Retention and relapse /certified fixed orthodontic courses by Indian dental academy

Uploaded on

The Indian Dental Academy is the Leader in continuing dental education , training dentists in all aspects of dentistry and offering a wide range of dental certified courses in different formats.

Indian dental academy provides dental crown & Bridge,rotary endodontics,fixed orthodontics,
Dental implants courses.for details pls visit ,or call

More in: Education
  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
    Be the first to comment
No Downloads


Total Views
On Slideshare
From Embeds
Number of Embeds



Embeds 0

No embeds

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

    No notes for slide


  • 1. RETENTION & INDIAN DENTAL ACADEMY Leader in continuing dental education
  • 2. RETENTION The phase following active orthodontic treatment aimed at stabilization of achieved orthodontic correction or holding of the teeth in ideal functional esthetic occlusion. The holding of the teeth in ideal esthetic and functional position
  • 3. Angle summarized orthodontic retention as follows: "After malposed teeth have been moved into the desired position they must be mechanically supported until all the tissues involved in their support and maintenance in their new positions shall have become thoroughly modified, both in structure and in function, to meet the new requirements."
  • 4. Orthodontics dates back to the very first century when Roman writers Pliny and Galen, who were the founder of experimental medicine, both recommended filing of a tooth that projected from trauma and other reasons. Knowledge about stability of treatment was finally put forth by Emerson C. Angell (1860), as a byproduct of his palate-splitting procedure. He mentioned the necessity to preserve or retain space to until complete eruption and development of the teeth in question.
  • 5. Alfred Coleman (1865) wrote about restoration of various conditions by muscular pressure— in other words, the first allusion to relapse. More than a century later, clinicians still refer to abnormal muscular pressure as a dominant factor in the cause of relapse. Brown-Mason (1872) (in England) described a retaining plate for surgically rotated teeth. Thus, after more than 19 centuries of mechanical orthodontic intervention, recognition of the possible instability of treatment emerged, and thus the concept of a retaining appliance was born.
  • 6. One of the earliest retaining appliances was described by James W. Smith (1881). It was a simple vulcanite plate with a bar extending over the labial aspect of the maxillary incisor teeth. Jackson (1904) suggested that ''after they have been rotated as far as desired, the soft tissue be separated from the neck of the tooth and allowed to reunite in the new location, depending on the cicatrix thus formed to prevent their retrograde movement— in short fiberotomy.
  • 7. Finally, Angle devised and described many ingenious mechanical combinations of cemented bands and spurs, the action of which were, to quote his descriptive phrase, "to antagonize the movement of teeth only in the direction of their tendencies." Also in his quest for the ultimate retainers, it is interesting to note that Angle's intricate pin and tube active treatment appliance was developed primarily as a working retainer to achieve bodily movement or uprighting of teeth that had been tipped outward in expansion.
  • 8. W. S. Bonwill's work (1887) described an ideal morphologic arrangement of teeth and jaws based on his study of more than 2000 skulls. He thoroughly informed his patients of the limits of treatment and the necessity of adequate retention. Also, Bonwill advised the orthodontists to set fees high enough to "insure their own interest and drive the parties concerned up to their duties.“
  • 9.  SCHOOL OF THOUGHTS The Occlusion School 1880 by Kingsley stated that the occlusion of teeth is the most potent factor in determining the stability of the new position. The apical base school 1920 by Alex Lundstrom suggested that apical base is the most important factor in the correction of malocclusion and maintenance of correct occlusion.
  • 10. The mandibular incisor school by Grieve and Tweed in 1952 suggested that the mandibular incisors must be kept upright and over the basal bone. The musculature school 1922 suggested that the proper functional muscle balance was necessary for maintenance of stability
  • 11. Basic theorems Theorem 1: Teeth that have been moved tend to return to their former positions. This tendency is due to musculature, apical base transseptal fibers, bone morphology. Theorem 2: Elimination of cause of malocclusion will prevent recurrence. Habits such as thumb/finger sucking/lip biting are easy to diagnose as being the cause of malocclusion and can be easily negated to prevent recurrence. The most causative factor as tongue posture can influence and cause anterior/lateral open bite.Tongue posture can be due to open bite secondary to mouth breathing/nasopharynx obstruction which in turn can be due to anatomic blockage, allergic disease or adenoid hyperplasia.Dentofacial changes due to functional alternation appear to become more severe with age.
