Abstract:

Objective This study aims to explore the influence of three-wall osseous defects on periodontal ligament stress under normal occlusal forces. Methods A finite element model for mandibular total dentition, periodontal ligament and alveolar bone was created based on cone beam computed tomography (CBCT) DICOM images. Mesial or distal proximal three-wall osseous defects at varying depths (namely, 1/3, 2/3 and 3/3 of the root) were simulated by modifying the elastic modulus of elements within the defects area. Occlusal forces with an angle of 45° to the long axis of the tooth were applied to the finite element model. In addition, the equivalent stresses of the periodontal ligament were analysed. Results In the case of no bone defect, the mean value of the periodontal ligament equivalent stress of 14 teeth was 5.71 MPa. The equivalent stresses of the periodontal ligament at different depths (namely, 1/3, 2/3 and 3/3 of the root) were 6.61, 7.14 and 7.42 MPa, respectively. With increasing depth of the osseous defects, stress on the periodontal ligament increased considerably, and the initial stress increment was greater than that of a later stage. Periodontal ligament stresses with mesial proximal three-wall osseous defects (at depths of 1/3, 2/3 and 3/3 of the root) were 6.62, 7.19 and 7.51 MPa respectively. Periodontal ligament stresses with distal proximal three-wall osseous defects (at depths of 1/3, 2/3 and 3/3 of the root) were 6.60, 7.10 and 7.33 MPa, respectively. For three-wall osseous defects located in the mesial surface and distal surface, a significant difference in periodontal ligament stress was lacking. In the case of the same absorption depth, the size relationship of periodontal liga-ment stress was in the following order: premolars>molars>incisors>canines. Conclusion Shallow three-wall osseous defects will likely cause a notable loss in strength of the periodontal ligament. Therefore, teeth with three-wall osseous defects should become the focus of clinical research. Treatment for these teeth should be administered as early as possible.

Key words: periodontal ligament, stress, vertical bone defects, three-wall osseous defects