 = Severe/intolerable pain.The descriptors which were used to indicate the quality of pain in the questionnaire were as follow;1) sore, 2) shooting, 3) dull and 4) ache. Duration of pain was divided into two groups of short (S)(lasting not more than a few seconds) and long (L) lasting pain (clearly outlasting the time of thestimulus).The pain experience related to each stimulus was estimated for its intensity, quality and duration(Table. 3). Stimulus Sore Shooting Dull Ache Duration Duration Duration Duration Fitting 0 S 0 S 0 S 0 S front teeth 1 L 1 L 1 L 1 L together 2 2 2 2 3 3 3 3Table 3. An example of a patient’s response to pain from fitting the front teeth together after theinsertion of the initial archwire. The patient reported that the teeth were sore and the evokedsensation was mild and short lasting.The intensity of pain related to each pain descriptor was calculated on the basis of all responsesgiven by the patients in all questionnaires and each stimuli. The mean values for each descriptor arepresented in Figure 1. Although not statistically significant, there was a clear trend, the order of theintensity scores for different descriptors was: sore<shooting<dull<ache. Figure 2 shows the relationbetween the intensity and the duration of the reported pain. 24
  • 23. 3 2 Intensity of pain 1 0 sore shooting dull ache Quality of painFigure 1. The overall relations between the quality and the intensity of the reported pain. 3 Intensity of pain (0-3) 2 1 0 short long Duration of painFigure 2. The relations between the overall intensity and duration of the reported pain. 25
  • 24. On the basis of this comparison the pain quality descriptors were arranged in the following orderfrom the least intense to the most intense one; 1= sore, 2= shooting, 3= dull and 4= ache.Correspondingly, pain described as being of either short or long duration was given values of 1 and2, respectively. They were given these numerical values for the further analyses and used to form atotal pain score.For statistical analyses, an index describing the pain experience was formed by multiplying thenumerical values of the intensity (0-3), the quality (1-4), and the duration (1, 2) of pain.Thus the maximum pain scores were as follows:1) 3 x 4 x 2=24 PIS Pain Index for each Stimuli (one questionnaire)2) 24 x 7=168 PIQ Pain Index for one Questionnaire (seven stimulus)3) 24 x 7 x 3=504 PIStage Pain Index for one treatment Stage (three questionnaires)4) 24 x 6=144 PI2Stages Pain Index for each Stimuli at Two stages (six questionnaires)5) 24 x 9=216 TPIS Total Pain Index for each Stimuli at three stages (nine questionnaires)6) 24 x 7 x 9=1512 TPI Total Pain Index (seven stimuli and nine questionnaires)4.4. Clinical examinationA total of 907 teeth of the 64 subjects were examined in the clinical sensitivity tests, which includedmeasurements of the dental electrical thresholds and cold sensitivity. The teeth were dried andisolated with cotton rolls. The measurements were performed for each tooth starting from themaxillary right first molar and ending up with the mandibular right first molar (maximum of 24teeth per patient). Thus five to ten minutes of recovery period was allowed between stimulus appli-cations for each tooth. Any enamel/dentin irregularities or caries/fillings were avoided as sites ofstimulation. The tooth number and the surface were noted on the patients´ chart so that the samespot could be stimulated during all appointments. Teeth with crowns, root canal fillings and/or withextensive fillings were excluded. If the molars were to be banded, they were excluded from thesensitivity tests after banding due to the difficulties in finding an exact spot for stimulation. Thusthose cases were included only in the first set of the questionnaire involving the separation of the -molar and patient’s response during the following three days. Altogether 5-7 hours was spentcollecting the data from each patient. 26
  • 25. 4.4.1. Dental electrical threshold measurementElectrical thresholds were measured with a constant current electrical stimulator (Bofors PulpTester, Bofors, Sweden) in µA, (Fig.3). The stimulator gives 10 ms cathodal square wave pulses at5 Hz frequency. The stimulator tip was 2 mm in diameter and made of conductive rubber. The tip ofthe stimulator was placed in contact with the incisal third of the lingual/palatal surfaces of theincisors and lingual/palatal cusp tip of the premolars and the mesiolingual/palatal cusps of the firstmolars (Fig. 4). Stimulation of the cervical third close to the gingiva was avoided because of thedanger of the current leakage to the soft tissues with low resistance (Mumford and Björn 1962,Matthews and Searle 1974, 1976, Mumford 1982). Patients were instructed to stop the electricalcurrent by pushing the button on the handle as soon as they felt any sensation (prepain). Theelectrical threshold of each tooth was measured twice, and the mean value of the two measurementswas used for further analysis of data. In cases in which the difference between the two readings wasmore than 5 µA in incisors, 15 µA in canines and premolars and 25 µA in molars, the lowervalues were selected. 27
  • 26. Figure 3. The constant current electrical stimulator used to measure the dental electrical thresholds(Bofors Pulp Tester, Bofors, Sweden).Figure 4. The electrical stimulator probe in contact with the incisal third of the palatal surface of amaxillary central incisor. 28
  • 27. Figure 5. The thermal stimulator used to test the cold sensitivity of the studied teeth.Figure 6. The cold stimulator probe in contact with the cervical third of the facial surface of amaxillary lateral incisor. 29
  • 28. 4.4.2. Testing thermal sensitivity of the teethMethods for testing sensitivity of tooth, originally developed for studies on dentin hypersensitivity(Kontturi-Närhi 1993, Kontturi-Närhi and Närhi 1993), were adopted for examination and evalu-ation of the tooth responses to orthodontic forces. An electrothermal device constructed in theTechnical Center of the University of Kuopio was employed for the purpose (Fig.5). Thestimulator´s probe had a feedback circuit for the control of the tip temperature at an accuracy of0.1ºC. The tip diameter was 2mm. Cold stimuli at 15ºC and 0ºC were applied to the teeth underexamination. The tip of the probe was precooled to the desired temperature and then placed on thecervical third of the facial surface of each tooth (Fig. 6). In each stimulation trial the cold probe waskept in contact with the tooth for a maximum of 2 seconds. No extra pressure was exerted on thetooth surface. Prior to testing, patients were instructed to raise the right hand at the instant he/shefelt the first sensation. As soon as the patient gave a positive response, the stimulation of the toothwas discontinued.The intensity of the induced pain was assessed with a 100 mm Visual Analogue Scale (VAS)(Huskisson 1983, McGrath 1986). The left end of the scale indicated "no pain" and the right end"intolerable pain" (Fig. 7). Patients were requested to place a vertical mark on the VAScorresponding to the intensity of the pain they experienced. They were able to see only one VAS ata time.The distance of the mark from the left end of the scale was then taken to represent the VAS painscore.No pain Intolerable painFig. 7. The visual analogue scale (VAS) used in the present study. The length of the scale was 100mm.4.5. Measurement of tooth movement from hard stone castsDental casts were made from alginate impressions taken before the treatment and a second set threemonths after the placement of the initial archwire. Severity of malocclusion was then measuredusing the Irregularity Index, defined as the summed displacement of adjacent anatomic contact 30
  • 29. points (Little 1975) for the maxillary and mandibular anterior segments (canine-canine).Furthermore, in extraction cases the movement of the teeth moved into extraction space wasmeasured. The measurements were carried out with a Mitutoyo digital caliper (Mitutoyo Mfg. Co.,Ltd., Japan) to the nearest 0.1 mm. For intraexaminer consistancy, the measurements included theIrregularity Index as well as the amount of tooth movement into the extraction spaces, twentyrandomly selected dental casts were measured three times with a three weeks intervals. Theintraclass correlation coefficient (Selkäinaho 1983) was used for the three repeated measurementsof the dental casts. The values of ICC were high for both measurements (ICC 0.99, 95% CI 0.998,.0999). There was no statistically significant difference between the two groups with regards to theanterior crowding prior to the orthodontic treatment (by t-test). 31
  • 30. 4.6. Study protocolThe examination of the subjects was divided into five stages (I-V) as shown in the following table:Stage Orthodontic procedure Cold sensitivity and Questionnaire electrical pulp testsI Orthodontic separators Initial (T1), before Three (one/day, S1, S2, S3) (S) separation of molarsII Banding/Bonding & Second (T2) Three (one/day, W1, W2, W3)(3 days after stage I) initial archwire (W)III Third (T3)(3 days after stage II)IV Before activation of the Fourth (T4) Three (one/day, A1, A2, A3)(A month after stage III) archwire (A)V Final (TF)(3 days after stage IV)T1 corresponds to the measurements of the cold sensitivity and electrical pulp tests, before theinsertion of orthodontic separators. T2 is the pulpal tests after three days of orthodontic separation ofmolars. T3 is the pulpal tests after three days of bonding orthodontic appliances. T4 is the pulpaltests before activation of archwires and TF is the final pulpal tests, three days after activation ofarchwires. 32
  • 31. 4.7. Statistical methodsIn analyzing data from the questionnaire, chi-square test and Z-test were applied in comparing thefrequencies of the categorical variables at different stages of orthodontic treatment. The Wilcoxonmatched-pairs signed-ranks test was used to compare the changes in the pain intensity (0-3), quality(1-4) and duration (1,2), at different days (1,2,3) and stages (separation of the first molars, initialarchwire insertion and the archwire activation) of the orthodontic treatment. The differencesbetween the means of the parametric variables were analyzed by Student’s t-test. Pearsoncorrelation coefficient was used when analyzing the relationships between the clinical measurements(cold sensitivity at 15ºC and 0ºC, electrical thresholds), and the subjective responses to thedifferent orthodontic procedures (separation of the first molars, initial archwire insertion and thearchwire activation). Multiple regression analysis was used to estimate the associations between thescores of the index of the reported pain and clinical measurements for each tooth including coldstimulation (VAS values in mm) and the electrical thresholds in µA, considering the possibleeffects of age (years), gender (0=female, 1=male), type of brackets (1=Alexander, 2=Viazis) and theuse of analgesics (0=no, 1=yes), one or both jaws treatment (0=one, 1=both), and extraction (1=no,2=yes). In analyzing the clinical data (questionnaire study excluded), and measurements Student’s t-test, paired t-test and Pearson correlation coefficients were used. The statistical significance levelwas taken at p≤0.05, in all the tests performed. 33
