Features related to EMG-activity of masticatory muscles in patients with unilateral posterior crossbite: a cross-sectional study

Introduction
The worldwide prevalence of posterior crossbite was in a range from 5% to 14 %. The etiology of posterior crossbite can include combination of dental, skeletal, and neuromuscular functional components. EMG has been used to identify different muscle patterns and compare diagnostic data in individuals.

Aim
The aim of the study was to investigate features of EMG-activity of masticatory muscles in adults with unilateral posterior crossbite.

Material and methods
The study evaluated EMG-activity of masticatory muscles of 26 subjects of 20-28 years aged with unilateral posterior crossbite. The average age was 23.4 ± 2.1 years. 12 (46.2%) were men, 14 (53.8%) were women. The control group for comparison consisted of 30 sex-matched individuals without malocclusion

Results
In one-side teeth clenching tests EMG-activity of anterior temporal and masseter muscle was higher on crossbite side, whether it was working or balancing side. In the right-side teeth clenching test anterior temporalis muscle was more active on the balancing side in the study group comparing with the control group. In the left-side teeth clenching test masseter muscle on the balancing side (right) was more active in the subjects of the study group. In the maximum voluntary clenching test higher EMG-activity of the anterior temporal and masseter muscle was found on the crossbite side.

Conclusions
Patients with crossbite are characterized by asymmetric EMG-activity of muscles on the right and left sides due to increased EMG-activity of the masticatory muscles on the crossbite side.