For mild to moderate cases oral appliance therapy can be as effective and has significantly higher compliance rate.
Compliance yes. Effective, hardly universal. Oral appliance therapy is generally not as effective as CPAP head to head according to most studies.. It is considered a viable alternative for mild to moderate SA because of compliance rates and the idea that some therapy is better than none, however, although initial compliance rates are higher, studies have shown that as few as 32% of participants reported using their oral appliance regularly, and 55% stopped therapy within the first year so really little long term compliance benefit. Therefore cpap, assuming compliance is achieved, is still the gold standard of treatment for sleep apnea.