The seminal hypnosis study by Kroger and Schneider in 1959 prompted more research along hypnosis lines. Shortly thereafter VE was used as an analgesic for gastro-intestinal surgery, where it was found that over 90% of patients entered useable levels of trance induction prior to surgery (22). The Sadove study caught the interest of the dental profession, which was awakening to the role of anxiety in temporo-mandibular joint (TMJ) and myofascial pain dysfunction and during dental procedures. TMJ dysfunction is an affliction that affects many people. In order to understand the scope of the VE studies with TMJ, it is important to have a deeper understanding of TMJ dysfunction and myofascial pain dysfunction.

Two theories exist as to explain the origins of bruxism, TMJ dysfunction and myofascial pain dysfunction (MPD), a condition involving severe pain in facial regions. The tooth-muscle theory ascertains that disharmony in occlusion produces altered proprioceptive information that activates the occlusal pattern generator which activates the masticatory (jaw-closing) muscles, which in turn grind down the dentition until a satisfactory occlusion is reached (14, 20, 12). Certainly, many people can recall a time when a poorly made dental filling or orthotic has activated this response, quickly resulting in jaw tension and pain. The psychophysiologic theory implies that emotional factors such as stress and anxiety manifest in increased muscle tension (14, 12, 20) and increased perception of pain (4). It has also been shown that all people show high levels of masseter tension during initial exposures to a stimulus-response task (30).