EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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Table 5-1. Summary of prior studies that investigated the long-term stability of orthodontic treatment for mandibular Incisor Irregularity (II). Research (1) (2) (3) (4) (5) (6) (7) (8) (9) (10) (11) Year 1981 1982 1987 1988 1989 1992 1993 1994 1996 2003 2010 Sample Size (n) 65 96 28 31 30 63 62 22 78 32 166 Mean Postretention 13 20 # 8 10 14 15 15 6.3 14 12 13.5 Range Postretention 10-24 12-35 # 3- na 10-22 9-20 11-23 5-17 9-33 5-22 8-44 Start of Treatment Mean Age (yrs) 13† na 13 13 † 13 † 13 13 11 11 13 13 † Mean II (mm) 7.3 8.2 2.9 7.4 2.5 5.8 5.1 5.2 4.1 8.1 5.7 SD II (mm) 4.3 3.2 1.4 na na na na 4.2 3.0 na 3.9 End of Treatment Mean Age (yrs) 15 † na 15 16 † 15 † 14 15 na na 15.5 † 15.8 † Mean II (mm) 1.7 na 1.0 1.7 1.5 0.6 0.6 1.0 1.0 1.8 0.4 SD II (mm) 0.6 na 0.5 na na na na 0.8 0.8 0.9 0.6 Recall Examination Mean Age (yrs) 30 † na 27 30 † 32 † 29 30 na 31 31.6 † 32.2 † Mean II (mm) 4.6 2.8 2.2 5.3 3.8 3.2 3.5 2.4 3.8 2.6 2.2 SD II (mm) 1.9 2.7 1.7 na na na na 1.7 2.0 1.2 2.3 Studies: (1) Little et al. 1981 (5) Little and Riedel 1989 (9) Årtun et al. 1996 (2) Sadowsky and Sakols 1982 (6) Paquette et al. 1992 (10) Boley et al. 2003 (3) Glenn et al. 1987 (7) Luppanapornlarp and Johnston 1993 (11) Present study 2010 (4) Little et al. 1988 (8) Sadowsky et al. 1994 † median; # posttreatment; na = not applicable 121
Based on the present results, the use of temporary fixed retention (~ 2.5 years) following orthodontic treatment does allow for slightly less changes in Incisor Irregularity over the long-term. However, does this clinically inconsequential amount of change over the long-term (beyond 10 years) warrant the added time, expense, and hassle of placing a fixed retainer for such a transient time? We propose that if the time and effort is spent to use fixed retention at the end of treatment, plans for its indefinite use should be considered. Explanation for Stability Two important tenets of Tweed treatment mechanics (Sandusky and Gramling 1988) are to minimize mandibular canine expansion during treatment and to upright mandibular incisors over basal bone. In the majority of cases examined in the present study, both of these treatment goals were achieved. Expansion of the mandibular intercanine width was minimized during treatment. The average mandibular intercanine width for both retention groups prior to treatment was 24.5 mm. Following treatment, this dimension increased to 25.7 mm, resulting in an average in-treatment increase of just over 1.0 mm. Two cephalometric measurements, FMIA and IMPA, are used to evaluate the position of the mandibular incisors relative to the basal bone. The average FMIA for both retention groups prior to treatment was 60.2, and 62.5 at posttreatment, for an average intreatment change of 2.3. The average IMPA for both retention groups prior to treatment was 93.0 and posttreatment was 91.1, resulting in an average in-treatment reduction of 1.9. This is compelling evidence that the orthodontists in the present study recognized and attempted to (1) minimize the expansion of the dental arches because expansion of lower intercanine width is the most predictable of all orthodontic relapse (McCauley 1944; Tweed 1944; 1945; Riedel 1960; Steadman 1961; Lundström 1968; Bishara et al. 1973; Herberger 1981; Glenn et al. 1987; Bishara et al. 1989; Vaden, Harris, and Gardner 1997; Blake and Bibby 1998; Boley et al. 2003) and (2) maintain or upright the lower incisors because advancing the lower incisors is unstable and may seriously compromise posttreatment stability of the lower incisors (Lundström 1925; Tweed 1944; 1945; Riedel 1976; Shields et al. 1985; Houston and Edler 1990; Boley et al. 2003). The important influence that these two treatment goals have on the longterm stability of orthodontically treated cases is well documented by research referenced previously in the current study and in the final conclusions of Blake and Bibby (1998) in their review of the literature regarding retention and 122
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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
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
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: Figure 5-1. Plot of average Incisor
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 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
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Table B-5. 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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