  • 32. 5. RESULTS5.1. Subjective pain experience during orthodontic treatment as reported in thequestionnairesThe overall response rate for the questionnaires was 98.6%. Altogether seven questionnaires weremissing, four from the initial archwire placement and three from the activation phase. Throughoutthe entire study, five appointments were compromised for two days interval instead of three becauseof the adult patients´ working schedules (for these patients only the available data were used andanalyzed). Two patients were excluded, one moved abroad and the other had difficulties incomplying with the study requirements. Thus the number of subjects included in the analyses was64. There was a financial incentive (50% discount of the total orthodontic treatment costs), for thosewho participated in the study. We were able to recruit 66 subjects (two did not complete the study)out of 68 (that is 97% of the total). Subjects reflect a reasonable representation of our practice.5.1.1. Prevalence of painPrevalence of reported pain during the first three days after different orthodontic procedures fordifferent stimuli are shown in Table 4. The prevalence was higher after initial archwire insertion(W1, W2, W3) than after separation of molars (S1, S2, S3) and archwire activation (A1, A2, A3), inconnection with all the stimuli except for sweets at S1 compared to W1. In general, the prevalencedecreased from the first through the second to the third day. The exceptions were for coldfood/drink and fitting posterior teeth together between A1 and A2, for sweets, mastication of food,and fitting anterior teeth together between W1 and W2, and also for tooth brushing between A2 andA3. Prevalence of pain was more clearly highest for mastication of food and fitting anterior teethtogether during the second day after the initial archwire, in 93.2% and 89.9%, respectively. Painwas also very common for fitting the posterior teeth together during W1 and W2, 83% and 81%,respectively. There were no statistically significant differences except for W1/W3 in coldfood/drink and S1/S3 in tooth brushing (p<0.05= Z value at 1.2-3.8).The highest frequency of pain was reported after the insertion of initial archwire, in relation to allitems namely, mastication of food in 93.2%, fitting anterior teeth in 82.7%, fitting posterior teeth in78.6%, tooth brushing in 47.6%, cold in 27.4%, hot in 22.3% and sweets in 9.8% of all subjects.The differences in the prevalence of the reported pain between the first three corresponding days of 34
  • 33. different orthodontic procedures (Table 5) related to all other items except for sweets and hotfood/drink at W1/A1, and sweets at S1/W1, were statistically significantly higher at the first dayafter initial archwire insertion (W1) compared to both the first days after separation of molars (S1)and the archwire activation (A1). The prevalence of the experienced pain (Table 5) was quitesimilar on the first days after molar separation (S1) and archwire activation (A1) with only twoitems, namely, fitting anterior and posterior teeth together showing statistically significantdifferences.Table 4. The prevalences of pain reported by 64 orthodontic patients during the first three days aftereach orthodontic procedure, namely, separation of the molars (S1, S2 and S3), initial archwireplacement (W1, W2 and W3), and the first archwire activation (A1, A2 and A3) for different itemsof the questionnaire. Stimulus Days after separation Days after initial Days after activation archwire of archwire S1 S2 S3 W1 W2 W3 A1 A2 A3 % % % % % % % % % Cold food/drink 14.3 11.6 9.5 35.6 28.8 17.9 13.5 16.7 9.8 Hot food/drink 9.5 7.0 2.4 25.4 23.7 17.9 12.1 8.3 6.6 Sweets 9.5 7.0 7.1 8.5 11.9 8.9 6.9 5.0 4.9 Tooth brushing 28.6 20.9 11.9 50.8 49.2 42.9 34.1 20.0 24.6 Mastication of food 50.0 55.8 42.9 88.1 93.2 89.3 56.9 53.3 49.2 Fitting anterior teeth 14.3 14.0 11.9 79.7 89.8 78.6 51.7 43.3 41.0 Fitting posterior 61.9 58.1 45.2 83.1 81.4 71.4 27.6 30.0 24.6 teeth 35
  • 34. Table 5. The statistical significance of the differences in the prevalence of the reported painbetween the first three days of different orthodontic procedures. By Z-test. (P<0.05, Z value 1.2-3.8and P<0.01, Z value 3.8-5.6 and P<0.001, Z value>5.6). S1/W1 S2/W2 S3/W3 S1/A1 S2/A2 S3/A3 W1/A1 W2/A2 W3/A3 P<0.01 P<0.05 P>0.05 P>0.05 P>0.05 P>0.05 P<0.01 P>0.05 P>0.05Coldfood/drink P<0.05 P<0.01 P<0.001 P>0.05 P>0.05 P>0.05 P>0.05 P<0.05 P<0.05Hotfood/drink P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05 P>0.05Sweets P<0.01 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.05Toothbrushing P<0.001 P<0.001 P<0.001 P>0.05 P>0.05 P>0.05 P<0.001 P<0.001 P<0.001Mastication of food P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001 P<0.001Fittinganteriorteeth P<0.01 P<0.01 P<0.01 P<0.001 P<0.01 P<0.05 P<0.001 P<0.001 P<0.001Fittingposteriorteeth 36
  • 35. 5.1.2. The intensity, quality and duration of the reported painBased on all pain reports, pain intensity was most frequently reported to be mild (62.5%) followedby moderate (28.5%) and severe (9%) pain respectively. The distribution of the intensity of thereported pain symptoms during the first three days after different orthodontic procedures, in relationto each stimuli included in the questionnaire, is presented in Table 6. During the three days after theinsertion of initial archwire the corresponding distribution of the reported pain intensity was mild52.7%, moderate 33.9% and severe 13.4%. There were no reports of severe pain during the firstthree days after separation of molars and wire activation in connection with cold and hot food/drink,sweets and tooth brushing. This coincides with the high "no pain" reports related to theabovementioned items. The highest prevalence of severe pain was found after the initial archwireinsertion, namely on the first day after the procedure mastication of food was reported to causesevere pain most frequently, by 25.4% of the subjects. Generally reports of the severe pain weremostly related to the three most frequently reported items: mastication of food, and fitting anteriorand posterior teeth together respectively. 37
  • 36. Table 6. The distribution of orthodontic patients who experienced pain according to the intensity ofthe experienced pain during the first three days after each orthodontic procedure, separation ofmolars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3). Days after separation Days after initial archwire Days after activation of the archwire S1 S2 S3 W1 W2 W3 A1 A2 A3 n n n n n n n n n % % % % % % % % %Cold food/drink(n) 11 10 9 35 18 11 10 10 6mild pain 83.2 100 100 61.8 70.5 90.0 78.0 80.1 100moderate pain 16.8 0 0 23.9 23.6 0 22.0 19.9 0severe pain 0 0 0 14.3 5.9 10.0 0 0 0Hot food/drink(n) 9 7 5 16 15 11 8 5 4mild pain 100 100 100 53.6 64.3 100 85.8 100 100moderate pain 0 0 0 40.0 35.7 0 14.2 0 0severe pain 0 0 0 6.7 0 0 0 0 0Sweets(n) 9 7 8 5 7 5 4 3 3mild pain 50.0 0 66.6 40.0 71.4 60.0 100 100 100moderate pain 50.0 100 33.4 0 0 40.0 0 0 0severe pain 0 0 0 60.0 28.6 0 0 0 0Tooth brushing(n) 19 14 8 33 32 27 15 13 16mild pain 83.2 89.0 80.0 70.0 58.6 70.9 71.4 83.5 86.6moderate pain 16.8 11.0 20.0 16.7 37.9 24.9 28.6 16.5 13.4severe pain 0 0 0 13.3 3.5 4.2 0 0 0Mastication of food(n) 32 36 28 56 60 57 36 34 31mild pain 63.9 53.1 77.6 23.0 29.0 40.0 62.8 74.9 80.0moderate pain 24.4 32.7 11.2 48.1 51.0 48.0 21.0 21.9 20.0severe pain 11.7 14.2 11.2 28.9 20.0 12.0 16.2 3.2 0Fitting anterior teeth(n) 9 8 7 51 57 50 33 28 26mild pain 49.6 83.4 80.0 42.5 52.8 52.3 63.4 65.3 88.0moderate pain 33.6 16.6 20.0 44.7 32.0 34.0 30.0 30.7 12.0severe pain 16.8 0 0 12.8 15.2 13.7 6.6 4.0 0Fitting posterior teeth(n) 40 37 29 53 52 46 18 19 16mild pain 61.6 68.0 79.0 61.2 64.6 62.5 68.8 72.3 86.6moderate pain 34.6 32.0 21.0 28.5 28.5 27.5 31.2 27.7 15.4severe pain 3.8 0 0 11.3 11.3 10.0 0 0 0The quality of the reported pain as indicated by the pain descriptors during the first three daysafter each orthodontic procedure, regarding each item included in the questionnaire is presentedin Table 7. According to the reports sore (65%) was the most frequent descriptor followed bydull (15.5%), shooting (9.5%) and ache (9.5%). During the three days after the insertion ofinitial archwire the corresponding distribution of the pain descriptors were 65.2% for sore,14.6% for shooting, 12.1% for dull and 8.1% for ache.Regarding the duration of the reported pain during the first three days after different orthodon-tic procedures, for different stimuli, in general pain was mostly short lasting in 85% of thereports (Table 8). During the three days after the insertion of initial archwire the proportion of 38
  • 37. short and long lasting pain were 75.2% and 24.8% respectively. The differences in the reportedduration of pain (short vs. long), were statistically significant when comparing the three daysafter archwire insertion to the corresponding days after archwire activation in all items exceptfor cold at W2/A2 and sweets at W3/A3.Wilcoxon Matched-Pairs Signed-Ranks Test was used to study the differences of the intensity,quality and duration of the reported pain in connection with each item between the first threedays after each orthodontic procedure (Table. 9). No statistically significant difference wasfound between S1/S2 in the pain reports of any item. In general most of the significantdifferences between the days examined in connection with the intensity, quality and duration ofthe reported pain were found between W1/W3 followed by W2/W3 and S1/S3 and S2/S3,respectively. Differences in the intensity, quality and duration of the reported pain inconnection with cold food/drink were highest and found to be statistically significant betweenW1/W3 and W2/W3. Comparison between the differences of the reported pain during the firstthree days after archwire activation (A1, A2 and A3) showed statistically significant differencesonly with regards to fitting front teeth together. Taking sweets was the only item with nostatistically significant differences of the reported pain between the days tested.Wilcoxon Matched-Pairs Signed-Ranks Test was also used to study the differences of theintensity, quality and duration of the reported pain in connection with each item between thefirst three days of different orthodontic procedures (Table. 10). Taking sweets was the onlyitem with no statistically significant differences in the reported pain between the days tested. Ingeneral most of the significant differences were found between W1/A1 followed closely byS3/W3, W3/A3, S1/W1, S2/W2 and W3/A3, respectively. Comparison between the differencesof the reported pain during the first three days after archwire activation and separation ofmolars (S1/A1, S2/A2 and S3/A3) showed statistically significant differences only with regardsto fitting anterior and posterior teeth together. 39
  • 38. Table 7. The distribution of the quality of experienced pain of 64 orthodontic patients whoexperienced pain during the first three days after each orthodontic procedure, separation of molars(S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3). Days after separation Days after initial archwire Days after activation of the archwire S1 S2 S3 W1 W2 W3 A1 A2 A3 n n n n n n n n n % % % % % % % % %Cold food/drink (n) 9 7 6 23 18 11 10 11 6sore 49.6 60.0 25.0 42.8 41.2 39.7 22.0 19.9 16.3shooting 32.5 40.0 50.0 42.8 41.2 30.2 44.5 50.0 50.0dull 17.9 0 25.0 4.8 11.7 20.1 33.5 19.9 33.7ache 0 0 0 9.6 5.9 10.0 0 10.2 0Hot food/drink (n) 6 4 2 16 15 11 8 5 4sore 74.7 100 100 53.3 50.0 59.8 28.3 20.5 24.6shooting 0 0 0 20.0 28.6 20.1 28.3 39.7 50.8dull 25.3 0 0 20.0 21.4 10.1 43.4 39.7 24.6ache 0 0 0 6.7 0 10.0 0 0 0Sweets (n) 6 4 4 5 8 5 4 3 3sore 74.7 67.1 66.6 80.0 85.7 79.8 100 100 100shooting 25.3 32.9 33.4 20.0 14.3 20.2 0 0 0dull 0 0 0 0 0 0 0 0 0ache 0 0 0 0 0 0 0 0 0Tooth brushing (n) 18 13 8 33 31 27 15 13 16sore 83.2 89.0 79.8 80.0 82.7 79.2 57.3 66.5 67.0shooting 8.4 0 0 0 10.4 16.6 7.1 0 6.5dull 8.4 11.0 20.2 10.0 6.9 4.2 14.1 25.0 20.0ache 0 0 0 10.0 0 0 21.5 8.5 6.5Mastication of food (n) 32 36 24 56 60 57 36 34 31sore 45.9 49.9 66.6 59.6 69.0 72.0 72.8 65.5 76.6shooting 14.2 12.5 5.6 5.8 3.6 7.9 3.0 3.2 0dull 19.0 29.2 16.5 13.5 14.6 14.0 15.1 21.9 16.6ache 20.9 8.4 11.3 21.1 12.8 6.1 9.1 9.4 6.8Fitting anterior teeth (n) 9 9 9 51 58 50 33 28 26sore 49.6 66.8 33.6 57.4 60.3 77.2 50.0 65.3 68.0shooting 0 0 16.8 6.4 7.6 4.6 10.0 7.6 3.9dull 33.6 16.6 49.6 17.0 15.1 11.3 16.6 15.5 20.0ache 16.8 16.6 0 19.2 17.0 6.9 23.4 11.6 8.1Fitting posterior teeth (n) 40 37 29 53 52 46 27 19 16sore 57.7 59.9 57.8 59.2 70.8 70.0 81.5 94.3 80.1shooting 7.7 8.1 5.3 0 2.1 5.0 0 0 0dull 15.3 19.9 31.5 28.5 16.7 15.0 12.3 5.7 13.4ache 19.3 12.1 5.4 12.3 10.4 10.0 6.2 0 6.5 40
  • 39. Table 8. The distribution of the duration of experienced pain of 64 orthodontic patients whoexperienced pain during the first three days after each orthodontic procedure, separation ofmolars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 andA3). Days after separation Days after initial Days after activation archwire of the archwire S1 S2 S3 W1 W2 W3 A1 A2 A3 n n n n n n n n n % % % % % % % % %Cold food/drink (n) 9 7 6 23 18 11 10 11 6short 66.5 80.2 100 76.1 88.2 89.9 100 89.8 100long 33.5 19.8 0 23.9 11.8 10.1 0 10.2 0Hot food/drink (n) 6 4 2 16 15 11 8 5 4short 74.7 100 100 79.9 92.8 89.9 100 100 100long 25.3 0 0 20.1 7.2 10.1 0 0 0Sweets (n) 6 4 4 5 8 6 4 3 3short 74.7 100 100 40.0 71.4 100 100 100 100long 25.3 0 0 60.0 28.6 0 0 0 0Tooth brushing (n) 18 13 8 33 31 27 15 13 16short 100 100 100 76.6 86.2 91.6 85.9 91.5 100long 0 0 0 23.4 15.8 8.4 14.1 8.5 0Mastication of food (n) 32 36 27 57 60 57 36 34 31short 81.0 83.3 94.4 53.8 65.6 82.0 94.0 96.8 96.7long 19.0 16.7 5.6 46.2 34.4 18.0 6.0 3.2 3.3Fitting anterior teeth (n) 9 9 9 51 57 50 33 28 26short 66.4 83.4 100 68.0 79.3 86.4 86.6 96.1 100long 33.6 16.6 0 32.0 20.7 13.6 13.4 3.9 0Fitting posterior teeth (n) 30 37 29 53 52 46 18 19 16short 73.0 84.0 94.7 79.6 87.5 85.0 93.8 100 100long 27.0 16.0 5.3 20.4 12.5 15.0 6.2 0 0 41
