Predicting the effectiveness of an oral appliance for apnea treatment

Objectives: The efficacy rate of oral appliances for the treatment of obstructive sleep apnea hypopnea syndrome (OSAHS) is 50-80%. However, it is difficult to predict which patients will benefit from this treatment. The purpose of this study was to find the easy-measured variables which can predict the effectiveness of an oral appliance for the treatment of patients with OSAHS. Methods: Thirty-two patients (7 women and 25 men) diagnosed OSAHS by means of polysomnography participated in this study. Before treatment, overjet, overbite, maximum mandibular opening, and maximum protrusion were measured. All patients received a Herbst appliance with 70% of the maximum protrusion, and this advancement was progressively increased until the patient stopped snoring. Six weeks after the patient stopped snoring or the appliance did not work, a new polysomnography was carried out. Therapeutic efficacy was considered when a subjective improvement in symptoms was reported and a more than 50% reduction of apnea/hypopnea index (AHI) and an AHI value less than 10 was observed. Associations between treatment efficacy and factors were estimated by logistic regression analysis, and differences between groups were analysed using the student t test at p<0.05. Results: Four patients had to be excluded because lack of collaboration. Ten patients stopped using the device because different causes; occlusal changes, multiple fractures, discomfort or poor reduction of the AHI. The mean of overbite was 3.5 mm (SD 2.2) in patients with treatment success, and 1.3 mm (SD 1.6) in patients with treatment failure. Overbite showed a significant (p<0.05) corrected odds ratio of 2.5 (95%CI 1.1-6.5). However, the other variables were not significant predictors of treatment success. Conclusions: Despite the limitations of the present study, an overbite of more than 2mm can be a good predictor for the effectiveness an oral appliance for the treatment of OSAHS.