Methods: Ten subjects (4 men - 6 women, ages 25 - 47) at UTHSCSA were selected to evaluate this relationship. A Denar(D) kinematic facebow was attached to the mandibular teeth with Aquaseal( polyvinylsiloxane impression material) and the hinge axis pins were placed at an initial arbitrary hinge axis location described by the manufacturer(D). This location was established on a line thirteen mm anterior to the top of the tragus and the most anterior part of the external auditory meatus on a line with the anterior point being 43 mm superior to the distal incisal line angle of the maxillary right central incisor. In the centric relation position the patient was instructed to open less than one half inch. The (D) facebow was adjusted by viewing an initial arc of the hinge axis pins at the arbitrary hinge axis location; then adjusting the facebow until there was an exact rotation of the pins without any arc. The facebow was removed for approximately one half hour; and then placed back on the patient’s face; and the hinge axis location reestablished.
Results: There was no statistical difference p < 0.05 using a paired t-test between the two hinge axis locations. The means for the right and left hinge axis locations were 0.89 mm and 0.87 mm and the range of the right hinge axis was 0.00 to 2.42 and the left hinge axis 0.00 to 1.06.
Conclusions: Although the two hinge axis locations established for each subject on the right and left sides were close, there were only two subjects that the investigators established the same hinge axis position at the two different time points. The true hinge axis location could only be repeated 20% of the time.