Oral appliances (OAs) are a primary treatment option for snoring and mild to moderate obstructive sleep apnea (OSA) and are implemented as a noninvasive alternative for patients with severe OSA who are unwilling or unable to tolerate continuous positive airway pressure for the management of their disease. Studies have demonstrated the ability of OAs to eliminate or significantly reduce the symptoms of OSA and produce a measurable influence on the long-term health effects of the disease. Most studies have evaluated one type of OAs, the mandibular advancement splints. This article describes the effectiveness and outcomes of mandibular advancement splints.