The value of clinical lip strength measurements.

The strength of the lips was measured with a dynamometer in fifty children, aged 7 to 13 years, with varying types of malocclusion. The lip strength was related to the electromyographically recorded activity of the lips during the lip strength measurements and to bite and facial morphology. The morphology was recorded on dental casts and profile radiographs. The lip strength measurements were found, in duplicate determinations, to have limited reproducibility. There was no correlation between lip strength and the EMG activity of the lips during the recordings. Lip strength was not correlated to dentoalveolar cephalometric variables, including relationship and inclination of the incisors. Nor was there any correlation between lip strength and lip morphology. The value of lip strength measurements seems to be limited, due either to difficulties in recording lip strength or to a small influence of lip muscle forces on the dentition.