Abstract
The objective of this study was to clarify the characteristics of lip-closing force (LCF) measured by the novel developed multidirectional LCF measurement system and evaluate the relationship between LCF and physiques or physical strengths in the early stage of permanent anterior teeth occlusion. In 242 primary school children (136 boys, 106 girls, mean age = 10.3 ± 0.3 years), LCFs in eight directions during maximum voluntary pursing-like lip closure tasks, height, body weight, handgrip strength and bite force were recorded in two primary schools in Nagano as field research. The gender difference of summed values of LCFs for all eight directions (total lip-closing force [TLCF]), the correlation between TLCF and each directional LCF (DLCF), between opposing DLCFs and between TLCF and height, body weight, handgrip strength and bite force were statistically analyzed. TLCF in boys was significantly greater than that in girls. The DLCFs was large by vertical, oblique and horizontal directions order. There were significant correlations between TLCF and DLCFs except horizontal directions and between most pairs of opposing DLCFs. Symmetrical outputs in most pairs of opposing DLCFs were also observed. In girls, there were significant correlations between TLCF and height, body weight, handgrip strength or bite force, however in boys, there were significant only between TLCF and body weight or handgrip strength. In the early stage of permanent anterior teeth occlusion, LCF showed unique directional specificity in vertical, horizontal, oblique and opposing directions. And the present results suggested that LCF was related to the ability for volitional movement.
