The effect of inclination of the maxillary central incisor and the M/F ratio on the tooth movement, periodontal stress and strain : finite element method

Abstract

The purpose of this study was to determine the effect of inclination of a maxillary central incisor and the moment to force ratio on anteroposterior and vertical movement and periodontal stress and strain by using the finite element method (FEM). Five 3D models of a right maxillary central incisor were constructed based on average anatomical dimensions with 0, 10, 20, 30, and 40 -degree inclination. A constant lingual force of 1 N at 4.5 mm apical to the incisal edge and the moment varied from 8 to 9, 10, 11, and 12 N-mm were applied to each model. Anteroposterior movement of the incisal edge and apex and vertical movement of incisal edge were measured. Periodontal stress and strain were expressed as the areas and magnitude of the highest maximum principal stress and strain and also the lowest minimum principal stress and strain. The results showed that with increasing inclination and the moment to force ratio, the incisal edge tended to move labioapically and the apex tended to move lingually. Moreover, with increased inclination, the moment to force ratio which produced bodily movement decreased but the location of the center of resistance of a maxillary central incisor was relatively constant in terms of the proportion of vertical distance to the root length from the apex, which was approximately 0.67. In bodily movement, the area of maximum compressive stress and strain changed from mid root area in 0° inclination to apical area in 40° inclination; while the area of maximum tensile stress changed from mid root area to cervical area but the area of maximum tensile strain was still in the mid root area. With increased inclination, magnitude of maximum compressive stress and strain and tensile strain increased but maximum tensile stress decreased.