  • 12. Theorem 3 Malocclusion should be overcorrected as a safety factor” In Class II malocclusion it is in practice to get it into edge to edge incisor relationship by overcoming muscle force rather than by tooth movement only. Over correction of deep bite is an accepted practice. Over rotation to prevent relapse of rotation is not successful as evidence suggests but, is possible by supracrestal fiberotomy.
  • 13. Theorem 4  “Proper occlusion is a potent factor to hold the teeth in that position” Overfunction or Pounding (exerting pressure) of the mandibular canine by maxillary canine is very often blamed for anterior teeth crowding.  However, evidence suggests tremendous wear , that the teeth undergo indicates that they do not move in response to regular grinding and tapping.  Studies indicate that mandibular arches are not stable in both anterior tooth contact and open bite patients without canine contact in centric position and functional excursion. Thus this theory is doubtful.  This again does not mean that proper intercuspation or interlocking of the canine is the most potent factor in retention.
  • 14. Theorem 5 “Bone and adjacent tissues must be allowed time to reorganize around newly positioned teeth”. Histologic studies have shown that the bone and tissue around the teeth, that have been moved, require considerable amount of time before complete remineralization occurs. Some authors believe that retainers should be fixed and others feel that the retainers should be only inhibitory in nature with no the fixation to allow natural functioning of teeth.
  • 15. Theorem 6 “If the lower incisors are placed upright over the basal bone, they are more likely to remain in good alignment”. But no satisfactory method exists for anyone to specify the beginning or end of basal bone. In case of anterior teeth with buccal inclination; attempts to push them lingually causes expansion or collapse in canine area. If anterior teeth are already inclined lingually further pressure to the lingual won’t cause collapse. So if the clinician must make an error in in positioning of the mandibular incisor, it is better to err in the lingual direction rather than a labial inclination.
  • 16. Theorem 7 “Corrections carried out during periods of growth are less likely to relapse”. Hence treatment should begin at the earliest possible age. Correction of disto-occlusion and maintaining the corrected position is difficult without extraction. Advantages of early treatment 1. Prevents progressive irreversible tissue and bony changes. 2. Maximize use of growth and development. 3. Allows interception of malocclusion before excess dental and morphological compensations. 4. Allows correction of skeletal malrelationships while sutures are morphological immature and more amenable to alterations.
  • 17. Theorem 8 “The further the teeth have moved the less the likelihood of relapse”. There is little evidence to support this and the opposite of this statement may be true.
  • 18. Theorem 9 “Arch form particularly the mandibular arch cannot be permanently altered by appliance therapy”. Therefore treatment should be directed towards maintaining them. Dallas McCanley have suggested that canine width and the bimolar width are of such uncompromising nature that they should be considered as fixed quantities and build the arches around them.
  • 19. Theorem 10 “Many malocclusion requires permanent retaining device model”.
  • 20. Biologic Basis for Orthodontic Relapse According to Angle, orthodontic correction will remain stable if the teeth are aligned into a normal occlusion and provided with adequate retention. Orthodontic relapse includes crowding or spacing of teeth, return to increased overbite and overjet and instability of class II and class III corrections. Relapse is defined as “return towards pre-treatment conditions”.
  • 21. Tissue Response in Periodontium If orthodontic tooth movement is not followed by remodeling of supporting tissues, the tooth will tend to relapse. The periodontal ligament has the ability to invest its fibrils in the alveolar bone and cementum during deposition, thus acting as an anchorage zone for the teeth. The remodeling of the fibrous system on the tension side is related to the direction of the pull on the tooth resulting in the production of new fibers in that direction. Most of the relapse tendency is caused by the structures
  • 22. Reiton has evaluated the degree of relapse following tipping without retention and concluded that: – Some amount of relapse occurs immediately after 2 hours of removing the appliance as the tooth begins to upright within the PDL space. – After 4 days, the tooth comes to a stand still due to formation of the hyalinization area on the tension side. – After elimination of the hyalinised area, relapse continues. – Unlike PDL, the supra-crestal alveolar fibers are not anchored in the bony wall and hence they cannot be readily remodeled. Hence they have less chance of being reorganized. Remodeling of the gingival
  • 23. – These gingival fibers are slow to remodel after tooth movement, as the main function of these fiber groups is to protect the alveolar processes and maintain tooth position and interproximal contact. – The transseptal fiber stabilizes the teeth against separating forces and may actually maintain the contacts of adjacent teeth. – Removal of proximal teeth contacts will allow the transseptal fibers to contract and produce approximation of adjacent teeth. – Surgical pre-incision of supra alveolar structures (fibrotomy) may prevent or reduce relapse.
