Document Type


Date of Degree

Spring 2017

Access Restrictions

Access restricted until 07/13/2018

Degree Name

MS (Master of Science)

Degree In


First Advisor

Thomas E. Southard


Introduction: The purpose of this study was to evaluate the changes in marginal ridge alignment occurring through normal growth and development from early childhood to late adulthood and to examine if any statistical variation exists between males and females.

Methods: Dental casts of 38 subjects (15 females and 23 males) from the Iowa Growth Study were selected. The marginal ridge discrepancy was measured as the absolute value difference between adjacent marginal ridges of 20 interproximal contacts with both the ABO tool (data not shown) and a vertically mounted digital caliper. Upper and lower casts were tripoded to a level plane defined by the most posterior tooth and central point of the most erupted central incisor. A 15 subject calibration was used to measure inter-examiner reliability using the Cronbach’s Alpha and Kappa tests. The independent samples t test was used to examine the correlation of marginal ridge discrepancies between males and females.

Results: Cronbach alpha (p ≤ .001) and Kappa test (p ≤ .01) show excellent inter-rater reliability. The independent sample t test showed no statistical significance, with minimal exception, in marginal ridge discrepancies between males and females matched for age (p > .05). Group 1 showed significantly higher number of marginal ridge discrepancies within ABO range of 0 – 0.5 mm of males and females compared to Group 2.

Conclusion: Based on this study, no statistically significant differences were found in marginal ridge discrepancies between males and females. Also, the magnitude of marginal ridge discrepancies of erupting permanent teeth shows a decrease as an individual proceeds through growth and development and they remain relatively “level” during primary dentition.


American Board of Orthodontics, curve of Spee, marginal ridge, root angulation


vii, 37 pages


Includes bibliographical references (pages 36-37).


Copyright © 2017 Mason Andrew Dearing