Two chronic health conditions are treated with oral appliances during sleep. One condition is temporomandibular disorder (TMD); a musculoskeletal disorder characterized by pain in the masseter muscle and temporomandibular joint. TMD pain is treated with a stabilization splint which operates by limiting abnormal muscle activity. The other condition is obstructive sleep apnea (OSA). Mild to moderate OSA is treated with a mandibular advancement splint (MAS) which holds the mandible in a protruded position to increase the pharyngeal airway space and reduce upper airway collapsibility.