Change of Incisor Inclination Effects on Points A and B

Objective: To identify and evaluate changes in the cephalometric position of points A and B due to an incisal inclination change caused by orthodontic treatment. Materials and Method: A total of 103 pairs of consecutive pretreatment and posttreatment lateral cephalographs that met the inclusion criteria were systematically collected from the departmental database and digitized using a customized software program (Gela). Repeatability analyses showed good reliability and no evidence of bias. A statistical model was generated using a Generalized Estimating Equation approach to analyze the data accounting for growth and bodily movement because both factors influence the position of points A and B (P <.001, P <.001). Changes in tooth length were also accounted for, as these changes may influence the calculated position of the centroid (P =.002). Results: Each 100 change in the maxillary incisor inclination results in a statistically significant average change in point A of 0.4 mm in the horizontal plane (P =.028). Each 10 degrees change in the mandibular incisor inclination results in a borderline statistically significant average change in point B of 0.3 mm in the horizontal plane (P =.058). There were no significant changes in the vertical position of points A and B. Conclusion: The effects of incisal inclination changes, due to orthodontic treatment, are of no clinical relevance to the position of point A and B, even though they may be statistically significant. The validity of points A and B as skeletal landmarks generally holds true, and accounting for treatment changes is unnecessary. (Angle Orthod. 2009;79:462-467.)