This article from Dentistry IQ discusses the benefits to both CPAP and mandibular advancement devices (MADs) for sleep apnea.

The therapeutic effects of MADs on respiratory and subjective symptoms (e.g., daytime sleepiness and quality of life) when compared with those of CPAP were proven to be satisfactory in several randomized controlled trials, but before our study no randomized, placebo-controlled trials were performed that compared the effects of an objectively titrated MAD and CPAP on psychological distress symptoms. Therefore, the aim of this study was to compare the effects of a titrated MAD with those of nasal CPAP on psychological distress symptoms.

Our study was part of a randomized, placebo-controlled trial in which different treatment effects of a titrated MAD were compared with those of nasal CPAP and an intraoral placebo appliance. Sixty-four patients, with mild to moderate OSA and an average age of 52 years, were randomly assigned to one of the three groups (titrated MAD, nasal CPAP, or intraoral placebo appliance). All patients filled out a symptom checklist that was designed to measure symptomatic psychological distress over the prior week (e.g., depression and anxiety) before and after their six-month treatments.