Occlusion

Dysfunctions

I have previously described the pain in TMJDS is due to muscle spasm and not stress and provided a logical explanation for its pathogenesis based on anatomy, biochemistry and physiology. It is a concern to me that stress as a cause of TMJDS is a persistent feature of UK dental teaching and practice, not least because our Oral and Maxillofacial Surgeon colleagues, to whom cases are often referred, have been taught during their higher training for the last 30+ years that stress is the cause. This is predicated on several papers by Harris and Feinmann, an Oral Surgeon and a Psychiatrist respectively. However they failed to examine the occlusion. To my mind, this must throw serious doubt on their conclusions and the continuing validity of such a blanket diagnosis. Their solution was the universal prescription of antidepressants which paradoxically may help as some have a spasmolytic effect on muscles too. As I know to my cost, if patients are in pain and no diagnosis is forthcoming, that in itself is stressful.

If you consider the pain is due to TMJDS, then there are additional question to add to my TMJ diagnosis list.

Ask you patient to answer further questions.

1. how severe is your pain on a 0 – 10 pain scale?
2. For how many hours per day are you in pain?
3. When during the day is the pain worst?
4. Show me on your face where the pain is worst using one finger only. This is most important.

Other tests include palpating the anterior border of sterno-cleido-mastoid and the upper border of trapezius, both of which may have sensitive trigger points in TMJDS.

If, when you auscultate the TMJ and hear a reciprocal click, that is a click on both opening and closing, this is a sign of a displaced intra-articular disc and is a case for early specialist referral.

During your treatment the pain levels can then be monitored and any changes recorded. You are looking for reductions both in severity of the pain and its duration. If there is no improvement in 6 to 8 weeks with the therapy you have provided, then you would be well advised to refer your patient for a second opinion when for example an MRI scan might be taken.

Classically TMJDS pain is unilateral and centered in the preauricular region over the mandibular condyle. Occasionally it may be referred post auricularly, typically the mastoid process or at the external auditory meatus. Other places include the submandibular or infra-orbital regions.

Palpation, where possible, of the muscles whose motor supply is the mandibular branch of the trigeminal nerve is one key to diagnosis. The four main muscles of mastication which embryologically are derived from the first branchial arch, are lateral pterygoid, medial pterygoid, masseter and temporalis, all of which can be easily palpated to determine if they are in spasm, and to what extent. The other first branchial arch muscles are anterior belly of digastric, mylohyoid, tensor palatae and stapedius. Most commonly master and lateral pterygoid are in spasm. Submandibular pain arises when there is reflex spasm in mylohyoid and the anterior belly of digastic on bimanual palpation.

Another trap for the unwary is those patients who principal symptom is pain in the external auditory meatus. They are most likely to have visited their general medical practitioner first when otoscopic examination will reveal no abnormality. They are then referred to an ENT Consultant, and may have an MRI scan which reveals no cause. What may be the explanation? The stapedius muscle to the middle ear, which has the trigeminal nerve as its motor supply (see 20 Answers) may reflexly also be in spasm.

Some patients point to the infra-orbital region and this has been diagnosed as atypical facial pain, again treated with antidepressants without examining the occlusion. I think atypical facial pain as a separate disease entity does not exist, and is a manifestation of TMJDS that has been missed. Why do I think that? I have seen 3 or 4 patients per year for 30 years with that presentation, and that is how my own TMJDS presented. Once I found a colleague who knew how to correct my deranged occlusion caused by a mandibular 3 unit bridge (see The ‘T’ Stop), my pain went and has never returned.

My own sign of a missed TMJDS diagnosis is as follows. The patient presents with unilateral facial pain. Various investigations have led to either one or more maxillary teeth, on the ipsolateral side, having been extracted or root filled, the first one in an attempt to relieve the pain, then the next after the pain continued. Why has this happened? The clinical examination has failed to palpate the muscles of mastication to determine if any are in spasm, Dawson’s manoeuvre to find the occlusion at centric relation and any premature contacts has not been carried out, and there has been a reliance on assuming, that because a tooth is tender to percussion, which commonly occurs if it is in occlusal trauma, it is pulpitis requiring a root filling. Root filling one fails to solve the problem, root filling two, fails also, and now you have the real diagnostic dilemma., Is the pain due to an inadequate root filling in a maxillary first molar where you failed to find and fill an MB2 or the original problem. Out with the forceps!

Having made the correct diagnosis, the first objective is pain relief. This is usually achieved by making an occlusal splint. This is normally fitted to the mandible, but for some Angles Class II div I patients a maxillary splint with an anterior bite plane will be indicated. The splint covers the deflective contacts and allows the muscles to relax, their blood supply will improve, and the products of anaerobic respiration be released into the bloodstream. The pain will subside. However, this splint must be made within the limits of the freeway space, and be reinforced with fibreglass mesh if it is thin in places. If this appliance exceeds the freeway space, it can induce a stretch reflex, and more muscle contraction. It is not surprising that patients discard such appliances.

