Standard and Limit Values of Mandibular Condylar and Incisal Movement Capacity

A clinical functional status was obtained and an instrumental analysis of functional movement patterns of the mandible using the ultrasonic Jaw Motion Analyzer (JMA, Zebris; Isny, Germany) was performed on 259 subjects (100 male, 159 female) who were part of an associated project of the representative population-based Study of Health in Pomerania (SHIP 0). Standardized bilateral "arbitrary" skin points based on anatomical skin references were assumed as posterior reference points in the joint area. The recorded movement patterns were evaluated for condylar movement capacity right and left upon mouth opening (COR and COL, in mm), the incisal right-lateral and left-lateral excursion capacity (IR and IL, in mm), the incisal opening capacity (IO, in mm), and the maximum opening angle (OA, in degrees). For the determination of the standard and limit, the following means were determined with standard deviations and 5th and 95th percentiles: COR 14.52 ± 4.188 (7.70, 21.40); COL 15.07 ± 4.788 (7.60, 21.80); IR 8.92 ± 2.403 (5.20, 13.00); IL -8,79 ± 2.455 (4.80, 13.00); IO 44.34 ± 7.388 (33.40; 56.10); OA 32.16 ± 5.954 (21.40; 41.80). The values for men vs women for IR and for OW and in the age group below 40 years vs 40 years and above for IR were statistically significantly different. Interestingly, the interval between the 5th and 95th percentile in the group with a Helkimo clinical dysfunction index of 1 and approximately the same mean value was significantly greater than in the group with Helkimo 0. Based on this standard and limit values or ranges, individually measured values of functional mandibular movement can be compared and differentiated with respect to hypomobility/limitation ( 5th percentile) or hypermobility (> 95th percentile). This serves to indicate the therapeutic direction for functional treatment to improve the jaw's movement capacity in terms of biomechanical optimization. Objective kinematic measurements can be used for additional documentation of the treatment progress during the treatment course. Keywords: population-based values of mandibular function, condylar movement, incisal movement, instrumental devices, electronic axiography, jaw tracking