  • 24. – The fibrils connecting heavy frenulum attachments to the alveolar processes need a very long period of remodeling. – Stress induced by orthodontic forces lead to increased formation of “oxytalan”. Increased presence of oxytalan in periodontium under stress situations is associated with an increase in vascular activity, rather than an attempt to support and strengthen the tooth position. – Fiber bundles on the tension side tend to become arranged according to the physiologic movement of the tooth. During retention, new bone fills the space between bone spicules. This arrangement and calcification of new bone spicules results in a fairly dense bone tissue, which will prevent relapse.
  • 25. Retention is necessary for three reasons: The gingival and periodontal tissues are affected by orthodontic tooth movements and require time for reorganization, when an active appliance is removed. After treatment, the teeth are in unstable condition. So the soft tissue pressures constantly produce relapse tendency. Growth changes can alter orthodontic results.
  • 26. Reorganization of Periodontal Tissues: Orthodontic tooth movement requires widening of PDL space and disruption of the collagen fiber bundles. Restoration of the normal PDL architecture begins once the teeth can respond individually to the forces of mastication. It requires 3-4 months period and the little amount of mobility that is present at appliance removal disappears. Small but prolonged imbalances in tongue, lip-cheek pressures or pressure from gingival fibers are resisted by “active stabilization”.
  • 27. The disruption of PDL due to orthodontic tooth movement has little effect on stabilization on occlusal forces, but it reduces or eliminates the active stabilization. This means that immediately after the orthodontic appliances are removed, teeth will be unstable in the face of occlusal and soft tissue pressures.
  • 28.  The gingival fiber networks must also remodel to accommodate the new tooth positions. Both collagenous and elastic fibers of the gingiva are very slow at reorganization.  Collagen fibers requires 4-6 months to reorganize but the elastic supracrestal fibers are extremely slow at reorganization and are capable of exerting forces capable of displacing teeth one year after removal of appliance.  Patients with severe rotations, sectioning the supracrestal fibers around the severely malposed or rotated teeth (just before the time of appliance removal) is a recommended procedure, as it reduces
  • 29. Principles of Retention: Teeth will tend to move back in the direction form which they came due to the elastic recoil of gingival fibers and due to the unbalanced tongue lip forces. Teeth require full time retention for first 3 to 4 months. To promote reorganization of the PDL the teeth should be free to flex individually during mastication as the alveolar bone bends in response to heavy occlusal loads..
  • 30. Due to the slow response of the gingival fibers, retention is continued for 12 months and can be reduced to part time wear after the first 3-4 months. In adult patients who are not growing, permanent retention may be required because of lip, cheeks and tongue pressures that are too large to balance out. Patients who are growing, usually need retention until growth has reduced to the low levels that characterize adult life.
  • 31. Occlusal Changes Related To Growth: Skeletal problems tend to recur in all three planes of space, if growth continues. As the transverse growth is completed first, it causes less of a problem clinically than changes from late anteroposterior and vertical growth. Skeletal growth tends to recur as in most of the patients the original growth pattern continues as long as they are growing.
  • 32.  Orthodontic treatment is done mostly in early permanent dentition, goes on for 18-30 months; meaning that active growth treatment will conclude by the age of 14-15 years.  Very slow growth continues throughout adult life and the same pattern that led to malocclusion in the first place can contribute to deterioration in occlusal relationship, many years after treatment.
  • 33. Factors affecting retention 1. Forces from PDL and gingiva 2. Forces from Soft Tissue a) Lower labial segment b) Arch width/Bicanine/Bimolar c) Arch length d) Overjet depends on lip position /size 3. Occlusal factors aid stability a) Correction or Class II to Class I b) Multi directional chewing pattern c) Post treatment facial growth and development. 4. Axial Inclinations: The further orthodontist have retracted mandibular incisor the further they have to retract maxillary incisor. Tipping it to upright results in deep bite.
  • 34. Conditions requiring retention 1) No Retention Required i) Corrected cross bites Anterior Posterior ii) Dentition treatment by serial extractions iii) Correction achieved by retardation of maxillary growth once the patient has passed through growth period. iv) Maxillary and mandibular teeth whose separated to allow for eruption of teeth previously blocked.
