An intraoral device includes a one-piece, flexible, injection molded body made of a single homogeneous material. The body includes upper front and rear flaps, and lower front and rear flaps. Upper edges of the front flaps and lower edges of the lower flaps are sealed by respective upper and lower parts of a patient's mouth to form upper and lower evacuation channels when the body is disposed within the patient's mouth. Evacuation holes in the flaps are in communication with the evacuation channels. A connection section is in communication with the evacuation channels and is configured to extend outside of the patient's mouth to connect with a vacuum source for evacuating fluid from the patient's mouth through the evacuation holes and the evacuation channels.