Lower labial segment crowding by almuzian

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Lower labial segment crowding by almuzian

  1. 1. Dr. Mohammed ALMUZIAN Page 0 UNIVERSITY OF GLASGOW Lower labial segment crowding Personal notes Dr. Mohammed ALMUZIAN 1/1/2013
  2. 2. Mohammed Almuzian, University of Glasgow, 2013 Page 1 Table of Contents Terminology............................................................................................................................................1 Incidences ...............................................................................................................................................1 Classification of crowding......................................................................................................................2 The risk factors .......................................................................................................................................2 The aetiological factors...........................................................................................................................3 Lower incisor crowding & Third molar debate ......................................................................................4 Treatment................................................................................................................................................5 Factors that should be considered.......................................................................................................5 The treatment options .........................................................................................................................5 Evidences................................................................................................................................................6 Lower labial segment crowding Main article Richardson 1994 AJO and Richardson 2002 Dental update Terminology  Tertiary Crowding,  Late Secondary Crowding,  Post-Adolescent Crowding Incidences  Late crowding of the mandibular incisors beginning between the ages of 17 and mid-twenties and progressing through into late adult life is common (Sakuda 1976).
  3. 3. Mohammed Almuzian, University of Glasgow, 2013 Page 2  approximately 2/3 of adolescents with good alignment and “normal” occlusions will develop incisor irregularity be early adulthood  Richardson (1982) reported that patients with crowding of the early permanent dentition are more likely to result in impaction of the third molars. Classification of crowding Van der Linden 1974 1. Primary crowding refers to a discrepancy of tooth dimension and jaw size, mainly determined genetically. 2. Secondary crowding is caused by environmental factors, including local space conditions in the dental arches and the position and function of the tongue, the lips and the buccal musculature. 3. Tertiary crowding occurs during adolescence and post-adolescence with a predilection for the lower labial segment. The risk factors 1. patients at pretreatment with excess overjet and/or excess overbite prone to more relapse. (Little 1999) 2. Vertical facial growth also a risk factor for stability. (Little 1999) 3. Pre-existing tooth tissue discrepancy:  Robinson (1981) demonstrated an association between the degree of lower labial segment crowding in the early dentition and the degree of crowding in the late adolescence, in a group of treated patients.  The presence of LLS crowding increase the risk of posttreatment relapse. For each 1mm of LLS crowding there is a chance of 4-18% of relapse (Fudalej 2008). 4. Teeth morphology  Peck and Peck 1976 found that crowding is slightly more common in persons whose teeth have large mesiodistal dimensions than in those with smaller teeth
  4. 4. Mohammed Almuzian, University of Glasgow, 2013 Page 3 due to the theory of contact point slippage. However (Little 1999) found no correlation. 5. PD compromised dentition 6. Extraction less than non-extraction 7. Orthodontic treatment: Teeth that have been moved orthodontically have a natural tendency to return to their original (crowded) positions especially excessive arch expansion in the canine region have a strong tendency to relapse. The aetiological factors 1. Lack of attrition:Begg (1954). 2. Soft tissue maturation:  Van der Linden (1979) Late mandibular growth changes may bring the lower incisors into a different soft tissue environment causing retroclination and crowding  Bench 1952 found that the hyoid bone and tongue descend with age, relative to surrounding structures, causing imbalance between lip and tongue and resulting in crowding 3. Late anterior growth and mandibular remodelling:  Continued growth of the mandible after the cessation of maxillary growth may cause lower incisors crowding (Moore, 1960). 4. Anterior component of occlusal forces:  Van Beek (1979) the anterior component of the force of occlusion on mesially inclined teeth,  Occlusal changes may also be caused by restorations, tooth loss with drifting, or the development of grinding habits 5. Mesial vectors of muscular contraction, 6. Degenerative periodontal changes allowing teeth to drift under light pressures;