  • 35. 2) Limited Retention Class I non extraction cases with protrusion of incisors. Class I or class II extraction case, particularly in maxillary arch until lip and tongue pressure becomes normal. Retainers/Headgears can be used Corrected deep bite. Overbite correction achieved as the result of bite opening Severe occlusal plane tipping Mild to moderate correction of rotated teeth-Gingivectomy Ectopic eruption/presence of supernumerary teeth these tooth have tendency to intrude themselves when released Excessive spacing between maxillary incisors Class II division II because of increase in intercanine width
  • 36. 3) Permanent/Semi-permanent Retention  Cases in which mandibular arch was expanded cases of generalized spacing instances of severe rotations diastema.
  • 37. Retention for Class II Correction: Relapse is usually due to the forward movement of maxillary teeth and backward movement in the lower arch, and the differential growth of the maxilla in relation to the mandible. Tooth movement is caused by local periodontal and gingival factors and it can be an important short term problem. Whereas the differential jaw growth is a more of a long term problem as it alters jaw position and therefore it contributes to repositioning of the teeth. Overcorrection, during finishing procedure, controls tooth movement that would lead to class II relapse. Even with good retention period, 1-2 mm of posterior change caused by adjustment in tooth
  • 38. Class II elastics tend to move the lower incisors forward during class II correction. – Lip pressure will try to push these incisors upright leading to crowding and return of overbite and overjet. – If more than 2 mm of forward positioning of the lower incisors has been achieved during treatment, permanent retention is required. Long term relapse usually occurs due to differential jaw growth. After active treatment is completed, more of forward growth of maxilla is likely to occur than the mandibular growth. If maxillary growth is restrained by either extraoral force or functional appliance, some amount of post-treatment rebound may occur. This relapse tendency can be controlled with a head gear to upper molar on a reduced basis, in conjunction with a retainer to hold the tooth in alignment.
  • 39. The other method is to use a functional appliance to hold the tooth position and occlusal relationship. For patients with less severe problems, in whom continued growth may or may not cause problems of relapse, conventional maxillary and mandibular retainers can be given. A functional appliance can be worn at night if relapse begins to appear. Severe skeletal problem: 12-24 months of retention. The more the severe initial class II; and the younger the patient during active treatment, the more likely that either headgear or functional appliance will be needed as retainer.
  • 40. Retention after Class III Correction:  Relapse due to mandibular growth is most likely to occur and this stage of growth is difficult to control; not even with a chin cap.  A chin cap tends to rotate the mandible downwards, causing growth to be expressed more vertically and less horizontally.  If facial height is normal or excessive after orthodontic treatment; and relapse occurs due to mandibular growth, the surgical correction after the completion of growth is the only option.  In mild class III, a functional appliance or a positioner is sufficient to maintain occlusal relationship during posttreatment growth.
  • 41. Retention after Deep Bite Correction:  Retention is accomplished using a removable upper retainer with an anterior bite plate so that the lower incisors will contact, if the bite begins to deepen. This retainer does not separate the posterior teeth.  This bite plate is continued as the vertical growth continues into the late teens.  Worn  Bite for several years after fixed treatment. depth can be maintained by wearing the retainer only at night after stability has been achieved.
  • 42. Retention after Open Bite Correction:  Retention by a combination of depression of incisors and elongation of molars.  Active habits --- intrusive forces on incisors --- altered posture of the jaws --- supraeruption of molars.  Relapse of open bite is always due to elongation of the posterior teeth.  Control of openbite relapse --- high pull head gear to the upper molars with a standard removable retainer OR  An appliance with bite blocks between the posterior teeth, which stretches the patient’s soft tissues to provide force opposing eruption.
  • 43. Retention of Lower Incisor Alignment: Skeletal growth has the potential for altering the position of the teeth. If the mandible grows downwards and forwards, the lower teeth get pushed into the lower lip which tipping them distally. For this reason, growth in normal or class III patients is usually associated with lower incisor crowding. A retainer in lower incisor region is adequate to prevent crowding until growth has declined. Orthodontic retention should be continued till the third molars have erupted or have been removed. Full time wear for first 3-4 months. followed by night time wear and then gradually wearing them off.
