Effects of Parkinson's disease on molar bite force, electromyographic activity and muscle thickness of the masseter, temporal and sternocleidomastoid muscles: A case-control study

Background Parkinson's disease is a neurological disorder that promotes motor changes in the body. Objective The aim of this study was to investigate the impairment of the stomatognathic function regarding molar bite force, electromyographic activity and thickness of the craniocervical muscles in patients with Parkinson's disease in comparison with those in asymptomatic controls. Methods Twenty-four subjects were divided into two groups, a Parkinson's disease group (n = 12) and a control group (n = 12). The subjects were evaluated on the basis of molar bite force, electromyographic activity (rest, right and left laterality, protrusion, maximum voluntary contraction) and thickness (rest and maximum voluntary contraction) of the right and left temporal (anterior portion), masseter and sternocleidomastoid muscles. The results were submitted to a multivariate analysis of variance (MANOVA) to compare the means of the two independent groups, considering diagnosis of Parkinson's disease and craniocervical muscles as independent variables. For the post hoc comparisons, Bonferroni correction was used (P < 0.05). Results Parkinson's disease group presented lower mean values both sides for maximal molar bite force, significant increases in the electromyographic activities during mandibular tasks, lower mean thickness values of the masseter and sternocleidomastoid muscles, and higher mean thickness values of the temporalis muscles (anterior portion). Conclusion The results suggest that patients with Parkinson's disease may present functional changes of the stomatognathic system, related to bite force, electromyographic activity and thickness of the craniocervical muscles. The greater temporal muscle thickness in Parkinson's disease patients may compromise their daily life activities, especially with respect to chewing and nutrition.