  • 40. Table 9. The statistical significance of the differences in the intensity, quality and duration of the reported pain during the first three days after each orthodontic procedure, separation of molars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 and A3). By Wilcoxon Matched-pairs Signed-Ranks Test. S1/S2 S1/S3 S2/S3 W1/W2 W1/W3 W2/W3 A1/A2 A1/A3 A2/A3Cold food/drink Intensity .41 .18 .56 .06 .003 .029 .70 .06 .06 Quality .50 .58 1.0 .18 .032 .48 .46 .19 .10 Duration .52 .15 .41 .07 .005 .032 .41 .08 .06Hot food/drink Intensity .32 .18 .32 .61 .025 .012 .18 .16 .56 Quality .32 .16 .32 .56 .37 .75 .18 .17 .41 Duration .16 .16 .32 .78 .16 .10 .16 .18 .56Sweets Intensity .16 .59 .58 1.0 .16 .10 .32 .56 1.0 Quality .08 .74 1.0 .16 1.0 .16 .32 .56 1.0 Duration .18 .48 1.0 .65 .18 .10 .32 .56 1.0Tooth brushing Intensity .16 .019 .08 .83 .11 .09 .16 .36 .41 Quality .16 .019 .08 .000 .10 .036 .13 .35 .32 Duration .18 .014 .08 .28 .033 .16 .28 .36 .70Mastication of food Intensity .44 .18 .014 .65 .07 .023 .47 .11 .85 Quality .86 .038 .011 .006 .040 .31 .85 .12 .12 Duration .74 .09 .011 .54 .016 .002 .25 .052 .26Fitting anterior teeth Intensity .27 .75 .35 .60 .07 .36 .08 .005 .050 Quality .71 1.0 .68 .09 .012 .71 .021 .015 .87 Duration .71 .46 .71 .81 .08 .040 .041 .023 .46Fitting posterior teeth Intensity .11 .002 .027 .46 .48 .16 .64 .18 .22 Quality .21 .09 .08 .000 .013 .08 .65 .77 .79 Duration .07 .005 .033 .32 .06 .27 .77 .38 .38 42
  • 41. Table 10. The statistical significance of the differences in the intensity, quality and duration ofthe reported pain during the first three days after each orthodontic procedure, separation ofmolars (S1, S2 and S3), initial archwire (W1, W2 and W3), archwire activation (A1, A2 andA3). By Wilcoxon Matched-pairs Signed-Ranks Test. S1/W1 S2/W2 S3/W3 W1/A1 W2/A2 W3/A3 S1/A1 S2/A2 S3/A3Cold food/drink Intensity .006 .027 .41 .009 .09 .09 .80 .56 .56 Quality .034 .18 .59 .054 .64 .20 .72 .28 .41 Duration .028 .11 .31 .003 .09 .09 .55 1.0 .56Hot food/drink Intensity .021 .005 .034 .015 .005 .034 1.0 .65 1.0 Quality .22 .13 .033 .16 .16 .09 1.0 1.0 1.0 Duration .058 .005 .035 .025 .007 .035 .48 .65 1.0Sweets Intensity .70 .68 .70 .46 .20 .41 .33 .21 .48 Quality .56 .70 .70 .70 1.0 .41 .48 .48 .48 Duration .70 .65 .56 .46 .21 .56 .48 .65 .65Tooth brushing Intensity .003 .000 .000 .000 .000 .017 .87 1.0 .09 Quality .002 .67 .002 .10 .59 .39 .25 .55 .08 Duration .001 .000 .000 .000 .000 .034 .76 1.0 .10Mastication of food Intensity .000 .000 .000 .000 .000 .000 .28 .24 .08 Quality .09 .83 .001 .001 .21 .003 .67 .41 .89 Duration .000 .000 .000 .000 .000 .000 .82 .20 .82Fitting anterior teeth Intensity .000 .000 .000 .000 .000 .000 .019 .012 .012 Quality .000 .000 .000 .008 .051 .015 .003 .010 .06 Duration .000 .000 .000 .000 .000 .000 .013 .026 .012Fitting posterior teeth Intensity .11 .050 .001 .000 .000 .000 .014 .036 .13 Quality .21 .57 .042 .000 .002 .001 .004 .004 .12 Duration .27 .08 .011 .000 .000 .000 .007 .022 .19 43
  • 42. The intensity in relation to different pain descriptors and duration of the reported pain is shown inFigure 8. Results are based on the combination of the scores, from the seven items throughout threedays of the three stages of the treatment (Total Pain Index, TPI, page 26 ), thus describing the painexperienced during the study period. 3 2 Intensity of pain short long 1 0 sore shooting dull ache Quality of painFigure 8. The relationship between the intensity, quality and duration of the pain reports given bythe subjects (Total Pain Index, score = 0-1512, page 26) during orthodontic treatment. The intensityvalues are based on (0=no pain, 1=mild pain, 2=moderate pain, 3=severe pain).5.1.3. Pain experienced during the three days subsequent to each orthodonticproceduresThe pain scores (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) for each of the firstthree days after different stages of the orthodontic treatment are shown in Fig. 9. The pain scoresafter each different treatment stages decreased during the first three days: after separation of molarsfrom 13.6 for S1, to 10.6 for S2 and further to 7.9 for S3. After initial archwire insertion the pain 44
  • 43. scores were 28.6 for W1, 23.5 for W2 and 16.8 for W3. The pain scores after the activation ofarchwire were 12.6 for A1, 9.6 for A2 and 7.9 for A3, respectively. Reduction of reported painsymptoms from the first day to the third was evident at all the stages, suggesting that the first day isthe most painful. Additionally, the initial archwire insertion was by far the most painful stage of thetreatment. The differences in the pain scores were statistically significant (z-test) for the combinedthree days, between separation of the first molars and initial archwire insertion and between initialarchwire insertion and its activation, the difference between the separation of molars and thearchwire activation stage was not statistically significant. The differences in the pain scores werestatistically significant within each treatment stage between; S1 and S2 (p=.040), S1 and S3(p=.008), W1 and W3 (p=.000), W2 and W3 (p=.005), A1 and A3 (p=.008) and among differentdays in different stages of treatment as follows: S1 and W1 (p=.002), S2 and W2 (p=.000), S3 andW3 (p=.001), W1 and A1 (p=.000), W2 and A2 (p=.000), W3 and A3 (p=.005). 30 25 fitting back teeth 20 fitting front teeth mastication 15 tooth brushing sweet 10 hot cold 5 0 S1 S2 S3 W1 W2 W3 A1 A2 A3Figure 9. Total index values (Pain Index for one Questionnaire, PIQ, score=0-168, page 26) of theperceived pain for seven items for each of the three days after separation of the molars (S1, S2, S3),after initial archwire insertion (W1, W2, W3) and after wire activation (A1, A2, A3). 45
  • 44. 5.1.4. Pain experienced in relation to different stimuli of the questionnaireThe pain scores for each of the seven stimuli combined for different stages of orthodontic treatment(Total Pain Index for one Stimuli, TPIS, score=0-216, page 26) are presented in Figure 10. Sweetsgave the lowest score 1.7, followed by hot food/drink 6.2, cold food/drink 10.0 and tooth brushing10.4. The highest pain scores were found in response to masticationof food and fitting front or back teeth together, 33.8, 27.0 and 24.6, respectively. 50 separation 40 initial archwire 1st activation 30 20 10 0 t t n ld ho ee ng io et h et h co hi at te te sw us tic br nt ck as fro ba th m oo ng ng t fitti fittiFigure 10. The reported pain for each of the seven items combined for different stages of treatment(Total Pain Index for one Stimuli, TPIS, score=0-216, page 26). 46
  • 45. 5.1.5. The relationship between subjective pain reports and the analgesic consumption The proportion of subjects taking analgesics during the first three days after different stages of treatment is presented in Figure 11. Overall analgesic consumption in the sample was limited to two patients in the separation stage and archwire activation stages and to 15 patients after the initial archwire placement. More analgesics were consumed on the second day after both the separation of molars and the initial archwire than on the first day. During the W3 the use of the analgesics dropped, and none was needed during S3 and A3. 20 15 1st day% 10 2nd day 3rd day 5 0 Separation Initial First archwire activation Figure 11. Percentage of the patients (n=64) taking analgesics during the first days after separation of the molars, after initial archwire insertion and archwire activation. 47
  • 46. Proportion of subjects taking analgesics and that of subjects reporting any pain during each studiedday after different stages of orthodontic treatment are shown in Figure 12. Patients responding toany of the items were included, therefore the results from the questionnaire reflects either if therewas discomfort associated with different orthodontic procedures or not (yes or no). A correlation(r=0.35) between these two variables was low although statistically significant (p=.006). 100 Analgesic cosumption Pain reports 80 60 % 40. 20 0 S 1st S 2nd S 3rd W 1st W W 3rd A 1st A 2nd A 3rd 2ndFigure 12.The proportion (%) of subjects reporting pain and using analgesics during the first threedays after separation of molars (S), initial archwire insertion (W) and wire activation (A), (n=64).Patients who had taken medication, reported higher pain scores in connection with all items of thequestionnaire except for sweets when compared to those without medication, these differences werestatistically significant (t-test) only in fitting front (p=.006) and back (p=.026) teeth together. 48
  • 47. 5.1.6. Relationship between subjective pain reports and age, gender, ext-raction(s) and extent of treatmentThe difference between the Total Pain Index, TPI, maximum score=1512, of the patients under andabove 16 year of age was not statistically significant. However, the older group reported symptomsmore frequently and pain was of higher intensity and longer duration in response to mastication onthe second day after archwire activation (p=0.047) and initial archwire insertion (p=0.028),respectively.Gender and tooth extractions did not have significant effects on the pain reports. With the treatmentof both jaws more discomfort was reported in fitting front and back teeth together, however, thetotal pain scores between patients with both jaws treated and only one jaw treated did not differsignificantly.5.2. Clinical study5.2.1. Responses to cold stimulationProportion of responding teeth to cold stimulation at 15ºC and 0ºC at different stages of thetreatment is presented in Table 11. In some of the patients molars were bonded and not separatedfor the banding procedure. The later measurements from the banded molars were discontinued. Ahigher proportion of the teeth responded at 0ºC when compared to 15ºC, at all stages of thetreatment in all tooth groups examined. Statistically significant differences (Z-test) were foundbetween the proportion of responding teeth in 15ºC and 0ºC at different stages of treatment, namely;incisors and all teeth combined during all the different stages of treatment, premolars and caninesduring the initial (TI) and three days after the first archwire (TF). 49
  • 48. Table 11. Proportion of responding teeth to cold stimulation at 15 and 0ºC at different stages of orthodontic treatment. Stages of orthodontic 15ºC 0ºC treatment % n % n Initial (before treatment) incisors 10.4 33 38.7 122 premolars and canines 4.8 21 24.2 104 molars 1.3 2 20.0 30 all teeth 6.2 56 28.6 256 After separation (S3) molars 3.9 4 22.5 23 Archwire activation (W3) incisors 16.3 45 47.7 132 premolars and canines 9.6 36 27.5 103 molars 8.1 11 27.8 37 all teeth 11.7 92 34.6 272 Before activation incisors 13.3 37 41.2 113 premolars and canines 3.5 13 24.3 89 molars 3.1 4 27.6 35 all teeth 6.9 54 30.9 237 After activation (A3) incisors 17.3 49 38.4 109 premolars and canines 6.1 23 23.6 90 molars 2.3 3 19.5 25 all teeth 9.5 75 28.2 224In order to study the overall dental cold sensitivity at different stages of orthodontic treatment theresults from maxillary and mandibular teeth were combined and grouped in three; 1) incisors, 2)canines and premolars, and 3) molars. The mean VAS values in response to cold stimulation at15ºC for each tooth group at different stages of treatment are shown in Figure 13. The VAS ratings(SE) at the initial stage were 0.3 (0.3) in molars, 0.65 (0.2) in premolars and canines, 2.1 (0.6) in in-cisors. The VAS ratings were higher at three days after initial archwire insertion. The mean values(SE) were 4.0 (0.9) for incisors, 1.9 (0.5) for premolars and canines and 2.2 (1.0) for molars. 50
