The effect of oral appliances on polysomnographic outcomes has been extensively evaluated, and there is strong evidence of clinical benefit in controlling or significantly reducing the number of obstructive breathing events and arousals, and improving arterial oxygen saturation, particularly in the mild-to-moderate OSA range. The overall success rate is dependent on the definition used, with almost 70% of patients achieving a greater than 50% reduction in the apnea-hypopnea index (AHI) (19), and up to 50% achieving an AHI < 5/hour (12,13,21). Given that the aim of treatment is to resolve OSA, it is important that the more stringent definition of treatment outcome be used.
With regards to oxygen saturation parameters, studies have identified improvements in the minimum oxygen saturation, but rarely to normal levels. This is not surprising as, unlike CPAP, oral appliances do no inflate the lungs. With regards to sleep architecture and arousals, the data are less consistent, with only some studies reporting an increase in rapid eye movement sleep and reductions in the arousal index (12,13,21).
Less is known regarding the efficacy of TRD. Modest reductions in AHI (22), and improvements in minimum oxygen saturation and oxygen desaturation index (23) have been reported. Limited data suggest that supine-dependent OSA and absence of obesity are associated with a more favorable outcome (22).
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