Alignment of Biological Apatite Crystallites in Premolar and Molar Region in Cortical Bone of Human Dentate Mandible

Abstract

The mandible exists in a unique mechanical environment subjected to occlusal force and other functional pressures. In dentulous humans, differences in occlusal force and position are believed to be closely linked to the mandible's structural characteristics. The mechanical environment that this bone occupies is difficult to evaluate qualitatively, and it is therefore assessed indirectly by quantitative determination of bone mineral density (BMD). However, in order to understand the loading environment of the human mandible, we must also evaluate local bone quality. In the present study, we therefore sought to identify the structural properties of each tooth in the dentulous human mandible by qualitatively evaluating the crystalline orientation of biological apatite (BAp) as a marker of bone quality. After dividing the area from the alveolar ridge to the apical foramen surrounding the first and second premolar and molar regions of the Japanese dentulous mandible, we measured BAp crystalline orientation and BMD at a total of 4 sites including 2 on the buccal side and 2 on the lingual side. As a result, the orientation of BAp crystallites showed a significant difference between premolar and molar regions, namely preferred orientation in a direction vertical to the occlusal plane (Y-axis) was high for the premolar region and low for the molar region (p < 0.01). These findings indicated that quantitative evaluation of BAp crystallite orientations in the mandibular cortical bone has been revealed to be an effective parameter regarding the local loads that are applied to the human mandible. It was suggested that the distribution map of BAp crystallite orientations in the mandibular cortical bone based on this study would be valuable for planning the prosthodontic treatment in molar and/or premolar regions.

Analysis of the relevant factors associated with oral health-related quality of life in elderly denture wearers

“…Therefore, it is considered that there were no statistically significant differences in the number of PM and M between the two groups of subjects. Considering that the mandible of the first molar region has been reported to be an adequate mechanical environment, due to its stable macrostructure [37], it is reasonable to assume that the main occluding area on the denture base would still exist, even if the first molar is replaced by an artificial tooth, as long as the patient is provided with a denture fabricated by a dentist with specialized training in prosthodontics.…”