Effect of occlusal hypofunction on centre of resistance in maxillary central incisor using the finite element method

Objectives: To determine differences in the location of centre of resistance (Cres) between functional and hypofunctional teeth and to evaluate the relationship between the pulp cavity volume and locations of the Cres, using the finite element (FE) method. Design: Retrospective cohort study. Participants: FE models of right maxillary central incisor, derived from cone-beam computed tomography (CBCT) images of 46 participants, were divided into normal function (n = 23) and hypofunction (n = 23) groups using anterior overbite and cephalometric measurements. Methods: Measurements of the tooth and pulp cavity volume were made from the CBCT. Cres levels were presented as percentages of the root length from the root’s apex. All data were analysed and compared using the independent t-test ( P < 0.05). The relationship between the location of Cres and volume ratios were evaluated statistically. Results: The means of the pulp cavity/tooth volume and root canal/ root volume ratio of the maxillary central incisor in the anterior open bite group were significantly greater than those in the normal group. The average location of Cres in the anterior open bite group was 0.6 mm (3.7%) apically from the normal group, measured from root apex. The difference was statistically significant ( P < 0.01). There was a significant correlation between root canal/root volume ratio and locations of Cres (r = −0.780, P < 0.001). Conclusions: The Cres in the hypofunctional group was located more apical than the functional group. As the pulp cavity volume increased, the level of Cres shifted apically.