A Study on an Face-bow with a Sliding lintercondylar Axis Mechanism

Part 1-Position of an Arbitrary Hinge Axis Obtained by an Ear-bow

Abstract

Position of an arbitrary hinge axis obtained by means of an ear-bow with a sliding intercondylar axis mechanism was compared with that of true hinge axis.
Ten patients without any clinically significant symptoms of occlusion were selected as the subjects. Face-bow transfers employing arbitrary hinge axis and true hinge axis were performed, and maxillary stone casts were mounted on an articulator, respectively. Position of the maxillary stone cast oriented with arbitrary hinge axis was determined in comparison with that oriented with true hinge axis, and dimensional discrepancy between those was evaluated.
Results are as follows:
1) Arbitrary hinge axis obtained by means of an ear-bow had average dimensional discrepancy of 6.05 mm to terminal hinge axis. 60 percents of the subjects have discrepancy less than 5 mm.
2) Arbitrary hinge axis reproduced on an articulator tends to be located backward and downward. This is considered due to illf itting of the ear-piece to the auditory meatus.
3) There was no indication that the reference pin index depressed the accuracy of reproducibility of opening and closing axis.