  5. 5. Mohammed Almuzian, University of Glasgow, 2013 Page 4 7. Mesial drift of posterior teeth by trans-septal fibres (Stephens and Houston, 1984). 8. Tooth size and shape which can result in contact point displacement (Kahl- Nieke et al, 1995) 9. The mandibular third molar: Mandibular third molars–presence and position. Richardson in his study 1984 found that patient with impacted molars develops more crowding and have bigger molars than non-impacted group. Lower incisor crowding & Third molar debate Studies relating third molars to crowding 1. Jensen study (1960) they have examined 60 dental students (33 persons with unilateral third molar aplasia in the maxilla and 30 in the lower. They have found that in both maxilla and mandible there was a greater degree of crowding on the side where the third molar was present. 2. Richardson and Mills (1990) have compared the mesial drift and change in crowding over a 5-year period in 30 subjects whose lower second molar were extracted between age 11 and 17 years and 30 subjects whose lower second molars were not extracted. They have measured the arch length on the dental casts. They suggested that the presence of a developing third molar can, in some cases, cause forward movement of buccal teeth with an increase in crowding and that the extraction of second molar is effective in reducing the incidence of late lower arch crowding and third molar impaction.. Studies indicating lack of correlation between third molars and 1. Ades at al., (1990) 4 study groups all a minimum of 10 years post retention (Washington group)  Absent 8s
  6. 6. Mohammed Almuzian, University of Glasgow, 2013 Page 5  Impacted 8s  Erupted and functional  Extracted at least 10 years before post retention records No significant differences in mandibular growth or LLS crowding between any of the subgroups. 2. Harradine et al., (1998) RCT on patients randomly allocated into third molar extraction and non- extraction groups. Found very small decrease in LLS irregularity in patients who had had lower third molars removed, not statistically or clinically significant. Treatment Factors that should be considered 1. OH 2. Clinical condition of the teeth 3. Patient and clinician preference must be taken into consideration. 4. Amount of the attached gingiva 5. Overjet and overbite 6. Degree and site of crowding 7. Canine inclination The treatment options 1. Accept 2. Prophylactic measurement: IPS as prophylactic measure had been described by Peck and Peck 1974 3. Permanent retainer (Sadowsky)
  7. 7. Mohammed Almuzian, University of Glasgow, 2013 Page 6 4. In the presence of significant malocclusion, incisor crowding is best managed as part of a comprehensive orthodontic treatment plan either by IPS, extraction or proclination with permanent retention. 5. Yu 2013 Cochrane review. In this review there are no trials published between 1950 and 2012 in which patients were randomly treated with either fixed braces, removable retainers or no treatment. Evidences 1. Gum recession:  Aziz 2011, No association between appliance-induced labial movement of mandibular incisors and gingival recession was found. Factors that may lead to gingival recession after orthodontic tipping and/or translation movement were identified as a reduced thickness of the free gingival margin, a narrow mandibular symphysis, inadequate plaque control and aggressive tooth brushing 2. Relapse:  Paquette et al (1992) also found that cases which had been treated with an average of 2.8 mm. more lower incisor proclination than another matched group of cases, finished with slightly greater irregularity (Little’s index) out of retention. The difference in post-treatment relapse of irregularity between the two groups was very small (0.6 mm), but the findings did suggest that labial movement of lower incisors during treatment does, on average, increase the chance of subsequent relapse.  Ackerman and Proffit (1997) propose an approximate limit of 2 mm for labial movement of the lower incisors if antero-posterior stability is the main factor influencing our decision.  Johnston and Magnusson 2010 retrospectively found less LLS crowding in extraction cases. 3. Retention:
  8. 8. Mohammed Almuzian, University of Glasgow, 2013 Page 7  The work of Little and others quoted above has shown that although larger lower incisor changes in position are less stable, lower incisor alignment tends to deteriorate after retention whether or not the lower incisor position has been maintained  Rowland 2008 found PFR is more efficient in a maintaining the LLS position post ortho.

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