Correlation analysis between tongue posture and hyoid bone position and cephalometric analysis variables in adult female patients

Abstract

Introduction: Despite of many previous studies, the relationships of long face and open bite to tongue and hyoid bond position are uncertain. The purpose of this study are to examine whether patients with long face and open bite have lower tongue and hyoid bone position or not, and to examine which cephalometric variables are closely correlated with tongue and hyoid bone position.

Methods: Two hundred twenty-seven Korean adult female patients aged over 18 years were evaluated. Lateral cephalograms of each subject were traced and several landmarks were digitized, then analysis was performed. Distance from the dorsum of tongue to palatal plane and distance from hyoidale to mandibular plane were used to represent tongue and hyoid bone position, respectively. The samples were divided into three groups for all three categories. First category is divided by the amount of overbite (open bite group, moderate overbite group and deep overbite group). Second category is divided by skeletal vertical pattern (high angle group, normal angle group and low angle group). Third category is divided by sagittal skeletal classification (Class I, Class II and Class III). ANOVA test was used to distinguish the differeneces among groups. Pearson's correlation test was used to detect correlation of cephalometric variables with tongue and hyoid bone position.

Results: In the comparison of overbite groups, there were no significant differences in tongue and hyoid bond position. However in the comparison of skeletal vertical pattern groups, tongue position of high angle group was lower than that of low angle group, and hyoid bond position of high angle group was lower than those of the other two groups. In the comparison of sagittal skeletal classification groups, there was no difference in tongue position, but hyoid bone position of Class II group was lower than that of the other two groups. Correlation analysis showed that variables of anterior facial height, upper Incisor display, facial length are most closely correlated with tongue position and the variables of ramus height, posterior facial height, frankfort mandibular plane angle are most correlated with hyoid bone position.

Conclusions: This study suggests that long face with long anterior facial height tends to have lowerly positioned tongue, and long face with short posterior facial height tends to have lowerly positioned hyoid bone. Open bite only is not seemed to be correlated with tongue and hyoid position. Tongue and hyoid bone position are more related with vertical skeletal pattern than dental overbite pattern.