EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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CHAPTER 1. INTRODUCTION The intent of orthodontic treatment is the “correction and prevention of malocclusion of the teeth” (Tweed 1941, p 5), but the maintenance of the corrections has plagued orthodontists possibly since the inception of the specialty. Hellman (1944) described orthodontic relapse as disturbances occurring in cases that have been successfully treated that lead to a return of the teeth to an undesirable state that may not necessarily resemble the original malocclusion. Because of the public’s perception that orthodontic treatment results should persist indefinitely (Graber 1966) and the fact that stability continues to be a challenge for orthodontists, evidence-based studies are needed to provide information aimed at minimizing relapse. Whether or not individual cases can be viewed as successful or not needs to be evaluated by the stability of treatment results. Rationale and methods of retention following orthodontic treatment continue to be a popular, yet contentious topic within the specialty (Little et al. 1988; Atack et al. 2007; Cerny and Lloyd 2008). Relapse is the tendency of teeth, which were moved orthodontically to new positions during treatment that may not be well stabilized by the musculature, periodontium and other supporting structures, to return towards their more stable, pretreatment positions (Joondeph and Riedel 1994). Reitan (1959) proposed that teeth tend to return to their pretreatment positions during a period of time following orthodontic correction. In an attempt to establish whether an “equilibrium position” of the postorthodontic dentition is possible, Weinstein et al. (1963) attempted to identify and quantify the effects that various environmental factors might have. Currently however, the various factors proposed to contribute to relapse remain incompletely understood, giving rise to differences in retention protocols among clinicians (Melrose and Millett 1998). Instability of the dentition following orthodontic treatment exists to some degree in practically every patient (Graber 1994), yet attempts to quantify this degree have proven to be unpredictable (Little et al. 1981). It is widely accepted that the mandibular incisors are the teeth most commonly affected by relapse. In Massler’s study based on 2,758 adolescents ranging in ages from 14 to 18 years old, he gave statistical evidence that the mandibular central incisors are the most frequently maloccluded teeth, followed by the mandibular lateral incisors (Massler 1951). Broadbent (1943) and Fastlicht (1970) also noted the higher incidence of crowding in the lower incisor region as compared to other areas of the dentition in both treated and untreated people. 1
Joondeph and Riedel (1994, p 908) defined orthodontic retention as “…the holding of teeth in ideal esthetic and functional positions.” The goal of retention is to counteract forces that might affect the teeth as a result of their new positions in the oral environment until such time as the teeth and supporting tissues have become reoriented to the new position. The standard Hawley retainer and the fixed mandibular canine-to-canine retainer have remained popular methods to help achieve these goals and are in routine use by many orthodontists today. Some orthodontists suggest that fixed retention is the only way of ensuring a stable result (Angle 1907; Little et al. 1988), while others contend that removable appliances are required to enable the supporting tissues to adapt to the functional demands placed on them (Hawley 1919; Markus 1938; Waldron 1942). Studies have documented the importance of retention as a helpful adjunct of orthodontic treatment to retard relapse, but few studies offer long-term information focusing on the benefits of temporary fixed retention of the mandibular anterior teeth. Due to the scarcity of research is this area and because ambiguities regarding posttreatment retention and relapse continue to exist in both the literature and among practitioners, the present study aims to review the retention problem and address the effectiveness of placing mandibular canine-to-canine fixed retention for a period of two to three years following comprehensive orthodontic treatment. The purpose of the present research project is to evaluate Incisor Irregularity and relapse in a sample of people at long-term recall who were treated with temporary fixed mandibular retention following comprehensive orthodontic treatment, and compare these results to a similar group of patients at long-term recall who were given removable retention, i.e., standard Hawley type retainers at posttreatment. By evaluating pretreatment, posttreatment and longterm recall records of patients all treated under a single treatment philosophy, an effort is made to clarify the effects of using prolonged mandibular fixed retention on long-term stability. 2
Page 1 and 2: EFFICACY OF TEMPORARY FIXED RETENTI
Page 3 and 4: DEDICATION This thesis is dedicated
Page 5 and 6: ABSTRACT Instability of the occlusi
Page 7 and 8: CHAPTER 5. DISCUSSION .............
