The dependence on posture of temporalis and masseter bioelectrical muscle activity

Background: Masticatory dysfunctions are a common problem in society today. Disorders such as clenching, bruxism can lead to a loosening of teeth in the jaw, abrasion of the tooth crowns, inflammatory changes, and ultimately degenerative changes in the temporo-mandibular joints.Aim: The aim of this study was to assess the relationship between masseter and temporalis anterior muscles activity and body posture.Material and Methods: In 20 subjects (20-35 years) the sEMG of the masseter and temporalis anterior muscles was measured twice during functional clenching: in casual posture and in posture with the head in retraction. The study was conducted using sEMG Tele-Myo (Noraxon). Results: The bioelectrical activity of the evaluated muscles was significantly higher in the casual posture than in retraction (p<0.05). Temporomandibular disorders appear not only due to facial muscle activity abnormalities, but also due to incorrect body posture, especially a head forward posture. The measurement was performed twice in a sitting position: in casual posture and in a posture with the head in retraction. Mean masseter activity during teeth clenching was statistically significant in retraction compared to the habitual position (p<0.05), both for the left and right side. There was also statistically significant activity in the temporalis muscles in retraction compared to the habitual position.Conclusion: The observed decreased activities in both the masseters and temporalis muscles suggest that masticatory system dysfunctions may not only be the result of dysfunction in the craniofacial region but also may be posture dependent.