EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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Conflicting evidence regarding third molar effects on posttreatment mandibular incisor crowding has previously been discussed. In an effort to negate any potential impact on stability, third molars are routinely extracted following orthodontic treatment. Retention, in these cases is kept in place until the problem of the third molars has been resolved (Rosenstein and Jacobsen 1971). Overcorrection is another technique aimed at minimizing relapse of teeth. This is commonly considered during treatment of rotated teeth. The thought is that by over-rotating the offending tooth with the notion that the there will be some tendency for the tooth to rotate back towards its former position. However, there is little evidence to indicate that over rotation is successful in preventing this type of relapse (Riedel 1960; Edwards 1970) and the amount of overcorrection needed to achieve stability is unknown. Another treatment protocol involves the paralleling of tooth roots and evenly spacing them from each other during the finishing stages of orthodontic treatment. Rosenstein and Jacobson (1971) claim that if specific care is used to parallel the roots of the teeth adjacent to the extraction sites, then relapse becomes less of a problem. Based on clinical experience and research conducted on over 10,000 of his completed cases, Alexander (2008) contends that proper bracket placement will allow for proper root positioning, i.e., the roots of the anterior teeth should be divergent and the roots of teeth adjacent to extraction sites should be parallel to each other. Summary The current consensus regarding the retention of posttreatment results can be found in the six conclusions drawn by Blake and Bibby (1998) in their literature review of retention and stability: 1. The patient’s pretreatment lower arch form should be maintained during orthodontic treatment as much as possible. 2. Original lower intercanine width should be maintained as much as possible because expansion of lower intercanine width is the most predictable of all orthodontic relapse. 3. Mandibular arch length decreases with time. 33
4. The most stable position of the lower incisor is its pretreatment position. Advancing the lower incisors is unstable and should be considered as seriously compromising lower anterior posttreatment stability. 5. Fiberotomy is an effective means of reducing rotational relapse. 6. Lower incisor reproximation enhances posttreatment stability. Significance of Research Many orthodontists use fixed retention appliances following orthodontic treatment as a means of maintaining treatment results. These appliances incorporate the use of either a braided or solid, round stainless steel wire bonded to the lingual surfaces of the maxillary central incisors or mandibular canines. The purpose of this appliance is to provide a retentive appliance that will allow for semi-rigid fixation of the anterior segment of the dentition without having to rely on patient compliance. Evidence supporting the need for fixed retention is conflicting. Studies conducted at the University of Washington by Little and coworkers (1981 and 1988) concluded that: long-term stability following mandibular anterior alignment was unpredictable; anterior crowding continued during the 10 and 20 year recall period; future stability of cases was unpredictable; and the majority of patients displayed unsatisfactory incisor alignment following retention. Thus, it is the contention of Little that fixed retention is the only way to maintain longterm post-orthodontic stability. However, Andrews (1972, p 307) stated that, “Lower teeth need not be retained after maturity and extraction of the third molars, except in cases where it was not possible to honor the musculature during the treatment and those cases in which abnormal environmental or hereditary factors exist.” Furthermore, Boley (2007) concluded that, based on his review of the literature, stability is a reasonable and predictable goal following orthodontic treatment as long as certain parameters are met. Some practitioners advocate fixed retention only for a temporary period of time following treatment, such as 2 to 3 years. This notion is supported by the research of Al Yami et al. (1999) who evaluated the dental casts of 1,016 patients for long-term stability of orthodontic treatment using the Peer Assessment Rating index. About half of the total relapse took place in the first two years following retention, and all aspects of occlusion relapsed gradually over time but became stable after 5 years with the exception of the mandibular incisors. The presence of fixed retention had a significant impact on relapse at 5 and 10 years 34
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 and 12: Figure 4-14. Box plot of the distri
Page 13 and 14: Joondeph and Riedel (1994, p 908) d
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: The reduction in tooth structure of
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
Page 63 and 64: Figure 3-10. Illustration showing o
Page 65 and 66: Figure 3-11. Illustration of Inciso
Page 67 and 68: 3. Go, Gonion (anatomic): The most
Page 69 and 70: Figure 3-13. Depiction of the angle
Page 71 and 72: Figure 3-15. Illustration of the me
Page 73 and 74: Figure 3-17. Illustration of the me
Page 75 and 76: Figure 3-19. Illustration of the an
Page 77 and 78: Figure 3-21. Illustration of the up
Page 79 and 80: Figure 3-22. Illustration of the to
Page 81 and 82: Figure 3-24. Illustration of the po
Page 83 and 84: the “older” Tweed force system,
Page 85 and 86: The null hypothesis is: There was n
Page 87 and 88: Figure 4-1. Distribution of the 166
Page 89 and 90: occlusal issues are tolerated by bo
Page 91 and 92: 40 35 30 FMA (degrees) 25 20 15 10
Page 93 and 94: 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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