Background The muscle impairment in Temporomandibular disorders (TMDs)1, frequently observed in patients with different rheumatic diseases, contribute to diminished recruitment and force tuning ability. The quantitative assessment of the motor function is capital in the diagnosis and rehabilitation of TMDs. In this study, we propose an intuitive visual feedback of the bite force that promote the coordination and control of jaw muscles.
Objectives Validity and reliability evaluation of a visual feedback system for masticatory muscle assessment
Methods The force signals, measured by two customized force transducers positioned between the first molars teeth, became the spatial coordinates of a cursor which moved on a PC monitor according to the subject's bite force on the right (axis x) and left sensors (axis y). The subject's force during a maximal monolateral left (Lx, Ly), monolateral right (Rx, Ry) and bilateral (BILx, BILy) clenching outlined the boundaries of the Working Area (WA) (Figure 1). During a trial, the task required was to match the position of the 23 targets randomly displayed within the WA, each target being displayed for 5 s and alternated with 5 s of rest. Each subject performed two sessions of three trials in two consecutive days. Matching errors were measured by Mean Distance (MD), calculated as the mean cursor-target distance, and Offset Error (OE), calculated as the distance between the mean cursor position and the target. For the reliability analysis of MD and OE, we considered the Intraclass Correlation Coefficient (ICC), the Standard Error of Measurement (SEM), and the Limits of Agreement (LOA). The validity of both indices was investigated with a linear regression analysis. A 2-way repeated measures ANOVA with SESSION (2 levels) and TRIAL (3 levels) as factors was done to control for any learning effect.
Results The 13 subjects included showed a wide range of WAs, geometrically representing functional aspects like maximal force, and left/right independence in force generation. MD showed a more acceptable reliability (ICC =0.78, 95%CI 0.43-0.93;SEM =26%;LOA = -29%, 23%) instead of OE (ICC=0.66, 95%CI 0.20–0.88; SEM=37%; LOA = -31%, 42%). The correlation between MD and OE was high (r=0.96, p<0.001). The 2-way ANOVA detected a significant decrease for MD (p=0.004) and OE (p=0.012) between the two sessions.
Conclusions This visual feedback system provided a valid and reliable representation of the mandibular motor function to be extended in the evaluation of patients suffering from rheumatic diseases. The use of error indices (MD, OE) may characterize the individual performance during force control tasks of jaw elevator muscles in health and disease. This technique may also provide specific rehabilitation programs for TMDs because the subject's improvement during the second session was most likely attributable to a learning effect.
Manfredini D, Guarda-Nardini L, Winocur E, et al., Research diagnostic criteria for temporomandibular disorders: a systematic review of axis I epidemiologic findings. Oral Surg Oral Med Oral Pathol Oral Radiol Endod 2011;112:453.
Disclosure of Interest : None declared