  • 44. Part time retention: 12 months. In non-growing patients retention is continued till remodeling of the gingival fibers occurs; but if significant amount of growth is remaining, part time retention is only needed until completion of growth. All cases treated in early permanent dentition require retention of anterior alignment till the late teens. If permanent retention is needed, fixed retainer can be used for intra-arch relation.
  • 45. Removable Appliances: Hawley Retainer:  Designed in 1920 as an active removable appliance.  Incorporates clasps on molar teeth and an outer labial bow with adjustment loops spanning from canine to canine.  Earlier fully banded retainers were used, hence after debanding some amount of space was always remaining. Hence, Hawley appliance was used as an appliance for closing band spaces.
  • 46. In first premolar extraction cases, the standard design of Hawley retainer cannot be used as its labial bow extends across the first premolar extraction space, tendency to wedge it open.
  • 47. Modification  The bow can be soldered to the buccal segment of the Adam’s clasps or
  • 48.  Labial bow is wrapped around the entire arch using circumferential clasps on second molars for retention Circumferential clasp on the last molars or lingual extension clasps can be used instead of the Adam’s clasp, if the occlusion is tight.
  • 49.  The palatal coverage of any removable retainer can be used for the addition of bite plane lingual to the upper incisors to correct bite depth.  The lower retainer is somewhat fragile and may be difficult to insert because of undercuts in the premolar and molar region.
  • 50. Positioner  Excellent finishing device  Uncomfortable for patient  Sleep well tolerated  They do not retain rotations well  Overbite tends to increase while the positioner being worn.
  • 51. Drawbacks: Tooth Positioners: The pattern of wear of positioner does not match the pattern usually desired for retainers. • Difficult to wear full time. • Positioners do not retain incisor irregularities and rotations as well as standard retainers. The reason being that the retainers require full time wear initially, and positioners are worn only for about 4 hours. Advantage Tooth Positioners: Maintains occlusal relationships and intra-arch tooth positions. For a patient with class III relapse tendency, a positioner made with jaws related somewhat downwards and backwards may be useful.
  • 52. Fixed Retainers: Indications:  Maintenance of lower incisor position during growth: Even a small amount of growth between the age 16 and 20 can cause re-crowding. Relapse is always accompanied by lingual tipping of the central and lateral incisors.  A fixed lingual canine to canine retainer can be fabricated with bands on the canines or can be bonded to the lingual surface.
  • 53. A fixed lingual bar attached only to the canines and resting against the flat lingual surfaces of the lower incisors above the cingulum. This prevents the canines and incisors from moving lingually an defective in maintaining corrections of rotations. Disadvantage:  Creating band space can be a problem unless bands are used during treatment.  Labial part of the band tends to trap plaque leading to decalcification.
  • 54.  It is attached only to the canines, resting passively against the central and lateral incisors.  It is also possible to bond a fixed lingual retainer to one or more of incisor teeth. Indicated in severely rotated teeth.  If the span of retainer wire is bonded on an intermediate tooth or teeth, a more flexible wire should be used. E.g. Braided SS arch wire.
  • 55. Diastema Maintenance:  This is another indication for fixed permanent retention, especially if the diastema between the maxillary central incisors has been closed.  Even if frenectomy is done, there is tendency for the incisors to open up.  A bonded section of flexible wire can be used, contoured in such a way that it lies near the cingulum to keep it away from the occlusal contact.  Objective of the retainer is to hold the teeth together while allowing them some mobility to move independently during function.
  • 56. Maintenance Of Pontic Space:  A fixed retainer is the last choice to maintain a space where bridge pontic will be eventually placed.  A heavy intra-coronal wire bonded in a shallow preparation in the future abutment should be used. Longer the span --- heavier the wire.
  • 57. Maintenance of Extraction Space:  A fixed retainer is more reliable and better tolerated than a full time removable retainer. Spaces reopen unless the retainer is worn constantly.  It is always better in adults to bond the fixed retainer on the facial surface of the posterior teeth when spaces have been closed.  Disadvantage: Difficult to maintain hygiene.
  • 58. Active Retainers:  “Active retainers” is a misnomer as a device cannot be actively moving the teeth and serve as a retainer at the same time.  Relapse or growth change may require minor tooth movements to be carried out during retention period. This is usually done with a removable appliance that continues to act as a retainer after it has repositioned the teeth. E.g. Hawley retainer.
