“Relative intrusion as a result of protrusion: A mathematical perspective”

Abstract

The aim of this study was to investigate the role of initial incisor axial inclination on the amount of bite opening, with the aid of trigonometry. The uncontrolled tipping movement of an upper central incisor that had 9 mm crown and 14 mm root lengths was simulated. The centre of rotation was accepted at the middle third level of the root. Simulation was performed according to the 1°, 5°, and 10° protrusion sequences between 90° and 180°. The amounts of relative intrusion to the true horizontal line were calculated by using a trigonometric formula. The initial axial inclination was an important factor on bite opening. Increased initial axial inclinations cause much more relative intrusion compared with the lower initial values. The initial incisor axial inclination has an effect on the bite opening aspect of protrusion.