  • 49. mm 14 12 10 8 molars premolars and canines 6 incisors 4g3i. F1 2 0 I II III IV V Figure 13. The mean VAS pain ratings to cold stimulation at 15ºC in different tooth groups at different stages of the treatment (I = initial, II = separation of molars, III = three days after initial archwire insertion, IV = before wire activation and V = three days after activation). Maxillary and mandibular teeth were combined in each tooth group. The mean VAS values in response to cold stimulation at 0ºC for each tooth group at different stages of treatment are shown in Figure 14. The highest VAS ratings were recorded in the initial archwire insertion stage. The incisors demonstrating increased sensitivity throughout the study period, 10.7 (1.5) at the initial stage, 14.2 (1.8) at three days after initial archwire insertion, 13.8 (2.2) at activation and 12.7 (2.1) at three days after activation stage. The mean,(SE) in the molars increased from the initial 4.45 (1.2) to 9.3 (1.9) three days after initial archwire activation. Smaller changes were observed in the premolars and canines group during this study. 51
  • 50. mm 14 12 10 8 molars premolars and canine 6 incisors 4 2Fig . 14 0 I II III IV V Figure 14. The mean VAS pain ratings to cold stimulation at 0ºC in different tooth groups at different stages of the treatment (I = initial, II = separation of molars, III = three days after initial archwire insertion, IV = wire activation and V = three days after activation). Maxillary and mandibular teeth were combined in each tooth group. 5.2.1.1. Correlations between the VAS ratings to cold stimulation at 0ºC and 15ºC. The correlation between the VAS ratings to cold stimulation at 0 and 15ºC at different stages of treatment is presented in Table 12. Using paired t-test for the statistical analysis revealed that except for molars at the initial stage (p=.131) and three days after activation (p=.083), all other tooth groups at all the stages were at a statistically significant level. 52
  • 51. Table 12. Correlations (Pearson correlation coefficient) between the VAS values in response of different groups of permanent teeth to cold at 0 and 15ºC at different stages of orthodontic treatment. Treatment phase Molars Premolars and Incisors canines r r r (p) (p) (p) Before treatment 0.20 0.50 0.63 (.131) (.000) * (.000) * After separation of the first molars 0.32 (.044) * On the 3rd day after initial arch- 0.51 0.69 0.40 wire insertion (.000) * (.000) * (.002) * Before the activation of the 0.30 0.54 0.64 archwire (.033) * (.000) * (.000) * On the 3rd day after activation 0.25 0.70 0.77 (.083) (.000) * (.000) * The mean electrical thresholds of each tooth group with the maxillary and mandibular teethcombined at different stages of the treatment are shown in Figure 15. The mean thresholds (SE) we-re; 28.2 (2.2), 25.3 (2.3), 24.7 (2.2) and 25.5 (3.2) in molars, 19.3 (1.2), 17.2 (2.0), 17.8 (1.4), 17.1(1.2), in premolars and canines and 13.2 (0.9), 12.0 (0.9), 12.1 (1.0), 12.7 (1.1) in the incisors, res-pectively. The difference between the means was statistically significant (p=.031) in incisorsbetween the archwire activation and three days after wire activation. 53
  • 52. µA 35F. 5 g1 i 30 25 20 molars 15 premolars and canines incisors 10 5 0 I II III IV V Figure 15. The mean dental electrical thresholds in different tooth groups at different stages of the treatment (I = initial, II = three days after the separation of molars, III = three days after the initial archwire insertion, IV = before wire activation and V = three days after activation). Maxillary and mandibular teeth were combined in each tooth group. 5.3. Comparison of two different orthodontic mechanotherapies In general the differences in the prevalence of the pain between the two fixed appliances were small and statistically significant only in connection with some of the questionnaire items which altogether gave the most frequent pain reports. Such items were mastication, fitting anterior and posterior teeth together. Differences in the pain scores between different fixed appliances, during the initial archwire insertion and wire activation stage, in response to each item (Pain Index of one stimuli in two Stages, page 26) is presented in Table 13. No statistical significant difference was found. Mastication of food was reported to have the highest score in both fixed appliances in the combined initial archwire and wire activation stage. Followed by fitting anterior and posterior teeth together, respectively. 54
  • 53. Table 13. The reported pain scores during the initial archwire and wire activation stage (Pain Index of one stimuli in two Stages, page 26) for each of the items in different fixed appliances. Alexander technique Viazis technique p* mean SD mean SD Cold 9.8 14.5 11.9 19.6 .668 Hot 5.5 10.1 8.5 19.7 .507 Sweet 1.5 6.4 0.5 1.3 .486 Tooth brushing 9.4 17.8 12.8 19.8 .521 Mastication 25.9 27.0 31.5 27.5 .474 Fitting anterior teeth 24.3 27.7 30.0 31.4 .508 Fitting posterior teeth 15.8 21.7 20.9 19.1 .386* by t-test The reported pain scores from each of the days after the initial archwire (W1, W2, W3) and the wire activation (A1, A2, A3) were compared and no statistical differences were found in different fixed appliances. After the initial archwire insertion pain reports were more frequent, having higher score, in the Viazis technique than the Alexander. However, after the wire activation stage the pain scores were higher in the Alexander technique. The changes in the reported pain scores (Index 1, score=0-24) from the first three days after initial archwire to the corresponding days after wire activation of each item in different fixed appliances were studied and analyzed further. Difference of the pain reports was calculated by subtracting the pain scores at the initial archwire insertion from the reported pain scores during the wire activation. Generally the pain scores from the initial archwire to the wire activation have reduced more in the Viazis technique, being at a statistically significant level only on the first days during mastication. There was a reduction of pain scores from the initial archwire insertion to the archwire activation in response to all items but on the first days in sweets with Viazis technique also on the second and third days in tooth brushing with Alexander technique. 55
  • 54. 5.3.1. Dental cold sensitivity and electrical thresholds in two differentorthodontic mechanotherapies.The mean VAS ratings to cold at 15ºC at different stages of treatment in connection with thetwo different fixed orthodontic appliances were studied and analyzed further. Already at theinitial stage, before treatment, there was a statistically significant difference between the twosystem in premolars and canines (p=.014) and all teeth combined (p=.032). There was a statisti-cal significant differences in the corresponding values also three days after initial archwireinsertion (p=.013, p=.008) and at the activation of the archwire (p=.039, p=013) respectively.The mean VAS ratings in response to cold stimulation at 0ºC at different stages of treatment inreaction to the two different fixed orthodontic appliances were studied and analyzed further. Nostatistically significant differences were found between the two systems at the initial stage. Themean VAS values in the other stages of the treatment (three days after initial archwire, beforeactivation of archwire and three days after activation) were lower in the Viazis techniquecompared to the Alexander. With all the teeth combined the differences were statistically sig-nificant three days after initial archwire (p=.012), at activation (p=.017) and three days afteractivation (p=.003). The differences in the mean VAS ratings were also statistically significantin premolars and canines three days after initial archwire placement and three days after wireactivation (p=.024, p=.001) respectively and in molars (p=.035) three days after archwireactivation.The mean dental electrical thresholds related to the two different fixed orthodontic applianceswere studied and analyzed further. There were no statistically significant differences at theinitial stage between the two groups. However, at the activation stage all tooth groups were lesssensitive in the Viazis technique with the difference in the incisors (p=.034), premolars and ca-nines (p=.005) and all teeth combined (p=.000) being at a statistically significant level. Also asignificant difference was found three days after archwire activation, when the teeth werecombined (p=.020). This might as well point to, increased pulpal disturbances. 56
  • 55. 5.3.2. Tooth movements in two different orthodontic mechanotherapiesThe results from tooth movements with different fixed appliances, using the irregularity index,defined as the summed displacement of adjacent anatomic contact points (Little 1975) for theanterior (canine to canine) crowding showed no statistically significant difference between thetwo techniques, either before or after three months of fixed orthodontic treatment. The meancrowding values for each patient was used for statistical analysis. In extraction cases, patientstreated with the Viazis technique demonstrated the mean space closure at the third month to be2.8mm compared to less than 1mm using Alexander technique. 57
  • 56. 6. DISCUSSION6.1. Study subjectsThe sample was formed by consecutive cases from patients who were willing to participate. As seenin many practices of contemporary orthodontics (Gottlieb and Voges, 1984) the number of adult pa-tients seeking therapy is increasing. This explains the high mean age of 26.4 years of the study sam-ple. Because age distribution was rather wide age was included in the statistical analyses as aconfounding factor. Gender distribution was not even in the sample, female subjects were overpresented, as is the case in most orthodontic practices. The effect of gender was also controlledduring the statistical analyses, and proved not to have an effect on the results.Size of the study sample was adequate for this study design. Because of the small number ofparticipants, the six patients who were treated with standard edgewise technique were not includedin the statistical analysis as a separate group. When comparing the two different fixed orthodonticappliances there was no difference between the two study groups as regard to the age and gender.6.2. Measurement of the experienced pain6.2.1. The questionnaireMost of the existing literature on the pain and discomfort related to orthodontic treatment has con-centrated on the intensity of pain with different evaluating methods, i.e. the Verbal Rating Scale orthe Visual Analogue Scale.In the present study subjective pain symptoms subsequent to different stages of orthodontictreatment were recorded using the questionnaire structured to include the intensity, quality and theduration of the experienced pain. Attempts were made to structure the questionnaire as simple aspossible to minimize the difficulties usually involved with filling out questionnaires especiallyregarding the youngest study subjects. To avoid a large volume of questionnaires and patients con-fusion, considering the longitudinal nature of this study, it was decided to combine the intensity,quality and duration of the pain symptoms in one questionnaire. The same form was filled out bythe patients during three consecutive days after each orthodontic procedures, namely afterseparation of first molars, insertion of the initial archwire and after the first archwire activation. 58
