Date of Degree
MS (Master of Science)
Thomas E. Southard
Introduction: Individuals with short lower anterior facial height (LAFH), reduced mandibular plane angle, and excessive overbite resulting from upward and forward mandibular rotation are traditionally classified as skeletal deep bites. Our purpose was to explore phenotypic variation within short LAFH individuals using geometric morphometric methods. Methods: Cephalograms of 101 individuals (64 female, 37 male; age range: 7-62 years) with LAFH to total anterior facial height (TAFH), ratio (LAFH/TAFH), at or below 52.6% were studied. Principal component analysis, cluster analysis, and canonical variate analysis captured phenotypic variation and identified homogenous groups. Results: Four principal components were identified which accounted for 49% of the variation within the skeletal vertical and sagittal dimensions, flexure of the gonial angle, and incisor angulation. Cluster analysis resulted in 3 discrete short LAFH subpenotypes. Conclusions: Within the selected population of short LAFH individuals, we found: A range of morphologic variation. Convergent and divergent facial patterns with concomitant variation in gonial angle and ramus height. Anteriorly directed condylar morphology correlated with characteristics of extreme forward mandibular rotation; less anteriorly directed condylar morphology correlated with characteristics of backward mandibular rotation. Overbite magnitude is independent of vertical skeletal relationship and/or characteristics of forward mandibular rotation.
The term short lower anterior face height is one used to describe individuals with a shorter dimension of their face as measured vertically between the base of the nose and the chin. This facial pattern can make certain aspects of straightening the teeth and achieving an attractive smile using braces somewhat more difficult depending on the individual. There are not currently many scientific studies about facial patterns found within people sharing the trait of a short lower face. The purpose of this study was to explore possible different characteristics that might differentiate people with short face heights and see how these differences may help orthodontists achieve esthetic results during and after treatment with braces. We did this by finding the same 28 points on x-rays of 101 people using a method called geometric morphometrics. The results tell us that even within a group of people who should be similar (all of them having short lower face height), we see a lot of differences. These findings enable orthodontists to make more accurate diagnoses of their patients, ideally resulting in a better, more individualized plan for the orthodontic care of each patient.
vii, 38 pages
Includes bibliographical references (pages 35-38).
Copyright 2015 Julie Marie Wees