Purpose: The objectives of this study were to determine how changes in body and head position undergoing dental treatment affect mandibular position, and to develop a set of standards for patient posture.
Methods: Mandibular position was investigated in 8 subjects with normal occlusion and not suffering any stomatognathic dysfunction. This was done by measuring the location of the tapping point on the incisal point using a Gnathohexagraph (a 3-dimensional jaw movement measurement device with 6 degrees of freedom), with the subject’s head in 4 different positions while sitting, and the body and head in 16 different positions with the subject supine, and then comparing deviation from the reference position in each of these positions. Statistical analysis of data was performed using first, repeated measures of 1-way ANOVA (α=.05), second Bonferroni’s multiple comparison test was undertaken in seated positions. In supine positions, repeated measures of 2-way ANOVA was performed, and followed by Bonferroni’s multiple comparison test was performed.
Results: The incisal point deviated significantly in the anteroposterior direction due to changes in head and body position. With the subjects seated, the incisal point tended to move backwards when the subjects were asked to lean backwards from the reference position. The incisal point tended to move forward when the subjects were asked to lean forward. With the subjects in a supine position, the incisal point was inclined backwards. The degree of backwards inclination of the incisal point tended to decline as the head position was varied from 10 degrees backwards to 20 degrees forward, regardless of the degree of backwards inclination of the body.
Conclusion: Changes in body and head posture undergoing dental treatment affect incisal point deviation.