Hyoid bone position and head posture comparison in skeletal Class I and Class II subjects: A retrospective cephalometric study

Objective: The aim of the study was to investigate the hyoid bone position and the head posture using lateral cephalograms in subjects with skeletal Class I and skeletal Class II pattern and to investigate the gender differences. Materials and Methods: The study used lateral cephalograms of 40 subjects (20 skeletal Class I pattern; 20 skeletal Class II pattern). Lateral cephalograms were traced and analyzed for evaluation of the hyoid bone position and the head posture using 34 parameters. Independent sample t-test was performed to compare the differences between the two groups and between genders in each group. Statistical tests were performed using NCSS 2007 software (NCSST, Kaysville, Utah, USA). Results: The linear measurements between the hyoid bone (H) and cervical spine (CV2ia), the nasion-sella line, palatal line nasion line, the anterior nasal spine (ANS) to perpendicular projection of H on the NLP (NLP- Nasal Linear Projection) (H-NLP/ANS) as well as the posterior cranial points (Bo, Ar and S points) were found to be less in skeletal Class II subjects. The measurement H-CV2ia was found to be less in males with skeletal Class I pattern and H-CV4ia was found to be less in males with skeletal Class II pattern. The natural head posture showed no significant gender differences. Conclusion: The position of hyoid bone was closer to the cervical vertebra horizontally in skeletal Class II subjects when compared with skeletal Class I subjects. In males, the hyoid bone position was closer to the cervical vertebra horizontally both in skeletal Class I and skeletal Class II subjects