  • 57. Cooperation from the patients during the study was excellent, especially considering the time andeffort required for the completion of the repeated clinical tests and questionnaires during differentstages of treatment.Orthodontic tooth movement is believed to cause varying pain and discomfort to patients (SBU2005). The first day after each orthodontic procedure has been suggested as being associated withthe most discomfort experienced (Tayer and Burek 1981, Brown and Moerenhout 1991, Jones andChan 1992, Scheurer et al. 1996, Yozgatian et al. 2008). The time envelope for this perception hasalso been reported to peak on the first and second days and to decrease to minor levels after fivedays (Jones 1984, Jones and Richmond 1985, Sinclair et al. 1986, Feinmann et al. 1987, Kvam et al.1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jones and Chan 1992, Scheurer 1996). Further-more, Soltis et al. (1971) found that patient’s proprioceptive and discriminatory ability was reducedfour days after the insertion of orthodontic appliances. The patient’s discomfort at onset and duringvarious stages of treatment was attributed to the lowering of the pain threshold and disruption of thelevel of proprioception of the nerve endings in the periodontal ligament (Jones 1984). It seemedappropriate and was decided to follow the pain experience for three days after each orthodonticprocedure. In this sample, the first day after each procedure was reported to be related to mostdiscomfort, with systematic relief of the pain experience from the first to the third day.Questions regarding the occurrence of pain as response to seven different stimuli were included(Appendix I). The selection of these stimuli is a critical task, since most often and justifiably so; thevariables are chosen to reflect the effects of orthodontic forces on periodontal tissues, such asmastication of food, fitting anterior and posterior teeth together. Included were also functions thatwould provide information to study the possible effects of the orthodontic forces on the dental pulp,such as the responses to cold and hot food/drink. Eating sweets was included to serve as the controlas well as an indicator of possible responses from exposed dentine. Therefore comparing theseselected stimuli seemed logical because there is a difference in the induction of pain responses forexample from, taking sweets, cold food/drink and mastication of food, which can be related toexposed dentin, pulpal and/or periodontal inflammation and hypersensitivity. The most frequentvariables describing pain experience related to orthodontic treatment were mastication of food,fitting anterior and posterior teeth together followed by tooth brushing, cold and hot food or drink,respectively. Eating sweets only seldom induced any pain or discomfort.Responses from the TMJ and soft tissues (lips, cheeks, gingiva and tongue) to orthodontic ap-pliances were not included in the questionnaire. Patients were directed to possibly respond to the 59
  • 58. sensations evoked by orthodontic appliances to the teeth only. Scheurer et al. (1996) have alsoreported that TMJ and soft tissues were not significantly affected by fixed orthodontic appliances,but the discomfort during orthodontic therapy was mainly localized at the teeth.There were no questionnaires given to the patients before the treatment, although it could behypothesized that the discomfort during the orthodontic treatment may be associated with thepreexisting pathologies and malocclusions. This should be taken into account when considering thepain symptoms and discomfort which orthodontic treatment may induce. However, during theprocess of data collection for diagnostic purposes none of the patients included in the studyindicated to have suffered from any dental pain. Moreover, responses to the questionnaire showedconsiderable differences in the pain reports among different stages of treatment.The method used for assessment of the intensity of pain in this study was a numeric rating scale andadopted version of the verbal rating scale (Bond 1979). It has been successfully used in previousstudies (Newman 1980, Jones 1984, Kontturi-Närhi 1993). The method proved to be reliable, andwas considered adequate for the purpose of this study, although, it may pay more attention to theemotional, cognitive and motivational variables that modify the pain or discomfort sensation (Jones1984).Estimating quality of the experienced dental pain has been excluded from the pain research inorthodontics. Evaluating quality of pain symptoms, reflecting also the intensity of pain inhypersensitive dentin proved to be a reliable method and gave valuable information in a study byKontturi-Närhi (1993). Consequently, for the first time in orthodontic literature the present studyincluded systematic evaluation of the quality of pain symptoms induced by different orthodonticprocedures.The descriptors of the type or quality and duration of pain have been used earlier (Addy et al.1987b, Orchardson and Collins 1987a, Kontturi-Närhi 1993). McGill’s Pain Questionnaire MPQ, orverbal checklist were not used in the present study because of the restrictions due to the length andthe laboriousness of the questionnaire, although this method has advantages like it’smultidimensional nature and better ability to express the affective aspects of pain (Gracely et al.1978, Duncan et al. 1989). Even in the MPQ the vocabulary is limited and moreover, it’s use istime-consuming (Gracely et al. 1978). According to Curro (1990) no pain-word questionnaire hassufficient properties for an ideal pain measurement. 60
  • 59. In the studies of pain connected to orthodontic treatment, duration of the pain experience is mostoften referred to and usually measured either in hours or days. In addition to the measurement of thetime envelop of the pain related to orthodontic treatment for three consecutive days, it was found inthis study necessary to also evaluate and assess the duration of such immediate pain symptoms asthey occur. Therefore, patients were requested to respond to the duration (short or long) of theprovoked painful sensation. Although, rather crude, it was chosen to keep the questionnaire simple.A quite similar binary scale for the description of pain duration has been used satisfactorily(Kontturi- Närhi 1993).The need to have numerical values for the statistical analyses lead to study a possible relationshipbetween the intensity, quality and the duration of the experienced pain. Further assessment of theresults revealed the existence of a relationship between the intensity of the different descriptors usedto explain the quality of pain symptoms. The intensity increased from sore to shooting and furtherto dull pain, with ache having the highest intensity. Looking at the association between the intensityand the quality of the pain experienced one might argue that the differences between the intensity ofthe pain descriptors were small and not statistically significant. However, the pain descriptorchanges at different stages of treatment (separation of the first molars, initial archwire insertion andarchwire activation) did not exceed 6.5%, with the average changes being at less than 2% level.Therefore, it could not have affected the results significantly. Long duration pain had reportedlyhigher intensity than short lasting pain. Based on the association between the intensity, quality andduration of pain symptoms an Index (page 26) was formed describing the pain experience. It wasjustified to arrange the descriptors of pain in such a way so that the combination of the intensity,quality and the duration of pain reports would facilitate the use of statistical methods. Thesensitivity and reliability of the Pain Index was confirmed when the results from the prevalence,intensity, quality and the duration of the pain reports were considered separately. Evaluation of theresults as regards to the Pain Index, therefore, should be handled with caution, since they do notrepresent absolute values, rather a combined measure of the intensity, quality and duration of thepain experienced6.2.2. Subjective pain symptoms related to different orthodontic proceduresPrevalence of the pain was highest after the placement of the initial archwire in comparison to theseparation of molars and activation of the archwire. Proportion of patients who experienced painwas 70% after separation of molars, 96% after initial archwire insertion and 69% after archwireactivation. These results are in agreement with the previous investigations, Kvam et al. (1987) re- 61
  • 60. ported that 95% of all patients experienced from fixed orthodontic appliances (initial archwire),Scheurer et al. (1996) also reported the prevalence of pain to be at 94% within the first 24 hours.Similar observations have been made (Wilson et al. 1989, Ngan et al. 1989 and 1994, Jones andChan 1992). The pain experienced after each of the three orthodontic procedures had higher painscore in the first day, which gradually decreased toward the third day. A point worth mentioninghere is that over all, during the initial archwire insertion higher proportion of the subjects had pain -on the second day than on the first day. However, when considering the intensity, quality and theduration of pain, the total score for the pain experienced was higher during the first day.Prevalence of pain experience during the first days after each orthodontic procedure also indicates,statistically significant differences between the first day after the initial archwire insertion (W1) andthe first days after separation of molars (S1) in connection with all items but sweets, also between(W1) and the fist day after the archwire activation (A1) except for sweets and hot food/drink.However, such statistical differences were limited only to fitting teeth together between thearchwire activation (A1) and separation of molars (S1).6.2.3. Intensity, quality and duration of the pain symptomsThe intensity of the reported pain during the study period (all three stages combined) was mostfrequently mild 62.5%, followed by moderate 28.5% and severe pain 9%. However, after theinsertion of initial archwire, which was reported to be the most painful stage of the treatment, thepain reports showed higher intensities, 52.7% being mild, 33.9% moderate and 13.4% severe pain.Pain intensity in the present study cannot be compared directly to the study by Jones (1984).However, in contrast to his conclusions that out of 30 patients, 23 suffered moderate to severediscomfort, in the present study mild pain showed by far the highest proportion among the reports.According to Locker and Grushka (1987), most of the orofacial pain symptoms were reported asmild and that severe or intolerable orofacial pain was found in 11.5% of their subjects. Gradual de-crease of the reported intensity of pain from the first to third day was apparent in the present study -which is in agreement with the previous reports (Jones 1984, Jones and Richmond 1985, Sinclair etal. 1986, Feinmann et al. 1987, Kvam et al. 1987, 1989, Ngan et al. 1989, Wilson et al. 1989, Jonesand Chan 1992, Scheurer 1996). The results of the present study indicate that the pain experiencedduring the initial archwire insertion was the most intense. Also the first day after each orthodontictreatment stage was connected with the highest discomfort, which was generally of mild tomoderate intensity. 62
  • 61. The proportions of different types or qualities of the pain symptoms reported during the studyperiod were 63.5% for sore, 14.3% for shooting, 14.3% for dull and 7.9% for aching pain. The firstday after any of the three orthodontic treatment stages showed the most frequent aching painreports, the highest being on the first day after initial archwire insertion. As mentioned earlier thetype or quality of the pain experience did not change significantly between different orthodonticprocedures and during the insertion of initial archwire the distribution of the quality of pain changedminimally, 65.2% for sore, 14.6% for shooting, 12.1% for dull and 8.1% for ache. The resultssuggest that the type or quality of the pain experienced during orthodontic treatment does notchange significantly.The first day after any of the orthodontic treatment stages had higher frequency of long durationpain among the three days, with the highest recording being during the first day after initialarchwire insertion. An interesting observation is that the occurrence of the long duration of painalso declined gradually from the first to the third day.6.2.4. Analgesic consumptionThe individual variation is reflected in the consumption of analgesics because it could be a matter ofwhether a person preferred avoiding medicine or was keen on taking analgesics on a preventivebasis. Ideally an analgesic drug provides significant relief across all pain severities, has minimalside effects, has few drug interactions and is convenient to administer (Altman 2004, Antman et. al2007, Chang et. al 2005, Savage and Henry 2004, Zelenakas et. al 2004). Although somewhat acoarse method for pain assessment analgesic consumption showed a similar pattern to the responsesfrom the questionnaires. In this sample, regression model showed that after the initial archwireinsertion T2 and archwire activation T4, there was a need for pain medication. At the peak of thereported pain symptoms, during the initial archwire insertion 15 patients, about one in four, reportedthe need for pain medication. However, during the separation of molars and wire activation thecorresponding number was only two. At the initial archwire insertion stage about one fourth ofpatients reported taking medication with one patient taking three doses during the first day. Thedemand for analgesics was limited to the first and second day during the separation of molars andactivation stage with no patient reporting having taken medication on the third day. However,during the initial archwire insertion 5% of patients took medication for pain relief on the third day,this is in agreement with the results from Jones (1984) and Scheurer et al. (1996). In contrast to thefindings of Feinmann et al. (1987) who reported no correlation between the pain experience andanalgesic consumption, in the present study a correlation was found between the total pain score 63
