Effects of Edentulism on the Structure of the Human Mandible

Open Access
Author:
Doberstein, Andrew Michael
Area of Honors:
Biology
Degree:
Bachelor of Science
Document Type:
Thesis
Thesis Supervisors:
  • Timothy Michael Ryan, Thesis Supervisor
  • Stephen Wade Schaeffer, Honors Advisor
Keywords:
  • Edentulation
  • Geometric Morphometrics
  • Mandible
  • Landmarking
  • Tooth loss
Abstract:
The bones in the human body are constantly remodeled as osteoclasts and osteoblasts remove and add bone in order to adjust to changing mechanical conditions. Much research has been done with respect to how our diet, the way in which we exercise, and our genetics influence skeletal morphology and its responsiveness to external environmental conditions. This study seeks to determine the effects of tooth loss on the shape of the mandible. Specifically, I seek to understand how the structure of the human mandible is altered as a result of the progressive loss of teeth during life in order to better understand the role of changing mechanical forces on mandibular shape. I predicted that tooth loss would be reflected in the shape of the mandible. I expected that tooth loss would explain structural variation particular to the alveolar crest and the mandibular corpus. I tested the null hypothesis that edentulation, or tooth loss, along with age and sex do not have any effect on the structure of the human mandible. A sample of 30 human mandibles were digitized and landmarked with the intent to use geometric morphometrics to identify structural variation among each mandible in the observed population. The morphometric data were used to assess shape variation in relation to the degree of edentulism, age, and sex. The data collected through this study suggest that edentulation does contribute to changes in mandibular shape. Specifically, the loss of teeth leads to a widening of the mandibular corpus to form more of a “U-shape” as opposed to a more “V-like-shape” present in individuals with teeth. Additionally, tooth loss results in considerable alveolar ridge resorption and an increase in the gonial angle. Age and sex also correlate significantly with changes in mandibular structure, as older female individuals tended to be prone to the same mandibular restructuring observed in edentulous mandibles. The reason for this is not certain. This study identifies the structural changes that occur upon tooth loss in the hopes that future research will be done to preserve the integrity of the mandible for edentulous patients, while improving the lives of millions.