  • 59. Essix Retainers: Jan 1997 JCO, JOHN J. SHERIDAN, MCMINN, Orthodontists' concept of retention is moving toward the idea that teeth will move unless retained indefinitely. The cornerstone of Essix permanent retention is the complete delegation of responsibility to the patient. Essix .75mm (.030") thermoplastic copolyester is mandatory for the fabrication of Essix retainers. Thinner, 0.5mm material is too flimsy, while thicker, l mm material lacks flexibility. Copolyester, unlike polycarbonates, does not require heat treatment before thermoforming. It is much stronger, clearer, and resistant to abrasion than acrylic sheet, and thus produces thinner yet sturdier appliances.
  • 60. They are a thinner, but stronger, cuspid-to-cuspid version of the full-arch, vacuum-formed devices. Advantages include: The ability to supervise without office visits. Absolute stability of the anterior teeth. Durability and ease of cleaning. Low cost and ease of fabrication. Minimal bulk and thickness (.015"). The brilliant appearance of the teeth is caused by light reflection.
  • 61. Permanent Lingual Bonded Retainer JEREMY D. ORCHIN, DDS JCO 1990 Apr. Lingual Bonded Retainer Kit includes a specially formulated Fiberthread (Kevlar) and light-cured composite resin . Fiberthread has four times the strength of stainless steel of equal dimensions, allowing the use of thread about .010 " in diameter. It is soft and flexible prior to bonding, which permits easy and rapid adaptation to any lingual configuration. The light-cured composite is designed with the proper consistency to integrate with the Fiberthread and provide a strong bond to the prepared enamel surface
  • 62. Patients are impressed with its comfort, ease of maintenance, and appearance. Because the retainer can be placed before removal of all labial brackets, the anterior brackets can be debonded and retention begun during posterior space closure or finishing. The thinness of the material also allows its use, in most cases, as a fixed retainer palatal to the upper incisors
  • 63. Bonded Maxillary Custom Lingual Retainer - FRANK W. KRAUSE, DDS, JCO 1997 Volume 1984 Oct The bonded maxillary custom lingual retainer (MCLR) was designed for alignment and rotational control during retention of maxillary anterior teeth and to help overcome two other major problems associated with bonded lingual retention in the maxillary arch: 1. Tedious and time-consuming. 2. Occlusal stress exerted against maxillary lingual retainers, through direct occlusal contact or biting forces that tend to break bonds.
  • 64. The maxillary custom lingual retainer is constructed of lingual bonding bases joined by a rectangular .018" ´ .022" soft steel wire. The triangular shape and slightly rounded sides and corners of these bases conform well to the lingual anatomy of the incisors.
  • 65. Removable Plastic Herbst Retainer RAYMOND P. HOWE, JCO, 1987 Aug The design of the RPH retainer is similar to that of the Removable Plastic Herbst treatment appliance. Upper and lower plastic splints are fabricated over a supporting wire framework and connected by the Herbst mechanism . The principal difference between the retainer and the treatment appliance is that the retainer has full occlusal coverage on all teeth, including the upper incisors. This maintains tooth positions and prevents passive eruption.
  • 66. Advantages: Retreatment Appliance Post-Surgical Retainer Aid for Obstructive Sleep Apnea Anterior Repositioning Splint
  • 67. Third Molars and Orthodontic Diagnosis ROBERT J. SCHULHOF JCO on 1976 Apr(272 - 281): According to Bjork, approximately 45% of the population will have impacted lower third molars. The eruption of third molars is blamed for relapse in many cases. Extraction of bicuspids has been justified as creation of space for the erupting third molars. Temporomandibular joint problems have been reported to occur both from malposition of third molars and from their absence. Can Erupting Third Molars Cause Crowding? This has been a subject of considerable controversy in orthodontics. Some investigators say yes, others say no. Dr. Leroy Vego determined that arch perimeter loss was, on average, .8mm greater in cases with third molars than in cases with congenitally missing third molars, and this was shown to be statistically significant.
  • 68. Vego's work showed that the probability of a loss of more than 3mm was approximately 8% in cases without third molars, but 33% (more than four times as likely) in cases with erupting third molars. Hence, from this work it can be concluded that, whereas the third molars are not always the reason for teenage mandibular crowding, they are a significant contributor in a great number of cases.