  • 62. and the use of analgesics.Ngan et al (1994) have reported that after one initial dose of analgesics at the moment of orthodon-tic appliance insertion, none of the patients needed additional pain relief. Although in the presentstudy neither prescription for pain medication nor analgesics were dispensed to the patients, it ispossible that some patients consumed the analgesics as a preventive measure.First and second days after either initial archwire insertion or archwire activation, provoked theexperienced pain and the need for analgesic.6.2.5. Dental pain sitesPain connected to orthodontic tooth movement most probably originates from the periodontaltissues due to mechanical injury and consequent inflammatory reaction. However, also intradentalnociceptive nerves may be involved because periodontal inflammatory reactions may spread to thepulp due to formation and diffusion of various inflammatory mediators, and neurogenicinflammation mediated by branching axons, which are known to innervate both the pulp andperiodontal ligament (Byers 1984, 1985, 1994, Byers et al. 1992b). Moreover, as alreadymentioned, nerve sprouting also takes place within the pulp in response to orthodontic forces, whichmay affect the functional properties of the intradental nerves. Also, possible impairment of thepulpal blood flow due to vessel compression may play a role.Chewing something fairly hard -a plastic wafer, for example- within the first two hours after archwire adjustment may act to reduce the ischemia and inflammation in the periodontal ligament(Furstman and Bernick 1972). Stimulation of vascular and lymphatic circulation would prevent thebuild-up of metabolic products, which are known to stimulate pain receptors (Proffit 1986).The pain experienced during separation of the first molars understandably was related to themastication of food and fitting posterior teeth together. Interestingly fitting anterior teeth togetheralthough not at a statistically significant level, was also affected to some extent with the placementof orthodontic separators. Similar observations have been made by Ngan et al. (1989).At the initial archwire insertion the responses were mostly concentrated in mastication, as well asfitting anterior and posterior teeth together respectively. This is not surprising since insertion of thearchwire for initial alignment tends to increase the level of discomfort on the front teeth. This 64
  • 63. finding is in agreement with previous studies (Ngan et al. 1989, Scheurer et al. 1996) and furtherdemonstrates the sensitivity of the questionnaire used in the present study.A month later at the activation of archwire, however, the responses were different, fitting anteriorteeth was the most frequently recorded function inducing pain, followed by mastication of food. Atthis stage the experienced pain caused by fitting posterior teeth together was at its lowest level,which may suggest that as the orthodontic treatment progresses, at least during the initial stage,there is a gradual decrease of the pain symptoms which seems to start from the posterior teeth.6.2.6. Relationships between the pain symptoms during initial tooth movementand age, gender, and treatment approach.Over the years the question of whether or not age has an influence on perceived pain duringorthodontic therapy has remained controversial, partially due to the differences in study designs andexperiments. In this study, the clinical data indicates a higher discomfort experience in patients aged16 and over than those of under, being at a statistically significant level in connection with incisors,canines and premolars during activation of the archwire in response to cold stimulation at 15ºC.This is in agreement with the findings of Jones (1984), Jones and Chan (1992).It has been suggested previously that pain might be related to gender (Feinmann et al. 1987).However, in the present study no statistically significant difference was found between genders inthe subsequent pain responses. Earlier reports seem to agree with this finding (Jones 1984, Ngan etal. 1989, Jones and Chan 1992). However, Kvam et al. (1987), and Scheurer et al (1996), haveobserved that females reported a higher impact on daily life from orthodontic appliances thanmales.Pain symptoms did not differ between extraction and non-extraction cases. Some orthodontists mayprefer to initiate the treatment of one arch at a time to alleviate the pain. Except for molarsresponses to cold stimulation at 15ºC during the archwire activation indicating less sensitivity whentreating one arch, the results from this study did not indicate that this treatment strategy wouldreduce the perceived pain/discomfort. This finding is in line with the findings of Scheurer et al.(1996), and Jones and Chan (1992). 65
  • 64. 6.3. Clinical study6.3.1. Electrical tooth stimulationElectrical pulp testing methods were first developed in the 1860´s and since that time, manydifferent methods have been used (Lin and Chandler 2008), dealing with faradic current, galvaniccurrent, direct, alternating, or high frequency alternating current (Burnside et al. 1974). Electricalstimulation is convenient in that the stimulus intensity needed to evoke a sensory response can bedetermined accurately. The end point of electrical stimulus determination is a threshold sensation,prepain. Mumford (1973) stated, "Electrical stimuli are at once the most natural and the most artifi-cial of the stimuli applied to the teeth. They are natural in that conduction through the tissues iselectrolytic, depending on ionic movement, and ionic movement is fundamental to nerve excitation.They are artificial in that electrical stimuli not applied to the teeth in the natural way that thermalstimuli are when eating and drinking. However, electrical stimuli have the great advantage overother stimuli that they can be precisely defined by electronic methods."Constant current stimulator used in the present study had optimal output characteristics with 10 mscathodal square wave pulses (Björn 1946, Mumford and Björn 1962, Mumford 1982). Matthewsand Searle (1974) have investigated seven different pulp testers and reported Bofors® pulp tester(the electrical stimulator used in the present study) to be the most reliable. Constant currentstimulator minimizes the effect of possible variations in the impedance of the stimulation circuit(Mumford 1982). If the stimulation were not of constant current type, any changes in the impedanceof stimulation circuit would result in a change in the effective (stimulating) current intensity in thepulp (Kontturi-Närhi 1993). The current density in the area of the nerve fibers is decisive for theiractivation (Mumford 1982). Thus, measurement of voltage in the teeth is unsatisfactory, voltagedrop may vary because of variations in electrical resistance of the dental hard tissues. In addition,cracks, pits, fissures, caries, restorations, and fractures may cause variations in electrical resistance.Therefore, in order to overcome such variations in resistance, a stimulator that measures currentrather than voltage should be used.During the stimulation of teeth the electrode was in contact to the incisal/occlusal third on thelingual surface of the teeth, cervical stimulation was avoided because of the possibility of currentleakage to the soft tissues with the low resistance (Mumford and Björn 1962, Matthews and Searle1974, Mumford 1982). The lingual surfaces were used for electrical stimulation to avoid possibleinterferences from the brackets. In the view of the fact that all efforts on the part of examiner weremade to isolate the teeth from saliva and tongue, there were cases especially in the lower jaw that 66
  • 65. made this task difficult. Saliva would provide a current leakage to the soft tissues thereforeincreasing the readings significantly. Thus each tooth was tested twice at any given session and ifthe difference between the two recordings more than 10 µA for incisors, more than 15 µA forcanines and premolars and more than 25 µA for molars the lower value was taken for statisticalanalysis instead of taking a mean value.Teeth which were not fully erupted were excluded from the clinical testing, because the larger thequantity of pulp tissue the smaller is the electrical impedance, the amount of electrical currentpassing through a unit area in the pulp is greatest where the pulp tissue is thinnest (Hargreaves1973). There was no statistically significant differences between the maxillary and mandibulardental electrical thresholds, thus they were combined. Teeth were further grouped as recommendedby Mumford (1982) in the following order, 1) incisors, 2) canines and premolars and 3) molars.Nordh (1955) used the Björn pulp tester for testing 36 teeth on the same day before and after orth-odontic band placement and reported no significant difference in the perception thresholds. He alsotested 13 teeth (with a control group of 10) before and after orthodontic space closure and found nosignificant differences. Burnside et al. (1974) reported higher pain threshold values to electricalstimulation in the experimental group, however the comparison was made between patients whohad fixed orthodontic appliances for a minimum of four months prior to testing and a control groupwithout any appliances.Effectiveness of an electrical current in stimulating a tooth does not depend on the presence ofreceptors at the pulp dentin junction, this activation likely occurs on more central component of theaxons in dental pulp (Mumford 1982, Närhi 1985b). Mumford (1982) has further reported teethwith hyperemia or acute pulpitis not to have a lower electrical threshold. Therefore, the electricalthreshold determination does not give much if any information on the receptor sensitivity. Kontturi-Närhi (1993) has also reported similar findings. Because of the longitudinal nature of this study andtooth responses to orthodontic forces and pulpal tissue reaction to such forces (i.e. hyperemia), aninteresting objective of the present study was to find out if there were any changes in electricalthresholds of the teeth. However, the results have clearly demonstrated that dental electrical thresh-olds were generally constant, before, during and after different orthodontic treatment procedures. 67
