EFFICACY OF TEMPORARY FIXED RETENTION FOLLOWING ...

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CHAPTER 5. DISCUSSION Relapse—a return towards pretreatment conditions—seems to plague most orthodontic cases to some degree. Similar to the aging process, it is difficult to predict the extent to which an individual case will relapse. On more than one occasion, Gerald Samson (personal communication, February 2009; May, 2010) has said that “As the process of aging progresses, the skin wrinkles and so do teeth.” Put another way, “The dentition constantly changes throughout life” (Horowitz and Hixon 1969, p 3). To stop orthodontic relapse is akin to stopping the aging process. Because posttreatment relapse occurs to some degree in all patients, evaluations of the efficacy and rationale of various methods aimed at prevention are valuable. Lysle Johnston (1993) has asserted that orthodontic treatment may be more stable than had previously been documented. He challenged the specialty to produce other samples and treatments to be subjected to long-term scrutiny. To date, the vast majority of research concerning long-term stability has come from the Department of Orthodontics at the University of Washington (reviewed in Little and Sinclair 2009). The present research intends to provide additional insight into the long-term stability of treated patients. The nature of the present sample (Harris 1985) is that (a) cases are evaluated long-term (≥ 10 years after debanding), (b) cases were treated in private practice, and (c) all cases were treated using standard edgewise mechanics (Sandusky and Gramling 1988). The two-fold intent of this study was to determine whether the type of retention—either Hawley retainers alone or Hawleys in combination with a fixed lingual retainer—provided greater long-term stability, and to compare the findings of this study to other long-term outcomes. This was a cast analysis where records were gathered before (T1), after (T2), and at least 10 years (T3) following the active phase of orthodontic treatment. A strength of this study is the large sample size of 166 patients, of whom 69 received a maxillary Hawley retainer in combination with either a fixed mandibular canine-to-canine or first premolar to first premolar retainer, and the other 97 received maxillary and mandibular Hawley retainers. Mandibular fixed retainers were removed on average 2 to 3 years after the end of treatment, after which no mandibular retention was used, and the duration of maxillary retainer wear was left up to the discretion of the patient. Retention is the phase of orthodontic treatment that attempts to keep teeth in their corrected positions following active tooth movement with orthodontic braces (Littlewood et al. 2006). The intent of Hawley retainers is to hold the teeth in their end-of-treatment positions yet allowing them to passively settle into their 115
final vertical positions. This phase requires substantial patient compliance. The intent of fixed retention is to maintain an ever-present rigid control, particularly over the lower incisors, that does not depend on patient compliance. The idea is that, if fixed retention remains in place for a couple of years, this allows the periodontal tissues to become reoriented and passive to the new tooth positions and provide stability to incisors during the period of time when most relapse is thought to occur (Reitan 1967; Melrose and Millett 1998; Al Yami et al. 1999). Prolonged fixed retention for a couple of years might also allow fixation of the incisors until issues of the third molars have been addressed (Bergstrom and Jensen 1960; Sheneman 1969). Sample Considerations The cases used for the present study represent a geographically diverse sample consisting of records collected from several orthodontic practices in the United States and Mexico. As noted, all cases were treated with a similar treatment philosophy. Possible shortcomings of this study might be associated with the fact that all of the records were voluntarily submitted by orthodontists in private practice. This collection strategy could allow the orthodontists to cherrypick their cases and submit cases that they perceived to retain more satisfactory results. However, this risk is no greater or worse than any other recall study of this type. We have to rely on the desire and intent of the original data collection of the International Tweed Foundation, which expressly requested doctors to submit cases of all quality to allow for a representative sample of all treatment outcomes. There is no reason to believe this request was not adhered to. In addition, the overall scarcity of 10 year post-treatment records tends to minimize this bias, because in most cases, you are lucky to “get what you can get.” An example of this was documented in the sample protocol of two studies out of St. Louis (Paquette et al. 1992; Luppanapornlarp and Johnston 1993). Efforts were made to contact each prospective patient five times. Out of 2,500 prospective patients, only 125 actually participated in the two studies. This recruitment rate of 5% illustrates the difficulty of obtaining long-term samples. There also is the insurmountable issue of self-selection. It seems likely that patients with stable (and, thus, esthetic) outcomes would be more willing to participate in a recall study. Conversely, subjects who were non-cooperative patients and/or had unstable outcomes might be less enthusiastic about being reevaluated by their orthodontists since this could leave them open to criticism by the specialist. Another issue that is difficult to control is the individual orthodontist’s commitment to the use of a fixed retainer. Despite the consensus opinion that 116
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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
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
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: Anterior Segment Width (ASW) 1 0 -1
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 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-2. 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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