Standard and limit values for the symmetry of articulation parameters in the temporomandibular joint area - evaluations of the associated project of the SHIP study

The articulation parameters, especially the horizontal condylar inclination angle (HCI), the Bennett angle (BA), and the immediate side shift (ISS) were determined in 259 subjects (100 males; 159 females) of the associated project with reference to the population-representative baseline study (Study of Health in Pomerania, SHIP 0). The evaluations were based on a clinical functional status and electronic motion recording with the ultrasonic measuring system Jaw Motion Analyser (JMA, Zebris, Isny, Germany). The reference plane, to which all measured values were represented and the HCI calculated, was the hinge axis infraorbital plane (HA-IOP). The HCI was determined after an excursive movement with a length of 4 mm to the HA-IOP in the sagittal view and the BA after a mediotrusive excursion movement of 6 mm in the horizontal view to the midsagittal plane. For the standard and limit values, the average value in addition to the standard deviation and the 10th and 90th percentile value (10th percentile value, 90th percentile value) were determined: HCI right 52.1 +/- 10.14 degrees (39.4 degrees, 64.0 degrees), HCI left 53.1 +/- 9.67 degrees (42.3 degrees, 67.0 degrees), BA right 15.2 +/- 7.53 degrees (6.7 degrees, 25.0 degrees), BA left 14.2 +/- 7.84 degrees (5.4 degrees, 24.1 degrees). The HCI was approximately 2 to 3 degrees larger in females (males: right 50.5 +/- 9.47 degrees, left 51.9 +/- 8.99 degrees; females: right 53.1 +/- 10.42 degrees, left 53.8 +/- 10.03 degrees). Likewise, the BA in the age group >= 40 years (males: right 14.4 +/- 6.62 degrees, left 13.1 +/- 7.14 degrees; females: right 17.0 +/- 9.02 degrees, left 16.9 +/- 8.72 degrees). The latter proved to be statistically significant in the t test for independent samples, assuming variance equivalence on the right, with P =0.009, and with rejection of the variant equivalence on the left, with P = 0.002. The right and left HCI and BA joint values showed highly significant linear dependence at P < 0.001, b