  • 66. 6.3.2. Cold sensitivity testsCold has been reported to be the most potent irritant in inducing pain in hypersensitive teeth(Naylor 1961, Brännström 1981, Dowel et al. 1985, Flynn et al. 1985, Närhi 1985a, Orchardson andCollins 1987a,b, Kontturi-Närhi 1993). Extreme cold for pulp vitality test has long been in use.Saxer (1958) using dry ice or carbon dioxide snow for pulp vitality test, reported in 1000 teeth anaccuracy of 97.5%, compared to 97.2% for electrical pulp testing. Although the temperature ofcarbon dioxide snow is -78ºC, Augsburger and Peters (1981) found that the intra pulpal tempera-ture, as measured in vitro, decreased only by a mean value of 15.6ºC for non-carious teeth. Theirclinical studies indicated that a 2-second exposure was sufficient to produce a sensory response.The present study is the first in the orthodontic literature to have extensively investigated pulpalreaction to orthodontic tooth movement. Additionally, it is the first to use an accurate and reliableelectrothermal device for evaluation of the intensity of orthodontic related pain symptoms.The electorthermal device used in the present study for the cold stimulation was constructed at theTechnical Center of the University of Kuopio, Finland. The reliability of a similar device has beenconfirmed previously and cold stimulation was found to be the most suitable for dentin sensitivitytests (Kontturi-Närhi 1993). The desired temperature could be adjusted with an accuracy of 0.1ºC,which is more than satisfactory for the clinical tests. The size of the stimulator tip was suitablehaving a sufficient thermal capacity and allowing a good access to the teeth. The thermalstimulator’s tip was flat, the contact area varied considering the shape of the tooth surface. Thismay have caused variations in the stimulus applied. However, this variation was acceptable becauseof the good correlation between the responses to cold stimulation at the different temperaturesstudied.Visual Analogue Scale (VAS) was used to evaluate the intensity of the induced pain during the coldstimulations. This method is widely used for measuring pain and has been described by otherinvestigators as being sensitive and reliable and also having certain advantages over verbal scales(Uskisson 1974, Huskisson 1983, Seymour et al. 1985, McGrath 1986, Duncan et al. 1989). VAS isa direct rating scale and offers a continuum of different pain intensity levels (Huskisson 1983) andaccordingly allows the use of parametric statistical tests (Bhat 1986).Cold stimulation at 0ºC induced more pain than at 15ºC before, during and after application oforthodontic forces during the study. The pain responses to clinical examinations at 0ºC and 15ºC, 68
  • 67. interestingly, were corresponding to the fluctuation of the pain experience as reported by thepatients in response to the questionnaire. Also the subjective pain reports indicated the initialarchwire insertion to be the most painful stage of treatment. The cold responses were the mostintense in incisors, canines/premolars and molars respectively. The incisors which were the mostsensitive tooth group to cold showed the most intense pain responses during initial archwire inser-tion which is in agreement with the questionnaire results.Although, the proportion of teeth responding to cold stimulation at 15ºC was significantly lowerthan at 0ºC, by no means this test is less effective in its ability to distinguish between differentstages of treatment. Using paired t-test revealed that responses of the first molars to cold stimulation at0ºC, also incisors, canines and premolars at 15ºC were at a statistically significant level whencomparing the initial archwire insertion to other stages of the orthodontic treatment.An interesting observation was that when considering cold stimulation at 0ºC only molars werefound to be responding at a statistically significant level. However, during cold stimulation at 15ºCsuch differences were exclusive for incisors, canines and premolars. One explanation for thedifferences could be that two seconds of cold stimulation at 15ºC for molars was not sufficient forthe differentiation of responses considering the thickness of the enamel and dentin of such teeth. Onthe other hand cold stimulation at 0ºC was able to differentiate the most sensitive stage (initialarchwire insertion) from all other stages. Looking at the responses from incisors, canines andpremolars, it seems that cold stimulation at 0ºC although evoked more responses overall (28.2%-34.6%) than 15ºC (6.25%-11.7%), it might have been too strong a stimulus for patients’discriminatory ability to differentiate among different stages of the treatment. However, cold stimu-lation of incisors, canines and premolars, at 15ºC was able to differentiate the sensitivity changesduring different procedures of orthodontic therapy.Although the changes in the dental cold sensitivity during orthodontic treatment were small theyindicate that part of the discomfort and pain experienced by the patients may, in fact, be of pulpalorigin. It has been shown that morphological changes in the pulpal innervations can be induced byorthodontic forces (Yamaguchi and Kasai 2005). The sensitivity changes found in the present studymay be related to such morphological nerve responses. 69
  • 68. 6.3.3. Comparison of different fixed orthodontic appliancesBoth techniques under trial in this study used light continuous forces. Aside from the obviousdifferences in the bracket designs, there are two major differences between the two approaches.First, the dimension and the amount of the force delivered by different initial archwires and second,the use of closed coils in extraction cases.Using the Irregularity Index there was no statistically significant difference between the two fixedappliance groups prior to orthodontic treatment.The decisions for extraction of teeth were made either to relieve the severely crowded dental archesand/or to reduce the excessive over jet and/or over bite. Although, all extraction spaces werecompletely closed by the end of the orthodontic treatment, the study period considers only the toothmovements, which occurred during the first three months of the treatment, and compared the toothmovements accordingly.One difference was the timing of the application of force, for canine retraction in extraction cases.Because, as shown by Quinn and Yoshikawa (1985), once the force threshold for tooth movement isreached, the magnitude of the force applied to the teeth becomes less important. Therefore, usinglight forces to have a control of the unwanted movement of the anchor teeth is a fact, which wastaken into account and in the sample studied. Although not separately studied, clinically there wasno evidence of anchorage loss.Generally, the results of the present questionnaire study indicated no statistically significantdifferences in terms of the pain experienced, in either of the initial archwires or their activationstages between the two techniques. Patients inability to distinguish between the two lightcontinuous force systems used in the study, is in line with the previous findings (Boester andJohnston 1974, Andreasen and Zwanziger 1980, Jones and Richmond 1985, Jones and Chan 1992,Scott et al. 2008). Using the Irregularity Index (Little, 1975) for evaluating the anterior crowdingrevealed no statistically significant difference between the two techniques. This finding is alsosupported by the conclusion of O´Brien et al. (1990). In extraction cases using closed coils at theinitial stage increased tooth movement was observed during the period of three months. It is a factthat at present no archwire is "ideal" for all type of orthodontic tooth movement. This is notsurprising because the demands of the treatment plan require different characteristic stiffnesses andranges (Kusy 1997). 70
  • 69. Results from the thermal sensitivity tests using Visual Analogue Scale (VAS) have indicated thatthe differences between the groups were altogether small and do not as such justify too extensivecomparison of the two techniques.Ideally the orthodontic forces should be kept to a level below the pain threshold of each individualpatient. Our results indicate that slight difference in the forces applied, assuming it is within therecommended range, type and duration, during the initial phase of the orthodontic treatment is notdirectly related to the pain experienced by the patients and the tooth sensitivity. Obviously, there isa difference in the timing of the force application in extraction cases between the two techniques,and the picture becomes more complicated when we consider the type of tooth movement, forexample, tipping and rotation. Further study is necessary to answer these questions. In light of thepresent results it is therefore recommended that the bracket design and ligation system should bemodified in such a way that can accommodate and take advantage of the ever changing newinformation and wire technology. 71
  • 70. 7. SUMMARY AND CONCLUSIONSThe present study was performed to assess the experienced pain as reported by the patients atdifferent stages of orthodontic treatment. It was also examined if orthodontic forces and toothmovement affect the dental pulp sensitivity, and if such sensitivity is related to the pain experience.The study subjects were 64 orthodontic patients, 46 females and 18 males, with the mean age of26.4 (SD 11.2) years and range of 10.8-49.3 years. The sample consisted of consecutive cases ofpatients who were willing to participate in the study. A structured questionnaire was used to mapthe prevalence, intensity, quality and duration of pain/discomfort after separation of first molars,after the initial archwire insertion and after the first activation of the archwire, for three days aftereach stage. Dental electrical thresholds were measured using an electrical pulp tester and thermalsensitivity measurement was carried out with an electrothermal device at 15ºC and 0ºC. Theintensity of the pain induced by cold stimulation was assessed using a 100 mm Visual AnalogueScale (VAS). Deciduous teeth were excluded from the clinical measurements. Altogether 907permanent teeth of 64 patients were measured at all stages of the study. Tooth movement (mm) wasmeasured from the hard stone casts using the Irregularity Index (Little 1975). Additionally, twodifferent orthodontic techniques, namely those of the Alexander and the Viazis, were compared forthe pain experienced, dental sensitivity to cold stimulation and electrical thresholds as well as forthe rate of the tooth movement.The prevalence of the pain reports according to the questionnaire was higher after the initialarchwire insertion (96%) than after the separation of the first molars (70%) or the archwireactivation (69%). The first day after any of the three orthodontic treatment stages had the mostfrequent pain experience, the highest being on the first day after initial archwire insertion. The mostcommon stimuli related to pain during the first three days after the initial archwire insertion were:1) mastication of food in 90.2% of the subjects 2) fitting anterior teeth together in 82.7% 3) fittingposterior teeth together in 78.6% 4) tooth brushing in 47.6% 5) cold food/drink in 27.4% 6) hotfood/drink in 22.3% and 7) sweets in 9.8%. Longer duration of the experienced pain was reportedduring the first day after any of the orthodontic procedures, the highest being recorded during thefirst day after the initial archwire insertion. The perceived pain decreased significantly from the firstto the second and further to the third day after each orthodontic procedure.The intensity of the reported pain during the study period was most often mild, in 62.5% of thereports followed by moderate pain in 28.5% and severe pain in 9%. The pain reported by thepatients after different orthodontic procedures was most often described as sore (63.5%), followed 72
  • 71. by shooting (14.3%), dull (14.3%) and aching (7.9%) pain. Generally, the quality or type of the painsymptoms remained constant during the initial stage of orthodontic treatment. The duration of thepain symptoms reported after different orthodontic procedures was usually short, in 85% of thereports, compared to long duration found in 15%.The analgesic consumption showed a similar pattern as the prevalence and intensity of the painreports. In general, patients who consumed analgesics reported more pain symptoms.There were no statistically significant differences between the reported pain and gender, extractionversus none extraction, type of fixed appliance, or treatment of one or both arches. Although, not ata statistically significant level, the data indicates a higher discomfort experience in patients aged 16and over, compared to the younger subjects.The lack of changes in response to dental electrical stimulation during the study period may suggesta poor relationship between the dental electrical threshold and the possible changes in the dentalpulp after the application of orthodontic forces. However, It is also possible that the extent of whichthe dental pulp is affected by the orthodontic forces is simply not enough to change its electricalthresholds.The proportion of teeth responding to the cold stimulation at 0ºC was higher than at 15ºC, and thepain ratings measured using the Visual Analogue Scale were significantly higher for 0ºC. Coldstimulations at 0ºC and 15ºC, interestingly, correspond to the results from the questionnaire,indicating the pain experienced after the initial archwire stage to be the most intense. It wasdemonstrated that there is a change in cold sensitivity of the dental pulp subsequent to orthodontictreatment and that such sensitivity is highest after the initial archwire insertion.Cold stimulation at 0ºC and 15ºC induced pain (all tooth groups combined) in 28.6% and 6.2%before the treatment, 34.6% and 11.7% three days after the initial archwire insertion followed by30.9% and 6.9% before the archwire activation stage, and 28.2% and 9.5% three days afteractivation, respectively. Incisors were the most sensitive group of teeth, showing the most frequentresponse 47.7%, the highest pain scores at 0ºC three days after the initial archwire insertion, whichis in agreement with the questionnaire results. The differences of the first molars VAS scores tocold stimulation at 0ºC were at a statistically significant level when comparing initial archwireinsertion stage to: initial (p=.024), separation of molars (p=.013), activation (p=.019) and three daysafter activation (p=.017), stages. The differences in the incisors responses to cold at 0ºC between 73