  • 69. Other researchers have reported "no significant differences" between cases with and without third molars. Kaplan concluded: "These data indicate that the third molars does not appear to produce a greater degree of lower anterior crowding and rotational relapse after the cessation of retention The theory that third molars exert pressure on the teeth mesial to them could not be substantiated in this study." A closer look at the details of Kaplan's work shows, however, that the group with erupting third molars had an average of 1mm more crowding than the group with third molar agenesis, almost precisely the same result as Vego obtained.
  • 70. A long-term prospective evaluation of the circumferential supracrestal fiberotomy in alleviating orthodontic relapse AJODO 1988 May - Edwards There are two soft-tissue periodontal entities that may influence the stability of the teeth following orthodontic movement: the supra-alveolar group of fibers and the principal fibers of the periodontal ligament. The method by which these soft tissues might apply a force capable of moving teeth is not clear since these tissues are composed primarily of non-elastic collagenous fibers.
  • 71. In any case the potential for relapse forces in the fibers of the periodontal ligament and transseptal groups most adjacent to the alveolar crest is certainly minimal because these tissues have been shown to possess a dynamic remodeling mechanism that is quite efficient. How does a tissue that is essentially composed of inelastic, non-contractile tissue apply a force? As yet the answer is unknown. One possibility may involve that the length of collagen fiber can be altered by adjusting the ion concentration of its surrounding medium; thus, a mechanism is proposed by which the contractile collagen could "recoil" following orthodontic tooth movement.
  • 72. Another histologic explanation of relapse force may relate to the elastic-like oxytalan fibers that apparently increase in concentration in the supracrestal tissues during the rotational movement of teeth. However, although these oxytalan fibers possess some staining properties similar to elastic fibers, there is no direct evidence that they are physiologically similar to elastic fibers. Fullmer, Sheetz, and Narkates cautioned that oxytalan could actually represent altered collagen fibers. In summary, there is no substantial evidence at the present time to explain the mechanism by which the gingival soft tissues may apply a force capable of moving the teeth.
  • 73. Edwards reported on a simple surgical technique to alleviate the influence that the supracrestal periodontal fibers presumably have on rotational relapse. He has termed the procedure a circumferential supracrestal fiberotomy (CSF) procedure. Basically, this technique consists of inserting a surgical blade into the gingival sulcus and severing the epithelial attachment surrounding the involved teeth. The blade also transects the transseptal fibers by interdentally entering the periodontal ligament space. Although the transseptal groups adjacent to the alveolar crest, as well as the principal fibers of the periodontal ligament, do show relatively rapid reorganization following tooth rotation and thus are presumably not of importance in the relapse mechanism, No surgical dressings are indicated and clinical healing usually is complete in 7 to 10 days.
  • 74. The CSF procedure is not recommended during active movement of the teeth or in cases with gingival inflammation. Although the most obvious condition for the use of the supracrestal fiberotomies is that of the rotated tooth, the procedure has also been recommended following labiolingual orthodontic tooth movement.
  • 75. The logic of modern retention procedures Henry Kaplan AJO-DO 1988 Apr (325-340): Hellman's (1936)7 statement that ''We are almost in complete ignorance of the factors which pertain to retention for the individual patient.“ Reitan's (1959, 1966, 1967) microscopic studies of postretention treatment changes excited the orthodontic community worldwide. He demonstrated in animal studies that the supracrestal gingival fibers (collagenous) appear histologically taut and directionally deviated after tooth rotation, and that this condition did not lessen even after years of retention.
  • 76. Williams (1985),188 in addition to stripping, added five other treatment "keys," which he said will eliminate the need for lower retainers, but he showed a 2-year follow-up of one case. These approaches and that of Peck and Peck's (1972)61 reproximation studies are seemingly based upon the theoretical concept of polished broad contact areas described by Begg in Stone Age men. Begg made the deduction that it was the primitive rough diet of the Australian aborigines that was responsible for well-aligned teeth. On the other hand, it was believed that failure to achieve polished broad contact areas during and following orthodontic treatment of modern civilized man with a lack of comparable attrition would require a technique for realignment and stripping of crowded lower incisors to prevent or correct relapse.
  • 77. Muchnic informed his patients: In most cases the retention period was planned with expected growth and maturation in mind, because the forces which work so efficiently in treatment to inhibit growth in one area while allowing growth to continue in another should not necessarily be discontinued because the bands have been removed and the teeth are in proper occlusion. He has gone to the extent of informing the patient that there is 33% chance of relapse not occurring in every case i.e one in every three case will not relapse.
