Correlation of gonial angle size with cortical thickness, height of the mandibular residual body, and duration of edentulism.

STATEMENT OF PROBLEM: Previous reports on widening of the gonial angle in edentulous patients are conflicting. Aside from age and loss of teeth, other factors may influence change in gonial angle.

PURPOSE: This study evaluated gonial angles from panoramic radiographs of young and older dentate subjects and elderly edentulous subjects and investigated the relationship of gonial angle size to gender, age group, cortical thickness at the gonial angle, height of the mandibular residual body, and edentulous period in elderly edentulous subjects.

MATERIAL AND METHODS: A total of 356 panoramic radiographs of 3 groups of subjects were evaluated: the young dentate group, 131 subjects (mean age 27 years); the older dentate group, 97 subjects older than age 52 (mean age 64 years); and the elderly edentulous group, 128 subjects aged 76, 81, or 86 (mean age 80 years). The gonial angle, cortical thickness at gonial angle, and height of mandibular residual body were measured from panoramic radiographs made with the same radiographic equipment and selected according to criteria. A structured questionnaire was used to determine the history of edentulism. Paired and unpaired 2-tailed t tests served to test the difference in gonial angle measurements, and a linear regression was performed to study correlations (alpha=.05).

RESULTS: Difference in size of the gonial angle was found between dentate men and women (P<.05 in the young and P<.001 in the older dentate group), but not between elderly edentulous men and women. The elderly edentulous subjects had significantly larger gonial angles (128.4 degrees +/- 6.6) than did the young (122.4 degrees +/- 6.6, P<.001) and older dentate subjects (122.8 degrees +/- 6.6, P<.001). The angle size was negatively related to cortical thickness at the gonial angle only among 76-year-old edentulous women (P<.01), and was associated with average height of the mandibular residual body in the edentulous men and women (P<.01). No association existed between angle size and duration of edentulism. No differences were significant in any test of intraexaminer error.

CONCLUSION: In this study, elderly edentulous subjects had larger gonial angles than did dentate subjects. The angle size was correlated with low height of the mandibular residual body and with its cortical thickness in edentulous women.