Finite element analysis of the dental pulp under orthodontic forces

Introduction: To evaluate the stress at the apical third of the pulp and neurovascular bundle (NVB) during 5 types of orthodontic movement at different levels of bone loss. Furthermore, correlations among bone loss, orthodontic appliances, and stress increase were assessed. Methods: Based on cone-beam computed tomography datasets, 10 models of the mandibular second premolar were created. Each of these models was subjected to a gradual horizontal bone loss simulation (0-8 mm). Orthodontic forces of 20 g, 60 g, and 120 g were applied during the finite element analysis (FEA). For each bone loss level, stress values were evaluated with the use of Abaqus at the apical third of the pulp and the NVB. Results: The stress manifested at the apical third of the pulp was smaller than that at the NVB. The highest apical NVB stress was found for rotation (0.000546 N/mm(2) for 8 mm bone loss) whereas the lowest stress resulted after translational movements (2.35E-04 MPa for 8 mm bone loss). The FEA showed that Proffit's indicated orthodontic forces did not significantly disturb the pulpal blood flow and damage the apical NVB. Up to a doubling of the NVB stress, bone loss correlated with the force reduction to obtain similar stress levels compared with teeth with no bone loss. Conclusions: The present findings indicate that the stress manifested at the apical third of the pulp is smaller than that at NVB. Rotational movements induce the highest stress and translational forces develop the lowest stress related to the physiologic capillary blood pressure. Furthermore, in situations with reduced periodontium, lower forces are needed to reach the maximum tolerable stress compared with teeth with intact periodontium.