Aim: The aim of this study is to establish a proportion between the inferior border of mandible and lower edge of the mental foramen and inferior border of mandible to occlusal plane for dentulous subjects and to evaluate the validity of this proportion in orienting the occlusal plane for edentulous subjects.
Materials and methods: The occlusal plane was evaluated in the selected 50 dentulous and edentulous subjects for its relation to the mental foramen and inferior border of the mandible. The orthopantograms obtained were traced with the markings and the measurements were tabulated under different headings. After measuring the distances, the proportion between the distances was determined. The mean proportions of dentulous, edentulous, male, and female subjects were evaluated. Then the proportion of male subjects was compared with that of female subjects and dentulous subjects with that of edentulous subjects. Comparison of proportion between the different groups was done by using unpaired t test. The mean and standard deviation (SD) were determined for each group separately and were compared within each group. From the calculated "t" value, "p" the probability for error was found out.
Results: In dentulous subjects, the proportion ranged from 1:3.53 to 1:4.40. The mean was 1:3.90. In edentulous subjects, the proportion ranged from 1:3.50 to 1:4.15. The mean was 1:3.84. On comparison, the difference between both the groups was 0.06. The difference was statistically insignificant (p = 0.14). In the comparison of dentulous male and female subjects, the difference obtained was 0.02. The difference was statistically insignificant (p = 0.77). The comparison of edentulous male and female subjects and the difference obtained was 0.03. The difference was statistically insignificant (p = 0.51).
Conclusion: The derived proportion of 1:4 between the inferior border of mandible and mental foramen and inferior border of mandible and occlusal plane in edentulous patients as measured on an orthopantogram may yield a plane of occlusion similar to that existing in the dentulous state.
Clinical significance: The above-drawn proportion between the inferior border of the mandible to the lower edge of the mental foramen and between the inferior border of the mandible and the occlusal plane in edentulous patients may yield a plane of occlusion which is oriented similar to that existing in the dentulous state. The proportions derived radiographically in this study can serve as a basis for future studies to establish the occlusal plane for edentulous subjects.
Keywords: Dentulous; Edentulous; Inferior border of mandible Occlusal plane..