Accuracy of an earpiece face-bow

The validity of the Hanau ear-bow to transfer an arbitrary hinge axis to a Hanau articulator was clinically compared with a Hanau kinematic face-bow. The study was conducted with 18 randomly selected patients. This investigation demonstrated a significant statistical difference between the arbitrary axis located with an ear-bow and the terminal hinge axis. This discrepancy was significant in the anteroposterior direction but not in the superior-inferior direction. Only 50% of the arbitrary hinge axes were within a 5 mm radius of the terminal hinge axis, while 89% were within a 6 mm radius. Furthermore, the ear-bow method was not repeatable statistically. Additional study is needed to determine the practical value of the arbitrary face-bow and to pursue modifications to improve its accuracy.