Differences between sexes in maximum jaw opening when corrected to body size.

According to linear interincisal measurements, women have a smaller maximum jaw opening than men. In this study the difference was 2.7%. In contrast, epidemiological surveys indicate that women have a greater mobility of joints and generally more joint laxity. Covariate analysis was used to test for the difference between sexes in mean maximum passive opening adjusted according to group mean differences in other parameters of body size. The net result was that the values became more equal between sexes. A second method, employing a geometric estimation for the angle of maximum jaw opening, showed that women had a 5.4% wider range of jaw opening than men (P less than 0.057). This method avoided the problem of considering relative body size and body factors which generally correlated poorly with maximum opening. It should be noted that an increased range of opening is a measure of hyperextensibility and does not necessarily imply laxity or instability.