Indra Dental & TMJ Care Centre

 
     
  Think Neuromuscular :    An article presented by Dr. Rajesh Raveendranathan
 

Ever since I’ve started my neuromuscular practice, patients with headaches, neck aches, shoulder pains, etc., were treated using the latest technologies and cured appropriately. Orthopantomograms, Lateral Cephalograms, TMJ views of left and right TMJ’s with open and close positions, electromyograms of facial muscles, mandibular kinesiographic tracings, TENS applications and so on are the normal facets of the protocol that I follow. Using these, the physiological position of the mandible and accordingly the myocentric occlusion is recorded and appliances are made which would eventually relieve the patient’s pain.

But, why does all this happen? By doing this, we ensure that the condlye is in the most physiological position in the articular fossa. Dr. H.Gelb, in his research, divided the articular fossa into 7 parts. He then radiologically confirmed that the most physiologic position of the condyle is in the Gelb’s 4/7 position. Later research has shown that when the mandibular condyle is repositioned to the Gelb 4/7 position, the TMJ disk is recaptured to a normal position between 85% – 96% of the times. This correlation between the TMJ condyle repositioning to the Gelb 4/7 position and TMJ disk recapture has been proven by magnetic resonance imaging (MRI).

So, basically, getting the condyle into this Gelb’s 4/7 position is what all neuromuscular dentists eventually aim to do. Gelb also says that this can be achieved by mere palpation, in not so severe cases, by bringing the mandible downward and forward. This is especially true in cases of deep bites and lateral shifts. After doing a few cases by the book and as per protocol, I realized I’ve begun to THINK NEUROMUSCULAR.

With Gelb’s concept in mind, I completed a few cases THINKING NEUROMUSCULARLY. It was refreshing to experience this and I would like to share a very interesting case.

Case History

Chief complaint: This patient came to replace a crown on her upper right canine that had fallen off when she ate something. She also wanted to replace her other missing teeth with bridges. During routine oral examination, she presented with a posterior cross-bite on her left side and class 1 molar occlusion on the right side. On detailed examination, her labial frena were malaligned. There were spaces present between her lower anteriors. The upper right canine was already in contact with the lower canine during the clench, even without the crown. The dental midline has also shifted towards the left.

On further questioning, the patient said that she’s been having constant headaches and migraine attacks very frequently for the past 6 years. She’s been under medication for these head aches and has been suffering more in the recent past. She also disclosed that the crown on her upper right canine was placed 7-8 years back.

Inference: The last statement pulled the plug on her case. The crown on the canine might have been placed without clearing the occlusion. Every time she bit, her upper right canine got into occlusion first, hitting the lower right canine first and pushing the mandible to the left. This continuous lateral shift of the mandible towards the left, over the years, would naturally have caused her a great deal of TMJ dysfunction. And, hence, the headaches.

Treatment Regimen: Once the cause had been identified, the first line of treatment was to remove the bite of the crown from the occlusion. Then the abutments for the impending bridges were prepared. Both, maxillary and mandibular, posteriors were prepared in order to correct the vertical height equally. Otherwise, the impending freeway space would have had to be covered by only one segment, which means very large posterior teeth on that segment. Another reason to prepare both segments is to accommodate any cross bite that also we might incur during the bite registration.

As we can see in Fig 1, the upper right canine provides us the occlusion point during abutment preparation. There would be no requirement to have any further reduction of the upper right canine as the final bite of the patient is going to end up in an open bite.

The reason for this is the hyperactive tongue that is pushing upon her teeth. The open bite was all along hidden by the lateral deviation of her mandible. The spacing between her lower anteriors is also due to her tongue thrusting. This would have to be taken care of once the bite is confirmed and the bridges delivered.

Bite Registration: This is the most important aspect of any TMD treatment. Normally, as mentioned before, sophisticated softwares were used to determine the bite. But, when you start THINKING NEUROMUSCULARLY, our vision and tactile sensations along with our common sense would work as better ‘softwares’ for such cases.

As a start, we need to check the midlines as her lateral deviation is the most prominent occlusal defect. Most of the times, we check if the midlines of the patients’ upper and lower teeth are aligned or not. However, dental midlines cannot be construed as a proper bench mark for midline alignment. The apt anatomical landmark for midline correction is to check for the labial frena. The upper and lower frena need to be in line with each other. This is true in all cases except in malformed bone structures or other soft tissue deformations.

In this case, the lower frenum has understandably deviated towards the left in comparison with the upper frenum (that is attached to the stable fixed maxilla)(fig 2). We need to get the frena aligned. We ask the patient to start closing the mouth. Naturally, the mandible would move towards her normal left bite. We ask her to bite opposite to her normal trajectory, which is towards the right. We check whether the frena align or not when the first point of occlusion takes place. At this point, we seek the apt vertical height. This has always been the bone of contention. The safest method is to get the bite in such a way that her lower incisors are 1mm above the upper incisal edge. Minimal to zero overjet with 0.5 to 1 mm overbite is the optimum. Since this patient is an expected open bite case, we observe from the profile that the advancement of the mandible needs to stop once the two dentitions are almost end to end; care should be taken that it doesn’t go to a class 3 occlusion. The bite is recorded and transferred to model casts of the patient (figs 3, 4 & 5).

After articulation, the freeway spaces are noticed and bridges are manufactured in such a way so as to close this space. The bridges are then fixed (fig 6 & 8). The main problem that these patients would encounter would be their inability to occlude as per the new occlusion. This needs to be set right by providing them a convertible MORA or even just an inclined plane that helps guide their mandible into the required occlusion. What happens is that when the patient bites, the lower incisors would hit the tip of the inclined plane and slide into the grooves on the plane till they reach the required bite. This patient was given an inclined plane and was recalled after a month use (fig 7).

Post-Treatment: She came back after a month, head ache free. But she had a complaint that she couldn’t eat on one side. When checked, there was a slight open bite with respect to her left side (fig 9). This was closed by re-doing her left side upper bridge, which seemed to be the one that was deficient in vertical height. Once this was done, she was recalled again after 2 weeks to get familiarized with the new bite. This time she was asked to discontinue wearing the inclined plane.

2 weeks later, she was perfect with no aches or pains in her head or neck or shoulder. She could now chew with the new occlusion. Her labial frenal midlines were aligned. However, as we can see in Fig 10, her dental midlines need to be aligned. A host of other aesthetic problems needed to be solved. Her anticipated open bite due to her tongue thrust habit can now be seen full blown. Her lower anteriors needed to be moved towards the right and be given a tongue crib to curb her tongue thrust. She was now ready for aesthetic treatment.

As this case has shown, without the aid of sophisticated equipments, such simple cases of headaches, neck aches and shoulder pains can be relieved by ample manipulation of the mandible to achieve that precious myocentric occlusion. Gelb’s 4/7 condylar position in the articular fossa is the criterion.

My fellow dentists, just keep this in mind, we are more than just tooth doctors. As Dr. Jankelson says, “We dentists need to treat all the structures that are supplied by the trigeminal nerve. Only then will we be doing justice to our patients.” THINK NEUROMUSCULAR, BEYOND THE REALMS OF TEETH!

 

 


 
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