Electronic Thesis and Dissertation Repository

Degree

Master of Clinical Science

Program

Orthodontics

Supervisor

Dr. Antonios Mamandras

Abstract

For proper orthodontic diagnosis and treatment planning, an accurate measurement of the relationship of the maxilla to the mandible in the sagittal plane is required. The ANB measurement has long been the gold standard for explaining this association. The purpose of this longitudinal study was to evaluate three linear measurements of the maxillomandibular anteroposterior relationship and determine which one best correlates with ANB. The constructed Frankfort horizontal-mandibular plane angle bisector (cFMAB-Wits), maxillomandibular bisector (MMB-Wits), and Frankfort-mandibular plane angle bisector (FMAB-Wits) were measured using a Wits’-type analysis and compared to ANB.

Pre-treatment (TO), immediate post-treatment (T1), and two years post-retention (T2) lateral cephalograms were analyzed for 121 Class I patients and 76 Class II Division 1 patients treated at the Graduate Orthodontics Clinic at the University of Western Ontario. 38 Class I and 30 Class II Division 1 untreated individuals from the Burlington Growth Centre served as controls. The data were evaluated using independent samples t-tests and one-way ANOVA to determine statistical differences between groups (p<0.05).

Each of the three linear measurements demonstrated modest correlation with ANB, regardless of presenting malocclusion. The difference in correlation with ANB between the three linear measurements was negligible. The cFMAB-Wits measurement produced a positive correlation with ANB, MMB-Wits, and FMAB-Wits. The Wits-type measurements all showed strong correlation amongst one another, suggesting their use may be interchangeable, but none can be used as a reliable surrogate for the gold standard ANB.

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