Temporomandibular disorder and generalized joint hypermobility: electromyographic analysis of the masticatory muscles

is study aimed to verify the presence of generalized joint hypermobility (GHJ) in individuals with temporomandibular disorders (TMD) and asymptomatic individuals and to compare the activity of their masticatory muscles. Methods: 61 female patients aged 18 to 35 years were evaluated: 34 with diagnosis of TMD by the Research Diagnostic Criteria for Temporomandibular Disorders constituted the TMD group and 27 constituted the asymptomatic group. The subgroups were classified according to the presence of GJH by the Beighton score. Electromyographic recordings of the masseter and anterior temporal muscles were acquired bilaterally at mandibular rest and in maximal intercuspal position. Results: GJH was present in 64.71% of the individuals with TMD and in 40.74% of the asymptomatic individuals. The electrical activity was significantly higher in the right masseter (p = 0.0111), left masseter (p = 0.0007) and right temporal (p = 0.0046) in the patients with TMD than in the asymptomatic individuals. The activity of the left masseter muscle was significantly higher (p=0.0072) in the volunteers with TMD and GJH compared with in the individuals with TMD but without hypermobility. Also, the right temporal muscle showed higher activity in subjects with GJH and TMD compared with asymptomatic individuals without hypermobility (p=0.0248). Conclusions: The electrical activity was higher at mandibular rest in TMD and TMD/GJH patients. This result suggests that these muscles need to be recruited for the joint stabilization due to the low ligamentar resistance and a possible proprioceptive deficit. This recruitment appears to occur asymmetric and variedly among all muscles involved in this stabilization, which could compensate for the low ligamentar competence and a possible proprioceptive deficit in individuals with GJH. Both TMD and GJH seem to have influenced the muscular activity