Different types of oral devices have been used, making comparison between studies somewhat problematic. One-piece or two-piece construction, as well as adjustable vs fixed advancement capabilities, present opportunities for future investigations, and undoubtedly impact on tolerance, efficacy, and cost considerations. The degree of mandibular movement is also far from resolved, but may be as important a variable as the level of positive pressure delivered by CPAP. A majority of investigators15–17,23,26 have recommended at least 75% of maximal protrusion, a value representing absolute mandibular advancement of between 5 mm and 11 mm. One such study23 with an adjustable oral device even used an average movement of 88% of maximal protrusion (8.8- to 16.5-mm absolute advancement). Importantly, a substantial number of patients in that study achieved improvement despite severe OSA (mean AHI 52 ± 28/h for all patients), perhaps as a result of such profound advancement. Although the incidence of side effects was not detailed, another recent 2.5-year study27 specifically focusing on side effects instead of efficacy found only minor orthodontic and occlusive side effects despite initial anterior mandibular movement of 75% of maximal protrusion. Subjective discomfort was prevalent but relatively minor, and was outweighed by overall subjective improvement in daytime symptoms. It is possible, therefore, that the relatively lower degree of advancement achieved by the authors of this current study could be exceeded in future clinical trials. In so doing, an even better risk benefit ratio could be achieved, even with long-term use.