  • 78.  Evidence of instability is often first noted by progressive crowding of mandibular incisors following removal of retaining devices. Whatever may be the of causes of relapse, mandibular irregularity is the precursor of maxillary crowding, deepening of the overbite, and generalized deterioration of the treated case."  Second, the popular conceptions of greater stability of a case post-retention, such as maintaining canine and molar width, were usually upheld, but in some cases it did not ensure stability because mandibular incisor relapse occurred even when intra-canine width was not violated in treatment
  • 79.  Third, how does the orthodontist reconcile the statements that arch length could almost never be increased and as a rule decreased postretention with the finding of another study that "Premolar width expansion in non extraction treatment has only slight tendency to decrease post retention"? The latter would seem to lead to anterior crowding.  Fourth, serial extraction procedures followed by full orthodontic treatment showed more stability, but some incisor relapse was still reported for these cases in post-retention studies even though early rotations had been performed and held during a growth period.
  • 80.  What then are the conclusions of this article that are of significance to the orthodontist in addressing the patient's recurring question about the need and duration of retention?  It is suggested that the clinician simply tell the patient in understandable language what is and what is not known about the "state of the art" of retention that is applicable to the individual, whose facial- dental objectives of treatment have been satisfactorily achieved.
  • 81. 1There are very few cases requiring minimum or no retaining appliances and these would include: a. Blocked out canines in Class I extraction cases with no crowding b. Class I anterior and/or posterior crossbites with very steep cusps and no anterior crowding c. Class II cases slightly over-treated with sufficient arch length indicated by mandibular anterior spacing and absolutely no mandibular incisor rotations 2. Routine cases, extraction or nonextraction, should have retaining appliances— fixed or removable. a. At least until the destiny of the third molar teeth is determined [or] b. Until the growth process has slowed in late teens and early twenties [and] c. Afterward at the option of the patient
  • 82. 3. Cases that will need indefinite retention a. Class II, Division 2 Angle deep bite cases b. Arch expansion treatment for esthetic demands c. Patients with uncontrolled muscular or tongue habits 4. Cases that require operative procedures with indefinite retention a. Treatment limitations such as tooth size discrepancies may result in increased overbite or super Class I. b. larger mandibular teeth will result in end-to-end incisor relationships, maxillary spacing, or buccal endon occlusion. c. Stripping or reproximation of oversized teeth and esthetic bonding of malshaped or undersized teeth may help resolve this problem. d. A vertical incisal relationship, which cannot be
  • 83. 5. Cases requiring special construction and/or renewal of removable retaining appliances or acrylic on the labial bows a. Posttreatment adolescent palatal changes b. Late mandibular growth spurt139 and Tweed type C growers c. To maintain torque and overbite correction 6. The orthodontist can never be completely certain that the individual case will be in the 33% that will not relapse, even if only mildly. 7. The patient should be apprised of the expected changes of the maturing dentition, especially of mandibular and maxillary crowding
  • 84. Finally, in this era of informed patient consent, what then, in the opinion of the author, is the logical answer to the question of when the orthodontist has the-sole option of prescribing very limited retention or no retention? The answer is only when there is absolute certainty that there will be no relapse.
  • 85. Summary: Occlusion is a result of developmental processes in which the main events are facial growth, dental development, and function. These genetically and environmentally conditioned processes continue to change throughout life, showing significant individual variation. The dynamics of facial development with variations in maxillary and mandibular growth, together with dento-alveolar development need to be better understood before orthodontist can expect to achieve more stable treatment results. Although appliances and mechanics used for correction of malocclusion have improved in recent decades, the identification of the etiologic factors that cause relapse has proven elusive.
  • 86. To conclude: Quote Norman Kingsley (1908), "Father of Orthodontia," in his last published article, had these prophetic words to say about retention “It is not so difficult to straighten crooked teeth, to get the dental system into a position acceptable to your patients and yourself, but to hold it there until it becomes permanently settled, is a much more serious problem. It is the one important consideration in all your prognosis, and the success of orthodontia as a science and as art lies in the [retainer].... Do not discharge the case or abandon retainers until there is a reasonable expectation of permanence. You may rightfully ask of that experience, how long will that be? Your patient will pester you with the same query. Out of the same observation and experience I can only answer, I am agnostic, I don't know, in each and every individual case I do not know.
  • 87. Thank you