Maxillary Incisor Angulation and Its Effecton Molar Relationships

Abstract

To determine the variation in molar relationships when upper incisor angulations are altered in a Class I occlusion with normal overjet and overbite. Typodonts were set up to simulate a Class I occlusion on a normal skeletal base. The lower incisors were positioned normally at 92 degrees to the mandibular plane and the upper incisor angulations were altered from 90 degrees to 130 degrees by 2 degrees increments to the palatal plane. The changes in molar relationships were measured with every 2 degrees of upper incisor angulation change. A regression analysis was performed on the experimental data, and the regression coefficients, slope, and intercept were estimated. A negative linear relationship between upper incisor angulations and change in molar relationship was observed. On average, a change of 20 degrees in upper incisor angulation will alter the molar relationship by 1.8 mm. Changes in upper incisor angulations are significantly related to change in the molar relationship. Upper incisor angulations that deviate significantly from normal values are likely to result in less than ideal buccal segment relationships.