Splints need to be very accurately made using maxillary and mandibular models with no blows (see Model Practice), taking a facebow record and a precentric occlusal record, that is one taken with the condyles in centric relation stopping just before any premature contact. After fitting it can be adjusted. The dentist uses Dawson manoeuvre to control the mandible whilst the dental nurse hold the articulating paper (see Demarcations). You should expect some early pain relief which can be monitored and recorded in the notes using the analogue pain scale and length of pain as described above. If you see your patient at two weekly intervals, as the muscle spasm relieves, the position of centric relation will change slightly. Again, check using Dawson manoeuvre and articulating paper as above. My own rule of thumb was, if there was no improvement in 6 to 8 weeks refer for an MRI scan of the TMJ’s. It just might be another problem.

If there is good pain relief, the temptation is to discontinue with the splint and hope the problem has gone away. Given that the problem is caused by an imbalance of the position of the teeth with the way the muscles of mastication are programmed by Nature to work, do not be surprised if the pain eventually returns.

The next stage is occlusal equilibration to correct the imbalances. Many dentists are frightened of this and some have been taught as undergraduates never to equilibrate an occlusion. I strongly disagree with that teaching. However, results with occlusal equilibration can be slow, whilst over-enthusiastic ‘grinding in’ can eliminate centric stops allowing teeth to over-erupt and tip etc, so compounding the problem and falsely suggesting equilibration does not work. The position of centric relation may seem to change. The reason is that there is still some muscle spasm and muscle guarding. As this gradually reduces, then the true centric relation may be found.

The method of occlusal correction is first of all to obtain centric occlusion at centric jaw relation. This means that your nurse holds the articulating paper whilst you, the dentist, manipulate the mandible using the Dawson manoeuvre. Do not allow the patient to bite together without this guidance. Only when then has been achieved should you move on to balancing the occlusion. This is where the BULL rule comes in, and for the working side ,grind buccal uppers and lingual lowers. In contrast, for the non-working or balancing side the palatal cusp is ground. The cusp to avoid grinding , if at all possible, is the mandibular buccal cusp, as this forms the centric stop and is the determinant cusp.

It is also quite common to find that a new crown or appliance causes pain because the occlusion is incorrect. Whilst some may subscribe to the Dahl concept that minor problems will settle with time, I cannot having had persistent problems that did not settle naturally. I recommend the following. Look at the occlusion with your new restoration out of the mouth (Fig 1), then with the restoration in place (Fig 2).

The two are not coincident, (a common problem when Kennedy class I dentures are relined). Equilibration is therefore required until the two do coincide, however long that takes (Fig 3).

I should like to add a few words about bruxism. Some authorities have described it as iodiopathic, that is to say it just happens. That may be the case, but before reaching that conclusion then a complete examination of the occlusion using the methods I have described above is advised. Over the years I have found that most of the bruxist patient I have seen do have occlusal discrepancies, often one ‘high spot’ around which their grinding has started as nature’s way to eliminate the problem.

Conclusions

TMJDS is a complex problem. It requires proper diagnosis to include checking for muscle spasm by direct palpation and learning Dawson manoeuvre to find the occlusion at centric relation. Saying ‘close or bite together’ will always give a false impression, and for dentate patients only shows centric occlusion, and ensures you always fail to determine the true state of affairs.

As dentists we need to work more closely with our medical colleagues. They have an inbuilt reflex from their training that unilateral facial pain equals trigeminal neuralgia. One group of London neurosurgeons claim that trigeminal neuralgia, which has many similar features to TMJDS, affects 1 in 200 of the population, but then they are not examining the occlusion either. It may be, but our role is to eliminate systematically any dental causes, and these are far more common.  It is salutary to remember that the normal practice when trigeminal neuralgia is suspected, of diagnosing it is on the history alone. I think this is a mistake, but how can we expect doctors to examine an occlusion when dentist are so poor at that clinical exercise.

Once a doctor has put a diagnostic label on a patient it is extremely difficult for a dentist to remove it. This pitfall may be illustrated by the following photographs of the worst case of occlusal error I saw in over 30 years. This patient was referred in by her GDP. She gave a history of left sided facial pain, diagnosed as trigeminal neuralgia for which she was taking increasing doses of tegretol, with little benefit, and to the extent that her daily living was being affected. Fig 4. shows her ‘bite together’ position – centric occlusion. Some teeth have been lost, others tipped and over-erupted. However, using Dawson’s manoeuvre her occlusion at centric relation is shown in Fig 5. – a massive discrepancy.

  

Centric occlusion  – Occlusion at centric relation

Her left lateral pterygoid muscle was tender +++ to palpation. The true diagnosis was TMJDS. However, her Consultant Neurologist refused to believe there was an obvious dental cause despite being sent copies of the photographs.

Atypical facial pain as a separate clinical entity is, based on my experience, almost certainly wrong. Again it is diagnosed on the history. Any suspected cases need an occlusal examination as detailed in the above notes.

For those who claim stress is the cause of TMJDS, again I challenge you to explain on a pathophysiological basis why TMJ pain is unilateral. The pain is caused by muscle spasm not stress. It follows that the key question to answer is why do the muscles go into spasm? For the record I have seen bilateral TMJ pain only 2 or 3 times in thirty years, but I have seen a right sided pain change to a left sided pain, and vice versa, with incorrectly made occlusal splints.

Finally, the only book written about occlusion that has ever made sense to me is the seminal work by Peter Dawson. If you are interested in the subject this is essential reading.