EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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stability in a new position.” Angle (1907) asserted that orthodontic corrections would remain stable if the teeth were placed in proper occlusion. Dental “occlusion” refers to how well the teeth are arranged individually and one-to-another within and between the dental arches (Harris and Corruccini 2008). “Proper” occlusion occurs when the mesiobuccal cusp of the maxillary first molar is positioned parasagitally in the buccal groove of the mandibular first molar (Angle 1899; Harris and Corruccini 2008). According to Angle, the achievement of this Class I molar relationship was a prerequisite in obtaining the proper interdigitation of the maxillary and mandibular cusp-fossa relationship. According to Huckaba (1952), Dewey and Anderson (1942) suggested that, in addition to the inclined plane relationship of opposing teeth, a proper cuspal guidance will serve as a natural aid to retention. According to Kaplan (1988, p 328), McCauley (1944) also stressed his opinion that the achieving of a proper canine relationship is the primary determinant of a functional occlusion and referred to the canine rise as a “protective mechanism for maintaining arch stability.” Occlusion is a dynamic balance of forces in which the maintenance of form is subject to functional requirements (Huckaba 1952). Tweed (1944) added further to the requirements of occlusion based upon the treatment results of some of his early cases. Based on the many patients he recalled years after treatment, Tweed concluded that there were several factors that must be achieved during treatment for a case to be deemed successful. These included a normal cusp and inclined plane relationship between opposing teeth; ideal axial orientations of all teeth; ideal relationship of the jaws to each other and to the skull; and, there must exist an ideal function of all masticatory elements involved. Tweed (1944) asserted that achievement of these objectives was dependent on the positioning of the mandibular incisor teeth over basal bone. Tweed (1945) claimed that the mandibular incisors should be treated to a 90 degree angle in relationship with the mandibular plane in order for incisor stability to occur. Strang (1949) suggested that the mandibular cuspid and mandibular first molar teeth are the key in determining the alignment pattern for the remaining teeth so that the dentition will be in harmonious balance with the muscular forces which constantly act upon it. Strang felt that if muscular balance was maintained in this manner, it should be possible to eliminate mechanical retention at the end of active treatment and-have a result that would remain stable. According to Lundström (1925), the presence of an adequate apical base is necessary for the correct positioning of the teeth in proper occlusion. He claimed that orthodontic experiments show that a normal occlusion attained by 11
mechanical treatment does not necessarily lead to the development of the apical base in harmony with the newly positioned teeth. This failure to attain bony support would lead to future instability. Lundström concluded that the apical base does not change to fit the occlusion, but that apical base dimensions dictated the establishment of a normal occlusion. Andrews (1972) observed the casts of 120 nonorthodontic patients in an effort to describe common characteristics that lead to the establishment of a normal occlusion. The patients were selected form the general public because they possessed a dentition that was well aligned and pleasing in appearance; a bite that looked generally correct, and no potential benefit from orthodontic treatment according to the author. From these nontreated patients, 6 common features or “keys” were found to be present. Andrews’ six keys to normal occlusion are: 1. Molar relationship. The distal surface of the distobuccal cusp of the maxillary firs molar contacts with the mesial surface of the mesiobuccal cusp of the mandibular second molar. 2. Crown angulation (tip). The gingival portion of the long axes of all crowns should be more distal than the incisal portion. 3. Crown inclination. The maxillary incisors should exhibit slight labial crown torque and all posterior teeth from the canine through the second molars should exhibit lingual crown inclination. 4. Rotations. All teeth should be free of undesirable rotations. 5. Tight contacts. The contact points between adjacent teeth should be tight and exhibit no spaces. 6. Occlusal plane. Occlusal planes should be treated such that they are flat or exhibit only a slight Curve of Spee. Andrews concluded that retention was not necessary in patients who possessed all six keys of occlusion, provided the third molars had been removed and growth had ceased. Harris and Behrents (1988) assessed the relative stability of the sagittal molar relationship in 61 orthodontically untreated persons with full dentitions who were recalled from the Bolton longitudinal study conducted in Cleveland, Ohio. The investigators found that 100% of the patients that originally presented 12
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: three time intervals: during treatm
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 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
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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
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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
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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
Page 131 and 132:
Figure 5-1. Plot of average Incisor
Page 133 and 134:
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
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.
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Littlewood SJ, Millett DT, Doubleda
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Ormiston JP, Huang GJ, Little RM, D
Page 157 and 158:
Rosenstein SW, Jacobson BN. Retenti
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Steadman SR. A philosophy and pract
Page 161 and 162:
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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Page 185 and 186:
Table C-1. Results of ANCOVA tests
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Page 193 and 194:
Page 195 and 196:
Page 197 and 198:
Table D-1. Descriptive statistics,
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Page 201 and 202:
Page 203 and 204:
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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