Abstract
Purpose: The objectives of this study were to determine how a change in head position while a patient undergoes dental treatment affects the condylar position, and to develop a set of standards for the patient's posture.
Methods: The condylar position was investigated in 8 subjects with normal occlusion and suffering no stomatognathic dysfunction. This was done by measuring deviation in the anteroposterior and vertical directions, and all 8 subjects attached an anterior jig. The measurement condition consisted of 4 kinds of headpositions (0 degrees, backward 10 degrees, forward 10 degrees, or forward 20 degrees from the referenceposition) while sitting and tapping on the incisal point. The measuring equipment was theexercise Gnathohexagraph®, which measures a 3-dimensional jaw with 6 degrees of freedom. The Frankfurt plane was adopted as the reference plane for Gnathohexagraph® measurement, and Beyron's point was used as the measurement point. The anteroposterior direction and the vertical direction were determined.
Results: Forward tilting of the head tended to cause a forward inclination of the condylar point, and backward tilting tended to cause backward condylar point inclination. The degree of backward mandibular inclination tended to decrease as the head was successively moved from 10 degrees backward to 0 degrees, from 10 degrees backward to 20 degrees forward.
Conclusion: It was suggested that the condylar point deviated significantly in the anteroposterior direction and the vertical direction because of changes in head positions. Consequently, it was necessary to consider the head position of the patient at the occlusal registration recording or the occlusal contact adjustment.