Page 9 and 10: LIST OF FIGURES Figure 3-1. All cas
Page 11: Figure 4-14. Box plot of the distri
Page 15 and 16: Strang (1952, p 794) claimed that
Page 17 and 18: malocclusion must be maintained if
Page 19 and 20: e aimed at maintaining, in most ins
Page 21 and 22: three time intervals: during treatm
Page 23 and 24: mechanical treatment does not neces
Page 25 and 26: elation, the masticatory system wil
Page 27 and 28: exerted on the denture from the buc
Page 29 and 30: In summary, the variance in tongue
Page 31 and 32: Sinclair and Little (1983, p 114) a
Page 33 and 34: Study and 43 orthodontically treate
Page 35 and 36: and Sakols 1982; Vaden et al. 1997;
Page 37 and 38: years postretention. Årtun et al.
Page 39 and 40: adjustment, if necessary. This abil
Page 41 and 42: Duration of Retention The premise i
Page 43 and 44: The reduction in tooth structure of
Page 45 and 46: 4. The most stable position of the
Page 47 and 48: CHAPTER 3. MATERIALS AND METHODS Sa
Page 49 and 50: The present sample consisted of the
Page 51 and 52: Figure 3-2. Illustration of how mol
Page 53 and 54: Figure 3-3. Illustration showing di
Page 55 and 56: Figure 3-5. Illustration showing mi
Page 57 and 58: Figure 3-6. Illustration showing an
Page 59 and 60: Figure 3-8. Illustration showing in
Page 61 and 62: 34. LR3 cusp tip point. 35. Right d
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Figure 3-10. Illustration showing o
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Figure 3-11. Illustration of Inciso
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3. Go, Gonion (anatomic): The most
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Figure 3-13. Depiction of the angle
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Figure 3-15. Illustration of the me
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Figure 3-17. Illustration of the me
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Figure 3-19. Illustration of the an
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Figure 3-21. Illustration of the up
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Figure 3-22. Illustration of the to
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Figure 3-24. Illustration of the po
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the “older” Tweed force system,
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The null hypothesis is: There was n
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Figure 4-1. Distribution of the 166
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occlusal issues are tolerated by bo
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40 35 30 FMA (degrees) 25 20 15 10
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Figure 4-4. Plot of the average val
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larger ANB at the recall examinatio
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21 19 Total Chin (mm) 17 15 13 11 9
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Figure 4-8. Box plot of the distrib
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which a Class I relationship was no
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Figure 4-11. Plot of mean Curve of
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Figure 4-13. Box plot of the distri
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Table A-4 addresses the question of
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Figure 4-16. Bar chart of the avera
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only sample changed significantly m
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3 2 1 0 Canonical Variate 2 -1 -2 R
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8 Anterior Discrepancy (ADisc) 6 4
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40 Incisor Aspect Ratio (IAR) 30 20
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1.5 Incisor Segment Depth (ISD) 1 0
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more stable (i.e., the mean change
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Molar Correction (MC) 10 8 6 4 2 0
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Anterior Segment Width (ASW) 1 0 -1
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final vertical positions. This phas
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decreased in both arches during the
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Figure 5-1. Plot of average Incisor
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Based on the present results, the u
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these variables indicate more anter
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and the hassle associated with plac
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Figure 5-2. Scatter-plot graph refl
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stability?” and “for how long?
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About two-thirds (64%) of the corre
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Baume LJ, Horowitz HS, Summers CJ,
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Case CS. Techniques and principles
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Glenn G, Sinclair PM, Alexander RG.
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Joondeph DR. Retention and relapse.
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Littlewood SJ, Millett DT, Doubleda
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Ormiston JP, Huang GJ, Little RM, D
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Rosenstein SW, Jacobson BN. Retenti
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Steadman SR. A philosophy and pract
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Zachrisson BU, Büyükyilmaz T. Bon
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Table A-1. Descriptive statistics a
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Table A-2. Descriptive statistics a
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Table A-3. Descriptive statistics f
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APPENDIX B. ANCOVA TESTS OF THE COM
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Table B-1. Continued. Sex Retention
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Table C-1. Results of ANCOVA tests
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Table D-1. Descriptive statistics,
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Table E-1. Two-way ANOVA tests eval
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VITA Mark Owens was born on January
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EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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