Abstract
The use of oral appliances for the treatment of obstructive sleep apnoea (OSA) has become an established treatment choice. To date, follow-up data on the effects of such treatment on the facial skeleton, pharynx and occlusion have been limited.
A study has subsequently been designed to address these issues. One hundred consecutively treated medically referred patients (87 males, 13 females, mean age 49 years, SD 8.5), were reviewed cephalometrically in six month intervals (6-30 months) following treatment with mandibular advancement therapy. Reference points and planes were digitized with a reflex metrograph and their means converted to linear and angular measurements. The mean mandibular advancement was 6.8mm (SD 1.8). No relationship was found between occlusal changes, degree of mandibular advancement, skeletal classification, duration of treatment, age or sex (ANOVA). When all patients were compared (N 100) occlusal changes related to a reduction in overbite (-l.02mm p<0.0001) and overjet (1.06mm p<0.0001) this was associated with a retroclination of the upper anteriors (-1.9° p<0.0001) and a proclination of the lower anteriors (2.8° p<0.001). A reduction in maxillary arch length was also found (-0.47mm p<0.006). Skeletal differences included small statistically significant changes in SNA0 (p<0.023), ANB0 (p<0.013) and maxillary length (p<0.002). A change in the vertical position of the mandibular condyle was highly significant (p<0.0001). When the changes over time were determined, an increase in face height and reduction in overbite and overjet were evident at 6 months associated with a change in condylar position. Over-eruption of the maxillary first premolars and mandibular first molars, along with a proclination of the lower incisors were only evident at 24 months. Occlusal changes tended to be progressive with on-going treatment with the greatest changes occurring at the final review period (30 months). Significant positive correlations were found also between the amount of anterior opening by the appliances and changes in overbite at 24 and 30 months.
Although changes were not evident in either hypopharyngeal width or hyoid bone position, long-term mandibular advancement does, however, have a demonstratable effect on both the oropharynx and velopharynx. Following 12 months of treatment, posterior airway space (PAS) increased from 10.7 to 12.0mm (p<0.009). Statistically significant changes in the velopharynx were observed as early as six months with a reduction in length of the soft palate of 1.5mm (p<0.0001 ). These changes were considered to be due to the loss of pharyngeal odema following the elimination of habitual snoring. A change in natural head position (NHP) from an extended to a more upright position was also significant .
Cephalometric differentiation between patients with mild or moderate OSA and those diagnosed with non-apneic snoring have been limited. Of this sample (NlOO), 58 patients were referred for the treatment of mild to moderate OSA and 42 for the treatment of nonapnoeic snoring. No statistically significant differences were observed between the apnoeic and non-apnoeic patients in either their skeletal or cranial base dimensions. Nasopharyngeal depth was, however, reduced in the apnoeic group.