Comparison of the functional occlusal plane in adults with class III malocclusion showing open bite and non-open bite.

A retrospective study of lateral cephalograms of 24 Japanese adults with Class III malocclusion was made in order to compare the angles of the horizontal plane between open bite and non-open bite cases. The following results were obtained: i) There was no significant difference in the angle of the NF-upper occlusal plane between the open bite and non-open bite groups. ii) There were significant differences between the two groups in the angle of the SN-upper and lower occlusal planes, the FH-upper and lower occlusal planes and MP-lower occlusal plane. There was also a significant difference between the groups in the distance from the Xi point to the upper occlusal plane. iii) In both the open bite and non-open bite groups there was a wide variation in occlusal plane angles, compared with normal cases.