EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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It is difficult to draw firm conclusions as to why total chin shows up as a statistically significant predictive variable at the pretreatment stage and again at posttreatment based on the results of the present study. The greater total chin dimension that persisted from the pretreatment stage to posttreatment stage in the fixed retention group was associated with more anteriorly positioned mandibular incisors at both treatment stages, as evidenced by greater IMPA and incisor depth. Many clinicians today consider fixed retention in the treatment planning phase when severe pretreatment Incisor Irregularity is present. In the present study, there was no statistical difference in Incisor Irregularity prior to treatment (5.4 mm in the fixed group versus 5.9 mm in the removable group). However, by the end of treatment, Incisor Irregularity was significantly greater in the group (0.5 mm versus 0.2 mm) in which a fixed retainer was used. Greater Incisor Irregularity at the end of treatment seems to have added to a sense of incomplete orthodontic correction and greater risk for future instability. A deeper Curve of Spee persisted in the fixed retention group following treatment (0.8 mm versus 0.4 mm), albeit small, and this was identified as a significant predictor in the multivariate statistical analysis. Incomplete leveling of the Curve of Spee seems to have influenced the decision in favor of using fixed retention. Yet when evaluating the amount of change in the Curve of Spee during the recall period, the removable group displayed a slightly greater relapse (0.6 mm versus 0.4 mm), revealing that fixed incisor retention added little to maintaining the Curve of Spee correction. Along this same line, lack of molar correction during treatment (where a Class I molar relationship was not fully achieved) was greater in the fixed retention group (1.5 mm versus 1.0 mm). This difference was statistically significant when evaluated univariately (Table A-2), and could have been the result of the decreased mandibular incisor uprighting also seen in this group. Considered together, there was a deeper Curve of Spee and greater molar relationship during treatment in the removable group than in the fixed retention group. This suggests that fixed retention could have been considered following treatment if there was a sense of incomplete correction or an inability to achieve the desired degree of orthodontic correction. Clinical Relevance Our perception is that the use of temporary fixed retention following orthodontic treatment has largely been abandoned. This is predominately because of concerns over maintenance responsibility, periodontal health, caries 125
and the hassle associated with placing the appliance following treatment. Results of the present study document that long-term stability is clinically no greater in patients retained by fixed retention for a short time following active treatment (ca. 2 years) than patients receiving removable retention alone. Therefore, when weighing the advantages versus disadvantages of placing a fixed lower retainer (time, money, trouble, maintenance, etc.), it seems that the fixed retainer has little clinical advantage if only placed temporarily, and that if a fixed retainer is to be used, it should be planned to remain in place indefinitely. Furthermore, studies have established that relapse occurs to some degree in combination with the normal aging process in most every patient, and that retention to some degree is needed following orthodontic treatment (Sillman 1964; Lundström 1969; Little et al. 1981, 1988; Behrents 1985a, 1985b, 1989; Al Yami 1999; Harris et al. 1999; Richardson 1999; Stephens et al. 2005). What continues to be debated is the broad question of why this relapse occurs and to what extent it will occur in individual patients. Currently, it seems the majority of fixed retainers, when placed, are anticipated to be left indefinitely. Littlewood et al. (2006) concluded that there is insufficient research on which to base clinical judgments. From their conclusions and based on the research presented here, it can be inferred that no current mode of retention is superior to another. One caveat to this conclusion is the individualized variability in growth changes that takes place in postorthodontic patients. Growth studies by Behrents (1985, 1986a, 1986b), Nanda (1971, 1990) and Harris et al. (1994, 1997) have documented the variability in craniofacial growth changes among individuals. These changes do not stop in young adulthood, but continue throughout life. It was probably on this premise that Riedel (1960) contended that all patients must be thoroughly evaluated to determine what type, if any, and for how long retention procedures should be undertaken. Interestingly, Nanda and Nanda (1992) proposed that retention devices should be differentially selected on the basis of dentofacial morphology and the anticipated magnitude and directions of growth instead of simply using the clinician’s retainer of choice for all cases. Nanda and Nanda (1992) stress the importance of maintaining “active” retention through the pubertal growth spurt until maxillomandibular growth is completed, and they assert that the clinician has to be alert to the growth pattern of each individual patient. Specific examples of customized retention cited by the authors include a) continued use of a high-pull headgear in long-face syndrome patients during the retention phase, b) addition of an anterior biteplane to the retaining device in short-face syndrome patients, and c) longer retention periods for patients experiencing a delayed pubertal growth spurt, i.e. patients with skeletal deep bite. 126
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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,
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
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: these variables indicate more anter
Page 139 and 140: Figure 5-2. Scatter-plot graph refl
Page 141 and 142: stability?” and “for how long?
Page 143 and 144: About two-thirds (64%) of the corre
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-7. 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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