Background: The objective of this study was to evaluate the relationship between hyoid bone position and severity of obstructive sleep apnea (OSA), and to investigate its value as a complementary diagnostic method. Methods: A total of 133 patients who were diagnosed as OSA with an apnea-hypopnea index ≥ 5 were included. Clinical examination, level I polysomnography (PSG) and lateral cephalographic analysis were done. Comprehensive PSG characteristics were compared according to hyoid bone position and the predictive power of the distance between the mandible and hyoid was assessed. Results: The distance between the hyoid bone and mandibular plane was significantly longer in the severe OSA group (p = 0.013). The distance from hyoid bone to third vertebrae (C3) and hyoid bone to mentum were also longer in the severe OSA group but the difference did not reach statistical significance. The distance between hyoid bone and mandibular plane was effective in predicting severe OSA, with a cut-off value of 19.45 mm (AUC = 0.623, p = 0.040). When grouped according to a distance cut-off value of 19.45 mm, those with a longer distance between the hyoid bone and mandibular plane showed more respiratory disturbance, lower oxygen saturation levels, less deep slow wave sleep, and more fragmented sleep with arousals. Conclusions: The distance between the hyoid bone and mandibular plane derived from cephalometric analysis can be a valuable diagnostic parameter that can be easily applied in differentiating severe OSA patients.

The aims of this study were to investigate the gender differences in signs and symptoms of Korean Temporomandibular Disorder (TMD) patients based on Research Diagnostic Criteria for Temporomandibular Disorders (RDC/TMD) and psychosocial characteristics. A total of 1052 patients with TMD were evaluated with a questionnaire for medical history, clinical symptoms, and contributing factors, clinical examination based on RDC/TMD, and radiographic examination. RDC/TMD axis II and Symptom Checklist-90-Revision (SCL-90-R) were administered to evaluate pain-related disability level and psychological status of patients. The prevalence of TMD was higher in women than men, and the women were older than the men. The women showed higher prevalence of myogenous pain, mixed pain, disc displacement without reduction, osteoarthritis, headache, subjective insomnia, pain intensity, number of positive muscle palpation, and the high disability group in the grade chronic pain scale. Gender was associated with the number of positive muscle palpation and maximum mouth opening. Pain intensity was not associated with gender, but with number of systemic comorbidities. Subjective symptoms, and clinical and psychological characteristics of patients with TMD showed gender differences. To achieve understanding of patient and increase of success rate of treatment of TMD, gender should be considered in patient evaluations and treatment approaches.