Occlusion: The “Science-Based” Approach

Dr. Dale makes many statements in his short article and cites the opinions of people with whom he agrees. He is pushing dentists to buy a set of electronic instruments with which they can recognize “physiologic harmony” of joint muscles and teeth, and then correct any disharmony they uncover using the same instruments. He repeats many of the claims that the manufacturers and their allies have made during the last decades of the 20th century:

• that elevated muscle activity “results from malocclusion-directed nociception” and that this can be detected with surface electromyography (EMG);

• that computerized mandibular kinesiology can be used to locate the “true mandibular rest position”;

• that electrical stimulation of the skin over the mandibular notch can be used to uncover “the myotrajectory for a peaceful neuromuscular occlusal position.”

He calls these methods an “objective, science-based approach,” but cites no scientific studies to back up the claim. He also decries the fact that academics have not embraced these instruments, and accuses us of having “an agenda” that is non-scientific. However, if he were to read just some of the articles that academics like me have written, he would find that our objections to the use of these methods are clearly based on science, and on a desire to prevent harm to patients. Consider the following.

• There is a great deal of evidence from well-controlled studies that EMG activity is not higher than normal in people who have pain in the masticatory muscle and joints.^1,2 Therefore, there is no reason to try to lower EMG levels to find the so-called “true mandibular rest position.”

• Computerized mandibular kinesiographs have been shown to be inaccurate and very difficult to calibrate in a dental office.^3,4

• Electrical stimulators used in the dental office activate the fibres of the superficial masseter muscle, not the masseter nerve.⁵ The so-called “neuromuscular occlusal position” is really a superficial masseter occlusal position.

None of the papers that are critical of this methodology are ever cited by the proponents of this instrumentation, except in letters which are sent to people like myself, and to deans and university presidents, ordering us not to publicize our findings. Dr. Dale uses the same approach when he implies that those who do not embrace the faith will be dragged into court. However, if the scientific evidence for and against the ideas that he has acquired were ever placed on the scales of justice, he would be surprised by the height to which his weighing pan would rise.

Dr. Lund is dean of the faculty of dentistry at McGill University and adjunct professor in the departments of physiology of the faculties of medicine at McGill and the University of Montreal.

References

1. Sherman RA. Relationships between jaw pain and jaw muscle contraction level: underlying factors and treatment effectiveness. J Prosthetic Dent 1985; 54(1):114-8.

2. Stohler CS, Zhang X, Lund JP. The effect of experimental jaw muscle pain on postural muscle activity. Pain 1996; 66:215-21.

3. Balkhi KM, Tallents RH, Goldin B, Catalina JA. Error analysis of a magnetic jaw tracking device. J Craniomand Disord 1991; 5(1):51-6.

4. Tsolka P, Woelfel JB, Man WK, Preiskel HW. A laboratory assessment of recording reliability and analysis of the K6 diagnostic system. J Craniomand Disord 1992; 6:273-80.

5. Dao TT, Feine JS, Lund JP. Can electrical stimulation be used to establish a physiologic occlusal position? J Prosthet Dent 1988; 60(4):509-14.