Oral appliances therapy is becoming increasingly recognized as a successful treatment for snoring and obstructive sleep apnea(OSA). Compared with continuous positive airway pressure(CPAP), the gold standard therapy for OSA, oral appliance therapy are less efficacious for severe OSA but are more acceptable and tolerable for patients, which in turn, may lead to a comparable level of therapeutic effectiveness. Nevertheless, the various side effects of oral appliance therapy, such as, increased salivation or dryness, pain or discomfort in the teeth or gums, occlusal discomfort in the morning, temporomandibular disorders, dental and occlusal changes may cause discontinuation of treatment or changes in treatment plan. Therefore, oral appliance therapy should be provided by a qualified dentist who can evaluate oral tissues, occlusion, and temporomandibular joints, and prevent and manage the possible side effects.