Evaluation of the accuracy of three common methods in determining hinge axis points

Determining the true hinge axis point in order to transfer the orientation relation to articulator is of great importance in reducing occlusal errors. Because of the high cost and time consuming nature of kinematic method in determining hinge axis point, different arbitrary methods have been introduced which rendered controversial results throughout literature. The aim of this study was to evaluate some arbitrary methods for determining hinge axis point and to introduce a precise arbitrary method which has the least distance from kinematic point. This cross-sectional study was performed sequentially on 40 subjects without any TM- disorders with an age range of 21-37. At first true hinge axis point was determined by DENAR hinge axis locator and marked bilateraly on the skin. Then 3 arbitrary points (Beyron, Gysi, Tetruck & Laundeen) was also determined by a flexible ruler and marked on the skin. The distance between the arbitrary points and kinematic point was measured and the data were charted and subjected to Repeated ANOVA and Paired sample test. According to the results of the study, Beyron method was significantly more accurate than the other two methods. 88.88% of Beyron points were within 3 mm distance from kinematic point, but the other points didnt show any significant difference with each other. It is concluded that Beyron method has a high accuracy as an arbitrary method and because of its proximity to the true point, application of this method is recommended.