  • 72. initial stage and initial archwire stage, (p=.079) showed a tendency to increase in sensitivity,although, not at a significant level. Statistically significant differences at 15ºC (paired t-test) werefound between the initial stage and the initial archwire insertion in, incisors (p=.042), canines +premolars (p=.026), between initial archwire and activation stage in, canines + premolars (p=.002),between activation and three days after activation in, canines + premolars (p=.036). The incisorsresponses between the initial archwire and the activation stage followed the same pattern, although,the difference was not statistically significant (p=.065).In general the differences in the prevalence of pain between the two different fixed appliances weresmall and statistically significant only in connection with some of the questionnaire items, whichaltogether gave the most frequent pain reports. Such items were mastication, as well as fittinganterior and posterior teeth together. Results from the thermal sensitivity tests using VisualAnalogue Scale (VAS) have indicated that the differences between the groups were altogether smalland do not as such justify too extensive comparison of the two techniques.Comparing orthodontic tooth movements with different fixed appliances, using the irregularity in-dex (Little 1975) for the maxillary and mandibular anterior crowdings (canine to canine) showed nostatistically significant difference between the two fixed orthodontic appliances. In extraction cases,increased orthodontic tooth movement was observed using the closed coils. 74
  • 73. On the basis of the present study, the following conclusions can be drawn:Orthodontic treatment generally induces pain and discomfort, which could mostly be categorized asmild and short lasting. However, some patients do experience severe pain during the treatment evento the extent that, mastication of food and tooth brushing might be impaired.Pain is experienced after orthodontic procedures at different stages of treatment. Analgesicconsumption is correlated with the intensity of the pain experienced. Depending on the patients painthreshold, clinicians should consider prescribing pain medication to alleviate the unpleasantexperience.The pain experienced during orthodontic treatment originates mostly from periodontium, due tomechanical injury and consequent inflammatory reaction. Pulpal changes do not seem to contributesignificantly to the patient`s overall pain experience. However, sensitivity of teeth to coldstimulation during the treatment correlates to the pain responses from the questionnaire study,suggesting that responses in the dental pulp also play a role. No correlation was found between theelectrical stimulation of teeth and the pain responses from the questionnaire study.Inability of patients to distinguish between different light continuous forces during the initial phaseof the orthodontic treatment was observed. Neither the pain experienced by patients nor the toothsensitivity was affected by different archwires used in the present study. Amount of toothmovement, during the initial phase of the orthodontic treatment does not seem to be directly relatedto the pain symptoms experienced by the patients. 75
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  • 92. APPENDIX IThe questionnaire used in the present study. Stimulus Sore Shooting Dull Ache Sweets 0 Duration 0 Duration 0 Duration 0 Duration 1 S 1 S 1 S 1 S 2 L 2 L 2 L 2 L 3 3 3 3 Hot, 0 0 0 0 1 S 1 S 1 S 1 S Food/Drink 2 L 2 L 2 L 2 L 3 3 3 3 Cold, 0 0 0 0 1 S 1 S 1 S 1 S Food/Drink 2 L 2 L 2 L 2 L 3 3 3 3 Tooth brushing 0 0 0 0 1 S 1 S 1 S 1 S 2 L 2 L 2 L 2 L 3 3 3 3 Mastication of 0 0 0 0 1 S 1 S 1 S 1 S Food 2 L 2 L 2 L 2 L 3 3 3 3 Fitting anterior 0 0 0 0 1 S 1 S 1 S 1 S teeth together 2 L 2 L 2 L 2 L 3 3 3 3 Fitting posterior 0 0 0 0 1 S 1 S 1 S 1 S Teeth together 2 L 2 L 2 L 2 L 3 3 3 3 94
  • 93. APPENDIX IIAssociations between the subjective pain reports and clinical measurementsAssessment of the possible associations between the subjective pain reports (the questionnairestudy), and clinical measurements (cold tests 15/0ºC and electrical vitality tests µA), wasfurther studied.Multiple regression analyses were used to estimate the associations between the painexperienced at different stages of orthodontic treatment (Index 3, 0-504) namely afterseparation of the first molars, after initial archwire insertion and after initial archwire activationand cold sensitivity tests at 15ºC and 0ºC (mean VAS values, 0-100 mm), electrical vitalitytests (mean, 0-125 µA), in different tooth groups (1.Incisors, 2. Canines and Premolars, 3.Molars), considering the effects of age (1<16, 2≥ 16 years), gender (0=female, 1=male),extraction of teeth (0=no, 1=yes), fixed appliances used for orthodontic treatment (1=Alexander, 2=Viazis), analgesic consumption (0=no, 1=yes), one or both jaws treatment(1=maxillary or mandibular, 2=both jaws). Due to high correlation between different toothgroups in cold and electrical measurements, as well as, cold measurements between 15ºC and0ºC, separate regression models were prepared. There were no statistically significantdifferences between the pain experienced after separation of molars and the independentvariables (Table.14).Medication for the management of pain during the first three days after the initial archwireinsertion and the archwire activation was statistically significant in the tooth groups in both ofthe models. Pain experienced by patients aged 16 years and over after archwire activation stagein both incisors, canines and premolars tooth groups, in model A, was statistically significant.Statistically significant associations were found in relation to all the tooth groups after theactivation of archwire and molars after the initial archwire insertion and cold measurements.Treatment of both jaws in response to molars was statistically significantly associated with themodel A. 95
  • 94. Association between the reported pain after the insertion of initial archwire stage, activation ofarchwire stage, and independent variables. Cold and electrical measurements are from differenttooth groups; 1) central and lateral incisors, 2) canines and premolars, 3) molars. (Coldmeasurements at 15ºC in Model A and at 0ºC in Model B). Only statistically significantdifferences are given.Tooth groups Treatment stage/ Model A Model B Independent variables Regr. coeff. P Regr. coeff. P Incisors After initial archwire/ Analgesic consumption 49.8 .008 49.8 .008 After archwire activation/ Age 1.5 .045 Analgesic consumption 103.9 .004 76.9 .019 Cold VAS (mm) 2.2 .043 1.3 .003Canines/premolars After initial archwire/ Analgesic consumption 49.8 .008 49.8 .008 After archwire activation/ Age 1.4 .049 Analgesic consumption 110.6 .002 101.9 .002 Cold VAS (mm) 7.8 .018 3.1 .001Molars After initial archwire/ Analgesic consumption 45.3 .015 54.7 .007 Cold VAS (mm) 5.5 .019 After archwire activation/ Treatment of one or both jaws 40.5 .008 Analgesic consumption 67.6 .037 104.7 .000 Cold VAS (mm) 2.8 .000 96
  • 95. APPENDIX III The mean values of VAS pain ratings to 15ºC cold stimulation at different stages of the orthodontic treatment are presented. Incisors were the most sensitive during the trial period followed closely by canines, premolars and molars. No significant statistical differences were found between maxillary and mandibular teeth responses at different stages of the treatment using the paired t-test. molars. Statistically significant differences (paired t-test) were found between initial stage and initial archwire stage in, incisors (p=.042), canines + premolars (p=.026), between initial archwire and activation stage in, canines + premolars (p=.002), between activation and three days after activation in, canines + premolars (p=.036). Although, not statistically significant (p=.065), the incisors responses between the initial archwire and the activation stage followed the same pattern. mm25 6 5 4 3 2 1 0 maxilla mandible25 I II III IV V The mean VAS pain ratings to 15ºC cold stimulation at different stages of the orthodontic treatment (I = initial, II = separation of molars, III = three days after the initial archwire insertion, IV = before wire activation and V = three days after activation) in maxillary and mandibular teeth (1 = incisors, 2 = laterals, 3 = canines, 4 = first premolars, 5 = second premolars and 6 = molars). 97
  • 96. APPENDIX IV The mean values from VAS pain ratings to 0ºC at different stages of the treatment are presented. The VAS pain ratings to cold at 0ºC were higher compare to 15ºC at all the stages of treatment. Maxillary molars showed a higher VAS ratings than mandibular molars at all the stages being at a statistically significant level, also mandibular central incisors had VAS ratings higher than maxillary central incisors at the activation stage (p<.05). Paired t-test revealed that the difference in the molars responses to cold stimulation (0ºC) were at a statistically signifi- cant level when comparing initial archwire insertion to: initial stage (p=.024), separation stage (p=.013), activation stage (p=.019) and three days after activation (p=.017). The incisors responses to cold at 0ºC between initial stage and initial archwire stage, also showed a substantial increase in the sensitivity, although the difference was not significant (p=.079). mm25 6 5 4 3 2 1 0 maxilla mandible25 I II III IV V The mean VAS pain ratings to 0ºC cold stimulation at different stages of the orthodontic treatment (I = initial, II = separation of molars, III = three days after the initial archwire insertion, IV = before wire activation and V = three days after activation) in maxillary and mandibular teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first premolars, 5 = second premolars and 6 = molars). 98
  • 97. APPENDIX V The dental electrical thresholds at different stages of the treatment are shown. The mean electrical threshold values at the initial measurement in µA for the maxillary arch, were 28.7 in molars, 20.5 in second premolars, 18.5 in first premolars, 14.5 in canines, 12.3 in lateral in- cisors, 11.9 in central incisors, and for the mandibular arch 29.3 in molars, 22.7 in second premolars, 23.1 first premolars, 19.2 canines, 14.9 in lateral incisors, 15.2 in central incisors. The differences in the mean thresholds between the maxillary and mandibular teeth were not statistically significant. Therefore the combined mean electrical threshold values from the maxillary and mandibular teeth were used for further statistical analysis. As with the cold responses the results of electrical stimulation were studied with respect to different tooth groups (1= incisors, 2= premolars and canines, 3= molars). µA30 6 5 4 3 2 1 maxilla 0 mandible30 I II III IV V The mean electrical thresholds of teeth at different stages of orthodontic treatment (I = initial, II = three days after the separation of the first molars, III = three days after the initial archwire insertion, IV = before wire activation and V = three days after activation) in maxillary and mandibular permanent teeth (1 = central incisors, 2 = lateral incisors, 3 = canines, 4 = first premolars, 5 = second premolars and 6 = first molars). 99
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