Influence of molar support loss on stress and strain in premolar periodontium: a patient-specific FEM study.

Objectives: To test the hypothesis that loss of molar support causes increased stress and strain in the periodontal structures surrounding the premolars, and to assess the influence of denture use on stress distribution.
Methods: Subjects included female patients with unilateral and bilateral loss of mandibular molar teeth and controls with complete dentition (n=7 in each group). The subjects included had normal dentition mesial to the edentulous region and use of a lower free-end saddle removable partial denture. Occlusal contacts were registered in vivo, and a patient-specific finite element model was constructed for each subject based on morphological measurements of the diagnostic cast and radiographs. The maximum bite force on each tooth was then used to calculate the stress and strain on the cortical and the cancellous bone.
Results: Mean maximum bite force and maximum principal stress and strain on periodontal tissues of the second premolars were significantly higher in the bilateral molar loss group than those in the other groups (p<0.05). The increase in stress could not be prevented by wearing dentures. The mean maximum stress and strain per bite force were relatively constant among the groups, indicating that the increased maximum stress and strain in the bilateral molar loss group was attributed to the higher maximum bite force.
Conclusions: The results suggest that the periodontium surrounding the most posteriorly located occluding premolars may become sensitive to bilateral loss of molar support when patients exhibit higher maximum bite forces.