Document Type

Thesis

Date of Degree

Spring 2014

Degree Name

MS (Master of Science)

Degree In

Orthodontics

First Advisor

Robert N. Staley

Abstract

Introduction: The purposes of this study were several. The first was to establish a mean value for the crown-to-root angle, or collum angle (CA), for maxillary central incisors in Class I normal occlusions. The second was to create a new crown-to-root angle based on anatomic points, the labial crown-root angle (LCRA), and correlate it with the CA for Class I normal occlusions and Class II division 2 malocclusions. Third, torque values were measured for maxillary central incisors using these anatomic points, and mean values were calculated for Class I normal occlusions and Class II division 2 malocclusions. Finally, mean values for CA and LCRA were analyzed for Class I normal occlusions and Class II division 2 malocclusions to detect differences between the two groups. Methods: 51 Class I normal samples and 42 Class II division 2 samples who met the inclusion criteria were studied cephalometrically. Relevant landmarks were placed, analyzed for reliability, and recorded for the measurements of interest. Results: The mean CA for Class I normal occlusions was not statistically different from zero (p= .0657). A strong increasing correlation between CA and LCRA was found for all samples (Pearson's correlation coefficient = 0.88, p < .0001). Mean torque values for Class I normal occlusions and Class II division 2 malocclusions were statistically different (3.95±10.85 degrees vs. 12.54±5.82 degrees, p < .0001). The mean CA for Class I normal occlusions and Class II division 2 malocclusions were statistically different (4.29±5.77 degrees vs. 1.78±3.94 degrees, p = .0178). The mean LCRA for Class I normal occlusions and Class II division 2 malocclusions were statistically different (31.60±4.24 degrees vs. 34.84±5.95 degrees, p = .00037). Conclusions: The mean CA in Class I normal occlusions is not statistically different from zero degrees. The LCRA is strongly correlated with the CA in both Class I normal occlusions and Class II division 2 malocclusions. The mean maxillary central incisor torque values for Class I normal occlusions is similar to that found in bracket prescriptions currently offered. Patients with Class II division 2 malocclusion exhibit statistically higher mean CA and LCRA values than patients with Class I ideal occlusion.

Keywords

collum angle, crown root angle

Pages

v, 50 pages

Bibliography

Includes bibliographical references (pages 49-50).

Copyright

Copyright 2014 Thomas John Bauer

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