Lip seal study of Japanese adults with malocclusion.

The purpose of this study to clarify the factors an effecting lip seal in Japanese adults with malocclusion. Sixty-three malocclusion patients aged 20 to 27 years were randomly selected and compared with fourteen normal occlusion controls aged 22 to 26 years old. The subjects were divided into a good seal group and a poor lip seal group by observing the distance between the upper and lower lip at rest. Results of this adult study were as follows; There were no poor lip seals in normal occlusion subjects. Significant differences were observed for tongue thrust (p < 0.05) and mouth breathing (p < 0.05) between the good lip seal group and poor lip seal group of malocclusion subjects. Adults with poor lip seal should be treated for their malocclusion prior to be other functional approaches to improving their lip seal.