The more sophisticated mouthguard designed for a person with a specific dental problem is usually called an occlusal splint or orthotic device.
An occlusal splint or orthotic device is a specially designed mouthguard for people who grind their teeth, have a history of pain and dysfunction associated with their bite or temporomandibular joints (TMJ), or have completed a full mouth reconstruction. An occlusal splint is custom-made using detailed study models on an instrument called an articulator that simulates the movement of the jaws. The occlusal splint is made from a processed acrylic resin and is designed to guide the jaw as it moves side-to-side and front-to-back. This precise custom orthotic device not only protects the teeth from harmful habits, but it supports the TMJ and the muscles that are used in chewing.
A recent innovation in occlusal splints/orthotic devices includes a specific modification designed to reposition the lower jaw allowing improved airflow while the patient is sleeping to aid in the treatment of sleep apnea.
The American College of Prosthodontists maintains a position statement on the Role of Oral Devices in Managing Sleep-disordered Breathing Patients.