In a perfect world, if a patient wears CPAP all night long and keeps it on in all body positions and uses it every night, it has higher efficacy than treatment with an oral appliance.  Since patient acceptance and compliance with CPAP is about 50% and patients often don’t wear their CPAP on a nightly basis, Oral Appliance Therapy may be equally effective.  Similar results in terms of health outcomes (sleepiness, quality of life, driving performance and blood pressure) suggest that although the two treatments have different efficacy and treatment usage profiles, the result is similar in overall effectiveness.

Patients often report preferring oral appliances to CPAP treatment, with better usage rates.

Dr. Sall recommends this article published in the Journal of Dental Sleep Medicine for a more complete discussion of the topic:

Efficacy vs. Effectiveness in the Treatment of OSA