A prefabricated device intended to be used in the mouth during a prescribed period of time to stretch apart the oral opening to prevent and/or treat microstomia, typically acquired from facial burns, radiation treatment or surgical scarring. Also referred to as a microstomia splint or commissural splint, it consists of a small appliance with an intraoral stretching portion, and two extraoral protruding shafts which enable patient self-adjustment; accessories such as elastic and static bands may be supplied with the device. This is a single-patient reusable device.