Based on the predominant finding of intercondylar asymmetry, the mandibular midline will most likely deviate to one side or the other in protrusive transitory movement, rather than follow a straight midline linear plane. Devices that limit transitory movement to a midline
linear plane may not have a sound scientific basis. An alternative device to register the maxillomandibular relationship for intraoral sleep appliances was discussed that does not restrict normal biologic movement.
A prospective clinical study whose design directly tests the actual trajectory of unrestricted transitory protrusive mandibular movement appears to be indicated. A prospective clinical study that tests the clinical efficacy of the bite shims versus one of the devices shown that directs protrusive transitory movement in a midline linear plane also appears to be indicated.