Abstract: A semi-custom intraoral discluder device for preventing chronic tension and common migraine headaches and temporomandibular disorders that are caused or perpetuated by chronic activity of the temporalis muscle. The discluder includes a trough, contoured to encompass at least one maxillary or mandibular incisor, from which extends a protrusion, typically of a dome shape. The trough can be retained on the teeth by any adaptable material which can flow around the teeth and then maintain its shape. The adaptation of the retentive material can be performed by the end user, health care provider, or anyone trained in the art. Once in place in the wearer's mouth, one or two opposing incisor teeth will come into contact with the protrusion prior to the upper and lower posterior and/or canine teeth coming into contact, regardless of the position of the mandible, thereby reducing the intensity of the activity of the temporalis muscle.