Positional changes of hyoid bone and cranio-cervical posture following class III orthopedic treatment.

AIM: The purpose of this study was to evaluate hyoid changes after skeletal class III therapy and, particularly, after chin-cup and Delaire face mask treatment.

METHODS

This analysis was carried out by taking pretreatment (T1) and posttreatment (T2) lateral cephalometric radiographs of 30 patients (18 males and 12 females) with craniofacial skeletal class III cephalometrics traits; their age, at the time of starting treatment, ranged from 9 years to 13 years and 2 months, with an average of 11.02+/-1.23.

RESULTS

In the 2 samples there were highly significant differences for H-H1 (P<0.01), C3-H and hyoid angle, which mean an inferior hyoid bone position with a decrease of distance between mandibula, vertebral column and hyoid bone. Postural items showed a highly significant posterior inclination of the cervical vertebral column; in chin-cup subjects there was a hypoextension of the head.

CONCLUSIONS

The inferior position of the hyoid bone, in both the samples examined, and the hypoextension of the head, could point out the function of hyoid bone as an ''organ of respiration'' , since the variation of its position, as a sign of a new muscular equilibrium, should help to maintain the patency of the upper airways.