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Leading proponents of the Centric Relation theory of ideal occlusion react in various ways to the increasingly popular science of Neuromuscular occlusion. While some vehemently oppose NM as “bad science,” others simply state that CR itself is a neuromuscular approach. Virtually every NM dentist has studied CR, but very few CR dentists have studied NM. Every dentist is taught in dental school that some form of CR is ideal. Even though there are many different definitions of CR, each definition is a skeletal description of the condyle being seated in the fossa. So what’s the problem? Let’s look at CR with fresh eyes. Most of us first heard about CR in preclinical Removable Prosthodontics. Along with a rest position, CR was a starting point for building the occlusion. Then in preclinical Occlusion, we were taught to make occlusal adjustments on casts that were mounted in CR and we were taught how to make a CR splint.

The only real explanation we were given to justify the CR position was that it was stable and repeatable. Many positions of the body are stable and repeatable, including having your neck twisted to the point just before it breaks! The pertinent question to ask is whether or not the position is physiologic. And what about comfort? Shouldn’t comfort be a goal? In fact, shouldn’t comfort be the primary goal along with physiologic stability and repeatability? We were simply told by dogmatic authorities that CR is the most comfortable position, but where is the proof? How is comfort measured by proponents of CR? Shouldn’t relaxed muscles be the measure of comfort?

When you consider CR from a fresh perspective, do you really believe it is the most comfortable position? Have you tried placing your mandible into the rear-most, upper-most, mid-most position? Have you tried wrapping athletic tape around your head so your mandible is placed into that position when your jaw is tired to see if it makes you feel better? How do you think that position works for headaches or facial pain? The fact is that there is no stable and repeatable science to prove that CR is the least bit comfortable or physiologic. Unfortunately, CR techniques do not even utilize the latest in technology to ascertain CR’s purported stability and repeatability. Compared to NM methods, CR techniques are like pressing the doctor’s ear to the chest to check the heart when an EKG is available.

“Romancing the mandible” with its concomitant human error is an incredibly inaccurate way of finding a precise craniomandibular position, and there is no possible way of knowing if the mandible is closing on a physiologic trajectory without scientific monitoring of jaw tracking. CR’s methods are incredibly unscientific and would probably be dismissed today except that they are steeped in tradition. If CR were to be tested by its proponents, as it has been by NM proponents by measuring emg’s, jaw trajectory and stability, CR proponents would find out just how inaccurate their claims of stability and repeatability are. More to the point, they would discover the unfortunate fact that many patients who have been restored to CR are measurably uncomfortable, with extraordinarily high emg readings in the muscles of mastication.

What about other common CR topics? 1. How can the CR doctor find CR in a patient who has had a condylectomy? Many of these patients are fully functioning in physiologic bites. 2. Scientific jaw tracking equipment proves beyond any doubt that the hinge axis theory is erroneous; that, in fact, the jaw translates immediately upon opening. So how can any articulator possibly allow proper fabrication of a splint (or extensive crown and bridge work) by dropping the pin to open the bite? 3. Since teeth determine the position of the condyle in the fossa, any case that is built to CR should be stable. So why do many CR cases have to be adjusted into a “long centric?”

Could this be because CR is neither physiologic nor comfortable and that the patient naturally comes forward to a more physiologic CO? 4. If vertical dimension can predictably be increased in denture patients, why do CR proponents say it cannot be done with real teeth by using orthodontics or fixed prosthodontics? 5. Is there any real science behind centric relation, or is CR merely a tradition that has become a bad habit, based on old methods that could not be properly tested by today’s scientific advances? Principles of neuromuscular occlusion are in agreement with CR when it comes to eliminating interferences and finding accurate centric stops.

But occlusion has two components—the position of the jaw and the intercuspation of the teeth. Both components must be considered when building an optimal, stable, physiologic bite. Science overwhelmingly supports neuromuscular occlusion over the traditional dogma of CR. Dr. Bernstein is a Clinical Instructor at the Las Vegas Institute for Advanced Dental Studies. He has an exclusively cosmetic based practice in Piedmont, California, emphasizing complex larger cases, TMD, and oral conscious sedation in an environment of outstanding guest services. Dr. Bernstein can be reached at jbbdds@hotmail.com.