The Reasons Neuromuscular Dentistry Doesn't Work
William G. Dickerson, DDS, FAACD
In an effort to defuse the excitement over neuromuscular dentistry, several occlusion guru's have given lectures, written articles and done interviews extolling the reasons why it won't work. I've compiled a list of them and want to discuss each one with the readers. Understand that there is so much science behind NM dentistry that my comments almost do the cause injustice. But in an effort to not bore the reader and to make this a readable article (length wise), I will not spend a lot of time with that aspect of the defense. Regardless, here are some reasons that have been mentioned why NM dentistry doesn't work or is wrong.
1. Using a TENS unit to find the physiologic rest position of the mandible doesn't work as it relaxes all the muscles EXCEPT the lateral pterygoid.
First of all, this is physiologically impossible. Since the stimulation is neurally transmitted (via the V and VII cranial nerves), there is no way it would bypass one muscle innervated by these nerves and even less possible that it would make that one muscle go into spasm as suggested by these statements. Understand that it has been proven to be neurally (not surface) stimulated by the administration of succinyl choline. When administered, the pulsing stops. If it were surface stimulated, the pulsing would not stop.
The reason they make this statement is because they don't understand physiology and assume that it's the only way the mandible will come down and forward. Yet by relaxing and lengthening ALL the muscles, gravity will bring the mandible down and forward. Muscles are not sticks, bones or hard objects. They are more like string than sticks. Therefore the position of the mandible is determined by the angle of all these muscles and what happens when they are relaxed. Imagine someone sleeping sitting up. Do they sleep with their mandible in CR? Of course not. Their mandible comes down and forward.
2. Neuromuscular dentistry doesn't work because the most comfortable position is CR.
I've heard this statement by many doctors, yet no one can show me proof of this. There is no study to confirm this statement. In fact, when we did a study to determine this statement, 17 out of the 18 subjects were the most UNCOMFORTABLE in CR. One had higher muscle hypertonicity in CO. But all were the most comfortable in a neuromuscular position. Like the old commercial, "Where's the beef". It's easy for an expert to make a statement and his or her followers to believe what they say as gospel, but there is no study that will confirm this statement.
3. Neuromuscular dentists are having temporary success because any orthotic that creates cuspid guidance will work.
I have now seen three cases where someone was put in an appliance (CR created) where I tested the comfort of their muscles using EMG's. In none of them were the muscles comfortable. When the orthotic was made using the NM position, the muscles immediately calmed down and they experienced immediate relief. An orthotic does not just work because it provides cuspid or anterior guidance. It works because it is designed to the most comfortable position of the mandible.
As far as temporary success, how does one define temporary? Bob Jankelson has a patient that has been temporarily relieved for the last 35 years.
4. NM dentistry and leveling the occlusal plane is not important because the mandible rotates for 20mm in a pure hinge manner.
This is based on Posselt's diagram from 1952. In fact, CR is based on this theory. The problem is that he was demonstrating "border" movements, not physiologic movements. A study done in Italy and published in Journal of Oral Rehabilitation, 1996, June: 23(6):401-8, showed this myth is simply not true. They used a kinesiograph on 28 subjects and in none of the subjects was there any pure rotation, not even in the first millimeters of movement. Rotation and translation were always combined and they concluded, "The results show that the hinge axis theory cannot explain the mandibular movements because a pure rotation does not occur around the intercondylar axis."
The truth is you can feel this on yourself. Place your little finger in your ear and feel the condyle move as soon as you start to open. The proponents of the pure hinge will say that is because you are feeling the lateral pole, not the medial pole. They can say this because you can't stick your finger in your ear and feel the medial pole. But place your finger under your ear and feel the back of the neck of the condyle. If you opened in a pure hinge, you would feel the mandible pinching your finger as it moved back. Instead, your finger falls into that space as the neck of your condyle moves away from the finger, indicating an immediate translation.
5. Neuromuscular dentistry won't work because you can bite stronger if the condyle is seated in CR. After all, imagine a nutcracker.
The problem is that the TMJ is not a nutcracker. In fact, it's not a hinge movement at all as demonstrated above. But where is the strongest position to bite? The result of any therapeutic position should be an improvement in muscle function. I don't think many would disagree with that. Hickman did a study comparing three different positions, CR, Leaf Gauge, and Neuromuscular. Their conclusion, "With respect to balance and activation, a neuromuscular condylar position proved to be the position capable of recruiting the greatest motor unit activity and muscle recruitment."
Even Ash and Ramfjord said, "All scientifically controlled tests with telemetry, electromyography and clinical measurements have conclusively shown that if occlusal guidance to CR is eliminated, the patient will naturally function and be able to exert the heaviest bite force anteriorly to centric relation."
Possalt himself said, "Optimal occlusion function when biting together is better when slightly forward to CR." If the CR hero's themselves agree that the best position for function is a down and forward position, who are we to argue.
6. The Neuromuscular position is not desirable because you CAN bite stronger in that position and you don't want a good bite to protect your restorations.
Just the opposite of some of the occlusion experts, at least one CR advocate is lecturing his belief that the NM position is not desirable because it DOES create a stronger biting force. This is something he says is undesirable because it will create a greater force on his restorations causing breakage. I just mentioned in the exact opposite argument some are making above, that the result of any therapeutic position should be an improvement in muscle function. This goes against the objective of any medical treatment done by any specialty. If your arm is broken, would you want them to restore it to a position of weakness? If you had an artificial joint placed, would you want them to make your arm weak to protect the joint? It's silly.
The truth is that I have very few restorations that break in the posterior. If one of my restorations break, it generally is in the anterior because of an interference. Yet the greatest force is applied in the posterior. If I need the strength to bite into something, I want to make sure it's there. It's called optimal muscle function. It's a desirable result for any treatment.
7. It's best to place someone is CR because if they sleep at night their teeth will fall back into that position and all the teeth will touch. But during the day if they want to come forward, it won't be as bad because less force is applied if only the front teeth touch.
This one amazes me. First of all, you don't build a bite with the assumption that someone MIGHT sleep on their back. But if they are comfortable and their mandible is at rest, the teeth won't come together. And if someone wants to be forward during the day and they have these anterior teeth that are hitting, it's exactly why more breakage occurs on anterior teeth than posterior teeth. If the teeth were built to the NM position, the muscles would be comfortable, the patient would not brux and little damage would be possible. But what this illogic is saying is, sacrifice the day comfort and chewing efficiency because they MIGHT fall back if they sleep at night. Our contention would be that if they are comfortable, then their teeth won't be together and for those very few that this might apply to, make them a nighttime appliance.
8. If you relax the muscles then they might atrophy.
This was said by someone that teaches at a CR training institution. Not only is this illogical since the person will be talking, chewing and swallowing all day, stimulating the muscles, it flies in the face of what you want to accomplish while you sleep. It is desirable to have all the muscles relaxed during sleep. Do we then tell our patients not to sleep so their muscles won't atrophy? Of course not. This argument to me is more of a desperation at salvaging their expertise and indication that they are searching too hard for reasons to dispel the logic behind NM dentistry.
I want to make sure everyone realizes that I understand this defensive posture. These people have gone out on a limb blasting NM dentistry for years. They don't understand it as none of the people making these statements have ever studied it. They may claim they have, but they haven't. But they have backed themselves into a corner and no one wants to be wrong. Many have spent their lives saying these things and it is very difficult for them to now say they were wrong about something. I've personally invited many of these guru's to come and hear for themselves yet they all refuse to even listen. In my opinion, it shows me they are afraid they may be wrong and don't want to hear it.
Now when you hear someone make these statements, you'll know the truth and illogic of what is being said.
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