Bite force and electromyographic activity of the masseter muscle in children with hemifacial microsomia.

Hemifacial microsomia (HFM) is a malformation characterized by asymmetric facial growth with mandibular and muscular involvement. There are no reports focused on the functional status of the masticatory system of patients with HFM. The objective of this work evaluate bite force and electrical activity of masseter muscle in children with HFM, and compare them to healthy controls. A cross-sectional study was performed to compare bite force and electrical activity of masseter muscle between subjects with HFM and healthy children. Mean bite force (MBF) and surface electromyography (EMG) on maximum intercuspation (MIC) and rest position (RP) from both sides of the face were recorded. Comparative statistics between HFM patients and controls were performed using the Mann-Whitney test, Wilcoxon's signed rank test was used to compare the microsomic and healthy hemifaces. Twenty children with HFM and 10 controls were included, average age was 7.2 years (range 3-14). MBF did not show statistical significance between both groups. Surface EMG signal at MIC was significantly diminished when compared to the healthy side ( p  = .003) and to the control group ( p  = .016), this significance was also present at RP when comparing the affected and non-affected sides of the face ( p  < .01) but not against the controls ( p  = .08). This study showed that patients with HFM had diminished EMG values of the masseter muscle on the affected side, compared to healthy individuals, but bite force did not show significant alterations.