Effect of PDL elastic modulus on biomechanical behavior of mandible

Objectives: Previously, we reported the biomechanics of mandibular torus development in response to lateral load acting on teeth using a 3-D finite element (FE) model, consisting of the dentition, periodontal ligament (PDL), and mandible. However, it was difficult to quantify the mechanical properties of PDL in the FE model. In the present study, we investigated the effect of PDL elastic modulus on the biomechanical behavior of the mandible. Methods: Three FE models were constructed with PDL at a thickness of 0, 0.2 or 0.4 mm in two premolars and first molar on both sides. The PDL elastic modulus was estimated to be 1 or 10 MPa. A load of 100 N was applied on the buccal cusp of the second premolar in two directions; one tilting to the buccal side and the other along the tooth axis. The Von Mises stress was calculated on both the lingual surface and alveolar bone of the mandible. Results: Under lateral loading, the no-PDL model produced higher stress on the lingual surface near the apical region of the loaded tooth and the lingual crest of the alveolar bone. When the PDL elastic modulus decreased, the peak stress not only increased, but also appeared on the buccal crest and apical third of the alveolar bone. Under axial loading, the no-PDL model showed stress concentration on the lingual side of the crest. When the PDL elastic modulus decreased, the stress concentration diminished, and stress became more apparent in the apical area. Conclusion: Within the limitations of the present study, it is concluded that application of lateral loading in a PDL model with lower elastic modulus causes stress on the lingual surface of the mandible, as well as on the crest and apical third of the alveolar bone.