Relationship between lip strength and lip function in posture and chewing

Abstract

The relationship between lip strength, measured clinically with a dynamometer, and the electromyographically recorded activity of the lips at rest and during chewing was studied in 50 children, aged 7 to 13 years, with varying types of malocclusion. The electromyographic activity of the lips was also related to bite and facial morphology recorded on dental casts and profile radiographs. There was no correlation between lip strength and the EMG activity of the lips at rest or during chewing. The postural lip activity was not correlated to dentoalveolar cephalometric variables, including incisor relationship and inclination, but was correlated to lower arch width and the thickness of the upper lip. The activity of the lips during chewing was correlated to dental arch size, to incisor relationship and to lip morphology and relationship. This was interpreted as an adaptation of the chewing activity to bite morphology. There was no evidence that lip function influenced bite morphology.