|Budget Amount *help
¥2,100,000 (Direct Cost : ¥2,100,000)
Fiscal Year 1995 : ¥600,000 (Direct Cost : ¥600,000)
Fiscal Year 1994 : ¥400,000 (Direct Cost : ¥400,000)
Fiscal Year 1993 : ¥1,100,000 (Direct Cost : ¥1,100,000)
To investigate the relation between the function of lips and morphology of both jaws, we have developed a simple device that allows measurement of lip pressure.
A metal plate is inserted under the lip, and pulled outward. The subject is asked to apply force to prevent the release of the plate. The resistance force is considered as the maximum lip strength and is measured for both lips separately. The plate is connected to a force gauge, and the signal is input into a portable computer.
The ordinary strength can usually be calculated from the maximum muscle strength (ordinary strength 20-30% of the maximum strength), besides there is a close relation between morphology and strength (maximum strength is proportional to the cross-sectional area). As lips are not thougth to be isolated or completely independent organs, they are believed to influence at least on the anterior part of the maxillo-facial complex. Based on this idea, we conducted a study on 24 subjects to cxamine the relation between the maximum strength of both lips, and the maxillo-facial complex. The hard tissue was evaluated on cephalograms, and the soft tissue were evaluated on photographs.
The lower lip showed stronger correlation to the morphology of the maxillo-facial complex more than the upper lip did. In skeletal patterns, the coefficient correlation between the lower lip and ANB was r=-0.427, for A-B plane it was r=0.460. In dental patterns the coefficient correlation for U-1 to SN r=0.398, for L-1 to SN it was r=0.313. As to the soft tissue, the coefficient correlation between the lower lip and the lower face was r=0.463. The coefficient correlation between the maximum strength of both lips was r=0.418.
It is therefore concluded that, the mandible has a tendency to develop in all direction in people with high maximum strength of the lower lip.