EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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teeth continue to change axial inclinations as the children continue to complete their growth to adulthood (Steadman 1967). These changes are rapid in childhood and early adolescence; by midadolescence, the pace has slowed but is still appreciable clinically; in adults, the astute clinical observer continues to detect changes, although they are of lesser degree and occur at a decreasing rate (Horowitz and Hixon 1969). Craniofacial growth changes are variable among individuals. These changes do not stop in young adulthood, but have been shown to be a continuous process that occurs throughout adulthood and have an effect on the craniofacial skeleton (Behrents 1985, 1986, 2008). In a landmark follow-up study to the Bolton Study, Behrents (1985) was able to recall approximately 200 orthodontically untreated participants ranging in age from the late teens into the 80s. These individuals had been previously examined as children and young adults in the Bolton Study from 1928 through the 1970s. This allowed for documentation of long-term longitudinal data in the form of cephalometric head films on orthodontically untreated individuals followed in some cases from early adolescence to their mid-80s. Behrents drew several conclusions about normal craniofacial growth in orthodontically untreated individuals. Behrents suggested that individuals experience significant “differential growth” within the craniofacial complex throughout adulthood due to increases in the size of their skeletal structures and changes in their shape. These changes in facial dimensions continue throughout adulthood, although less exuberantly than in adolescence (Behrents 1986). Overall, males grew more in later adulthood than females. The mandible increased in size in both sexes; however, in males, the mandible continue growth in a downward and forward direction, which produced a counterclockwise rotation of the mandible, while females exhibited more of a vertical change, causing the mandible to rotate in a clockwise direction. Maxillary incisors tended to upright in both males and females, while the mandibular incisors showed a consistent inclination in males, but a tendency for continued anterior inclination in females (Behrents 1986). Overbites did not change in either sex. Harris (1997) also documented the significant skeletodental changes found occurring in untreated individuals over time. Based on longitudinal data available for 60 untreated adults, arch widths were found to significantly increase over time, while arch lengths significantly decreased. This altering of arch dimensions can produce a significantly shorter-broader arch form over time. In contrast to previous studies (Behrents 1985b; Perera 1987), incisor overjet and overbite were found to remain constant. 19
Sinclair and Little (1983, p 114) assessed the dental casts of 65 untreated normal adolescents to determine “the nature and extent of the developmental maturation process of the normal dentition.” A normal occlusion was defined as occurring in untreated individuals with dental and skeletal Angle Class I relationships. The sample was obtained from records of children in the Burlington Growth Center Study, Ontario, Canada. Six variables (irregularity index as described by Little in 1975, mandibular intercanine width, mandibular intermolar width, mandibular arch length, overbite, and overjet) were evaluated in the mixed dentition (9 to 10 years), early permanent dentition (12 to 13 years), and early adulthood (19 to 20 years). The results showed decreases in arch length and intercanine width; minimal overall changes in intermolar width, overjet, and overbite; and increases in Incisor Irregularity. It was also noted that females exhibited more severe dental changes than males. More recently, Eslambolchi et al. (2008) documented the longitudinal dental changes in seen in 15 untreated children and 18 untreated adults who had been participants in the original Burlington Growth Research Project at the University of Toronto. In both groups, Little’s irregularity index continued to increase 2.0 to 4.0 mm with age, while intercanine and interpremolar widths continued to decrease. Arch length also decreased up to 2.0 mm in the children and 1.0 mm in the adults over time. Most orthodontic patients are treated in their adolescence, leaving ample opportunity for subsequent growth of the maxillary and mandibular complexes to move the teeth into unstable positions (Vaden, Harris and Gardner 1997; Gardner, Harris and Vaden 1998; Harris, Gardner and Vaden 1999). Conflicting reports exist in the literature as to the potential effects that continued craniofacial growth may have on incisor stability. Riedel (1960, p 187) admitted that, “Growth may be an aid in the correction of many types of orthodontic problems and it also may be of such character as to cause relapse of treated orthodontic patients.” Ricketts et al. (1972) reported that continued posttreatment growth may contribute to an increased pressure on the mandibular incisors as they are forced in a lingual direction with the advancement of the mandible. This occurs to a greater extent in patients whose incisors were tipped during treatment, as these teeth will have a greater tendency to be forced lingually. Similarly, Perera (1987) reported a relationship between mandibular growth and lower anterior crowding in untreated subjects (n = 29). Perera indicated that forward rotational growth in the mandible is closely related to lower incisor crowding that commonly occurs after the adolescent years. He suggested that as the mandible rotates forward, the lower incisors can become retroclined relative to the face. Similarly, Siatkowski (1974) conducted a longitudinal study that consisted of two 20
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: In summary, the variance in tongue
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
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
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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
Page 101 and 102:
which a Class I relationship was no
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Figure 4-11. Plot of mean Curve of
Page 105 and 106:
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,
Page 147 and 148:
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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Page 171 and 172:
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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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Page 179 and 180:
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Page 185 and 186:
Table C-1. Results of ANCOVA tests
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Table D-1. Descriptive statistics,
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Page 201 and 202:
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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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