Summary: The effect of lip training was studied in 15 children with incompetent lips, who were compared with a control group of 10 children who also had incompetent lips. Lip function was evaluated by electromyography of the activity of the lips in resting posture and during swallowing and chewing. The morphology of the dentition, facial skeleton and lips were studied on dental casts and profile radiographs. Lip training was performed for one year and was found to maintain lip function in the test group, in contrast to impairment of lip function in the control group. Lip training favorably influenced lip morphology, increasing the height of both lips and decreasing the interlabial gap. In the control group, the interlabial gap increased. The beneficial effect of the training on the function and morphology of the lips could not be shown to affect tooth position during the one-year study period.
Ingervall, B., & Eliasson, G. (1984). Effect of lip training in children with short upper lip, International Journal of Orofacial Myology, 10 (3), 17-26.