CEPHALOMETRIC ASSESSMENT OF HYOID BONE POSITION IN NIGERIAN PATIENTS WITH BIMAXILLARY INCISOR PROCLINATION.

Background: Hyoid bone though constitute a small proportion of the human skeleton, its importance in relation to other facial structures cannot be overemphasized. Several studies have reported on hyoid bone position in relation to various types of malocclusion, however, to our knowledge, there has been no study on the relationship between the hyoid bone and bimaxillary incisor proclination.

Aim: The aim of this study was to assess the relative position of hyoid bone in individuals with and without bimaxillary incisor proclination as well as other related demographic factors.

Methodology: This was a comparative retrospective study of lateral cephalometric radiographs of orthodontic patients aged 12 to 40 years from two study locations (Ile-Ife and Lagos, Nigeria). Thirty randomly selected radiographs of patients with bimaxillary incisor proclination were compared with 30 radiographs of related cases with normal incisor relationship. These radiographs were manually traced using established cephalometric landmarks and analysed using SPSS 16. Independent t-test was used to compare mean values and statistical significant level was set as p<0.05.

Results: Most of the linear and angular dental/skeletal measurements in relation to hyoid bone position showed no significant differences within the compared groups. Hyoid bone position (H-TV) was found to be more anteriorly located in male (p=0.02) and in bimaxillary incisor proclination (p=0.004) patients than their female and normal incisor relationship groups respectively. Similarly, there was a highly statistically significant difference in linear measurement of the lower incisor tip to hyoid bone position (H-LIT) between the adolescent and young adult groups (p=0.01).

Conclusion: The hyoid bone position in male and bimaxillary incisor proclination subjects were more anteriorly located when compared with female and normal incisor relationship groups respectively. Similarly, the distance between the hyoid bone position and the lower incisor tip was longer in young adults than the adolescent group.