2017 Volume 55 Issue 1 Pages 1-10
We investigated the development of lip closing force and other forces, and their relationships to elucidate their effects on dentition formation, as well as dental occlusion and swallowing. Method : A total of 45 subjects with normal occlusion ranging in age from 8-25 years old were investigated. Lip closing force was determined using a multidirectional lip closing force measurement system. Tongue and buccal pressure measurements were obtained with a simple tongue pressure measurement device, and grip strength with a Smedley hand dynamometer. Results : Subjects in the 8-year-old age group had significantly greater lip closure force from the lower jaw in all 8 directions of lip closing force as compared to subjects older than 11 years. As for the correlation of lip closure force with other forces, tongue pressure on the palate had a greater positive correlation with lip closure force in older subjects in an age-dependent manner. In addition, a positive correlation of buccal force with dentition and grip strength was observed in all age groups. Discussion : Our findings revealed that lip closing function in younger ages occurs mainly in conjunction with lip closing force from the lower jaw, while the lip as a whole moves in a more coordinated manner with maturity. Furthermore, they suggest a correlation of lip closing force with tongue and buccal pressure, each of which work in coordination for oral function.
