Research: Class of 2000

Cosse, C.C. "Class II Treatment Modalities and Airway Evaluation," Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


The research objective of this study was to obtain a representative sample of current treatment modalities for Class II correction used by practicing orthodontists in Oregon and Washington. Practitioners' beliefs concerning airway and its contribution to facial disharmony and practitioners' role in recommendation/referral to an ear, nose, and throat specialist were also examined. Finally, results were analyzed for differences based on location and experience. Methodology entailed sending surveys to 341 practicing orthodontists in Oregon and Washington to obtain information on preferred Class II treatment modalities in children and adults, as well as to investigate the role of airway and the practitioner's use of an airway examination. Of the 242 surveys returned, the data indicated that when treating Class II malocclusions in adults, practitioners predominantly elect extraction as the treatment of choice, followed by elastics alone. This was consistent in both states. Among these practitioners, the treatment modality of choice for Class II correction in children was headgear, followed to a lesser extent by elastics alone, extractions, and finally the Herbst appliance. On average, more than 60% of respondents said they evaluate airway routinely and would likely recommend tonsillectomy and/or adenoidectomy. Oregon orthodontists were more likely to routinely evaluate airway than were Washington orthodontists. This discrepancy increased as the years in practice increased. Washington practitioners, on the other hand, were more likely to refer for tonsillectomy/adenoidectomy than were Oregon respondents, although this number leveled out as experience increased.  

Datwyler, D.R. "Evaluation of Orthodontically Treated Profiles," Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


The purpose of this study was to determine whether trained orthodontists can actually identify cases that were treated with extraction of four first premolars and those that were treated by nonextraction therapy. It was hypothesized that one cannot accurately determine the type of treatment a patient received simply by looking at photographs of the treated patient. To examine the feasibility of this hypothesis, forty cases were selected at random from the archives of the Department of Orthodontics at Oregon Health & Science University. As the desire was to select cases that might be considered "borderline" extraction cases, selection criteria necessitated that the patients be youth (no adults) and present for initial treatment with (1) Class I molar relationship, (2) Moderate crowding (3.0 to 8.0 mm) in one or both arches, and (3) Adequate pre- and post-treatment records, including profile photographs. A total of 17 orthodontic evaluators (comprising 8 OHSU Orthodontic faculty members and 9 residents) and 10 lay persons took the profile evaluation test. The results of this study reflected similar studies which found extraction profiles to be pleasing and nonextraction treatment to have little effect on the profile. This indicates that extraction therapy in orthodontics most often produces either undetectable or better esthetic profile outcomes. The results further indicated that even trained orthodontists cannot easily determine the mode of orthodontic treatment when observing before and after profile photographs.  

Guyette, A.L. "Comparison of Post-Treatment Occlusal Settling Utilizing Hawley Versus Circumferential Maxillary Retainers." Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


This study examined the settling capabilities of circumferential maxillary versus Hawley retainers. Due to the lack of occlusal interferences in retainer design, it was hypothesized that circumferential maxillary retainers would offer better post-treatment settling of the occlusion than that experienced through the use of Hawley retainers. It was anticipated that proof of this hypothesis would be found in a greater number of post-treatment occlusal contacts over time in the circumferential retainer group of subjects. Methodology entailed alternately prescribing circumferential maxillary or Hawley maxillary retainers--in conjunction with a mandibular bonded canine to canine retainer--to 32 consecutive patients at the Oregon Health & Science University School of Dentistry. Although the data indicated greater increases in contacts for the circumferential retainer group over the retention period, as well as a possible trend toward greater settling capability of the circumferential retainer, the results were not statistically significant. Thus it was concluded that there are no statistically significant differences between the Hawley versus circumferential retainer designs for the maxillary arch. In order to more conclusively determine the settling capabilities of circumferential versus Hawley retainers, further evaluation of a larger sample over a greater period of time is required.  

Kim, O.K. "CSMI: Cervical Skeletal Maturity Index, CSMI with % Growth Remaining of Facial Bone," Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


CSMI was developed to predict the percent growth remaining of the mandible and maxilla. CSMI is a ratio between anterior intervertebral space of C2-3 and vertical height of cervical body of C3. CSMI shows a gradual decrease exponentially along the chronologic age by decrease of intervertebral space and mainly increase of vertical body height. Vertebral ring affects the shape of vertebral body, accentuating the concavity of the upper and lower surface of the vertebral body. CSMI and percent growth remaining of mandible and maxilla show a linear correlation as with Fishman's SMI. CSMI is a better predictor for percent growth remaining than chronologic age, but less predictive than SMI. However, CSMI may be a very useful predictor for the percent growth of the mandible and maxilla in that it eliminates additional hand wrist x-ray and is applicable to every patient who has a cephalogram.  

Sierk, C.R. "Soft Tissue Profile Changes in Patients Treated With and Without the Extraction of Four First Premolars," Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


The purpose of this retrospective study was to describe the effects of extraction versus non-extraction treatment on six common measures of the lip soft tissue profile. Fifty patients had received treatment, including the extraction of four first premolars, and fifty had received treatment without extraction. The data were broken down into subgroups comparing results obtained between individuals presenting with Class I and Class II, div 1 malocclusions, as well as between males and females. Pre-treatment, post-treatment, and treatment change means were analyzed with standard t-tests for statistical significance. The findings revealed changes in the soft tissue profile that were in the direction of published norms for both the extraction and non-extraction patients. The extraction or non-extraction decision affected the soft tissue profile--most notably in males and most likely in lower lip retrusion.  

Tremblay, B.D. "An Analysis of Treatment Results in Class I Finished and Class II Finished Cases Using the PAR Index," Orthodontic Certificate Thesis, Oregon Health & Science University, June 2000.


The Peer Assessment Rating (PAR) Index is a British-developed occulsal index that measures the severity of dental malocclusion. Using a series of 11 measurements, the score provides an estimate of how far a case deviates from normal alignment and occlusion. It can also be used as an objective measure in evaluating the effectiveness of orthodontic treatment. Orthodontic treatment sometimes involves the extraction of permanent teeth. The most common extraction pattern involves the extraction of four premolar teeth. Those cases are finished in a Class I molar relationship. Occasionally a situation calls for the extraction of only two upper premolar teeth. These cases are finished in a Class II molar relationship. There has been some controversy as to the functional occlusal quality of cases that are finished in a Class II molar relationship. This investigation sought to analyze the quality of Class II finished cases (treated with upper premolar extractions only) compared to Class I finished cases (treated with four premolar extractions). Thirty cases of each were selected from the orthodontic clinic at Oregon Health Sciences University and the PAR Index was applied to pre- and post-treatment records. Results using the PAR analysis indicated that cases treated with the extraction of four premolars started with higher PAR scores and finished with lower PAR scores than cases treated with the extraction of two upper premolars. Possible reasons for the higher PAR score found in cases treated to Class II may be overcorrection of the Class II molar relationship, failure to close all extraction spaces, failure to adjust the mesio-lingual cusp of the upper first molar, and poor second molar occlusion.