Effect of Different Treatment Modalities on Masseter Inhibitory Reflex in Patients with Sleep Bruxism: A Case-Control Study

Sleep bruxism (SB) is a parafunctional oral habit that is frequently related to sleep arousals. The masseter inhibitory reflex (MIR) causes reflex inhibition of voluntary contractions of the elevator muscles induced by intense peri- or intraoral mechanical or electrical stimulations. This study aimed to investigate the changes in MIR of patients with SB, and the effect of different treatment modalities on MIR.

In this case-control study, 100 individuals were randomly assigned to four groups (n=25) of conservative treatment (G1), occlusal splint treatment (G2), low-level laser therapy (LLLT) treatment (G3); and control (G4). The MIR was tested in all participants before and one month after treatment. 

All MIR components of the patients had longer right and left SP1 and right and left SP2 latencies (P=0.017, P=0.043, P<0.001, and P=0.04, respectively), and shorter right and left SP1 and right and left SP2 durations (P=0.021, P=0.021, P<0.001, and P<0.001, respectively) as compared to the control group. The right SP1 and SP2 latencies were prolonged in G3 versus G1 and G2 (P=0.026 and P<0.001, respectively); whereas, the left SP2 latency was prolonged in G2 compared with G1. The right and left SP2 duration was not significantly different among the three treated groups. The left SP1 duration was not significantly different among the three treated groups. Gender had no effect on MIR parameters.

SB patients had an abnormal MIR response. LLLT was the most effective compared to other treatment modalities.