EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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CHAPTER 6. SUMMARY AND CONCLUSIONS Postretention results are the method used to measure the success of orthodontic diagnosis and treatment. Tirk (1965, p 165) said, “The result of orthodontic therapy—good, bad, or indifferent—is only evident many years out of retention.” This longitudinal cephalometric and cast analysis examined the diagnostic records of cases treated comprehensively by several experienced orthodontists who use standard Edgewise mechanics. Of the 166 cases, 69 patients (23 males; 46 females) had been placed in a fixed mandibular canine-to-canine retainer and a maxillary removable retainer (traditional Hawley-type) at the end of active treatment for 2 to 3 years. The other 97 patients (20 males; 77 females) were placed in maxillary and mandibular removable retainers (traditional Hawleytype) for the same period of time. The two-fold purpose of this study was to: a) identify whether the type of retention—either Hawley retainers or Hawleys in combination with a fixed lingual retainer—provided greater long-term stability and b) review and document the long-term posttreatment changes of orthodontic cases. Treatment records were made at the start of treatment, at the end of active treatment, and at a long-term recall examination. The average long-term recall period for these patients is 16 years out of the active phase of treatment (13.5 years postretention). Major findings were: Temporary use (~ 2.5 years) of a mandibular fixed retainer following comprehensive orthodontic treatment appears to add little to long-term stability; therefore, if fixed retention is considered for retention, it should remain indefinitely to ensure stability. The amount of relapse seen in both groups was quite small, and the clinical difference between groups at the long term (average ~ 0.6 mm) was even smaller. Mandibular intercanine width was slightly expanded during treatment, but by the long-term recall examination, this dimension had returned to its pretreatment value. The maxillary and mandibular arches both became slightly narrower after treatment as measured by intermolar width and intercanine width. Overjet and overbite both increased after treatment. 131
About two-thirds (64%) of the correction of mandibular Incisor Irregularity was maintained over the long-term period. The mandibular Incisor Irregularity at the recall examination was less than 3.5 mm in 73% of cases, which is the limit suggested by Little (1975) as being clinically acceptable. There is a significant statistical association between the amount of change during treatment and the amount of relapse. Prediction of the amount of relapse from the treatment change takes the form of Y = 1.26 – 0.13(X) for the 166 cases in this study, meaning that a 1.0 mm change in Incisor Irregularity is associated with 0.13 mm of relapse. These results (~ 2.2 mm Incisor Irregularity at long-term recall) seem more stable than those reported in most long-term recall studies. It is likely that posttreatment changes and retention protocols will continue to cause discussion among the orthodontic community. Both groups of patients in this study treated under the Tweed guidelines remained extremely stable regardless of which retention protocol was used. However, patients must be conditioned to the potential occlusal changes that could occur, and it must be impressed on them the importance of their diligence in maintaining the stability of their dentition as they age. Further research should be done to determine if these same results could be expected for other treatment philosophies that do not observe such strict treatment parameters, i.e., upright mandibular incisors, minimal if any lower intercanine expansion, and the like. 132
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EFFICACY OF TEMPORARY FIXED RETENTI
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DEDICATION This thesis is dedicated
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ABSTRACT Instability of the occlusi
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CHAPTER 5. DISCUSSION .............
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LIST OF FIGURES Figure 3-1. All cas
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Figure 4-14. Box plot of the distri
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Joondeph and Riedel (1994, p 908) d
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Strang (1952, p 794) claimed that
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malocclusion must be maintained if
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e aimed at maintaining, in most ins
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three time intervals: during treatm
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mechanical treatment does not neces
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elation, the masticatory system wil
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exerted on the denture from the buc
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In summary, the variance in tongue
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Sinclair and Little (1983, p 114) a
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Study and 43 orthodontically treate
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and Sakols 1982; Vaden et al. 1997;
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years postretention. Årtun et al.
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adjustment, if necessary. This abil
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Duration of Retention The premise i
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The reduction in tooth structure of
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4. The most stable position of the
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CHAPTER 3. MATERIALS AND METHODS Sa
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The present sample consisted of the
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Figure 3-2. Illustration of how mol
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Figure 3-3. Illustration showing di
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Figure 3-5. Illustration showing mi
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Figure 3-6. Illustration showing an
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Figure 3-8. Illustration showing in
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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
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
Page 95 and 96: larger ANB at the recall examinatio
Page 97 and 98: 21 19 Total Chin (mm) 17 15 13 11 9
Page 99 and 100: Figure 4-8. Box plot of the distrib
Page 101 and 102: which a Class I relationship was no
Page 103 and 104: Figure 4-11. Plot of mean Curve of
Page 105 and 106: Figure 4-13. Box plot of the distri
Page 107 and 108: Table A-4 addresses the question of
Page 109 and 110: Figure 4-16. Bar chart of the avera
Page 111 and 112: only sample changed significantly m
Page 113 and 114: 3 2 1 0 Canonical Variate 2 -1 -2 R
Page 115 and 116: 8 Anterior Discrepancy (ADisc) 6 4
Page 117 and 118: 40 Incisor Aspect Ratio (IAR) 30 20
Page 119 and 120: 1.5 Incisor Segment Depth (ISD) 1 0
Page 121 and 122: more stable (i.e., the mean change
Page 123 and 124: Molar Correction (MC) 10 8 6 4 2 0
Page 125 and 126: Anterior Segment Width (ASW) 1 0 -1
Page 127 and 128: final vertical positions. This phas
Page 129 and 130: decreased in both arches during the
Page 131 and 132: Figure 5-1. Plot of average Incisor
Page 133 and 134: Based on the present results, the u
Page 135 and 136: these variables indicate more anter
Page 137 and 138: and the hassle associated with plac
Page 139 and 140: Figure 5-2. Scatter-plot graph refl
Page 141: stability?” and “for how long?
Page 145 and 146: Baume LJ, Horowitz HS, Summers CJ,
Page 147 and 148: Case CS. Techniques and principles
Page 149 and 150: Glenn G, Sinclair PM, Alexander RG.
Page 151 and 152: Joondeph DR. Retention and relapse.
Page 153 and 154: Littlewood SJ, Millett DT, Doubleda
Page 155 and 156: Ormiston JP, Huang GJ, Little RM, D
Page 157 and 158: Rosenstein SW, Jacobson BN. Retenti
Page 159 and 160: Steadman SR. A philosophy and pract
Page 161 and 162: Zachrisson BU, Büyükyilmaz T. Bon
Page 163 and 164: Table A-1. Descriptive statistics a
Page 165 and 166: Table A-2. Descriptive statistics a
Page 167 and 168: Table A-3. Descriptive statistics f
Page 173 and 174: APPENDIX B. ANCOVA TESTS OF THE COM
Page 175 and 176: Table B-1. Continued. Sex Retention
Page 185 and 186: Table C-1. Results of ANCOVA tests
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Table C-25. Results of ANCOVA tests
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Table C-31. 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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