Dawson's Occlusion: The concept of complete dentistry

Recently I have been reading a very good textbook: Functional occlusion from TMJ to smile design by Peter Dawson. I am attending a Dr. Michael Melker's Occlusion lecture in August and thought it would be good to do some prereading into the subject. Occlusion and the TMJ is one of many things that are notoriously poorly taught at dental school but are so important to everyday practice. We have to ensure that treatments we are performing on patients are doing benefit and not harm. We have to ensure that we are working towards stability of the orofacial complex and not instability and as patients are even less educated than we are on the subject, we have to take responsibility for our actions because their is a certain level of trust on their part that we should not discount.

The concept that Dawson introduces in his textbook is that of "Complete dentistry". It is in essence what some would extend and call call "Holistic dentistry". He urges us to not focus on one part of the orofacial complex i.e the dentition and to consider it as a whole with interrelated and connected parts. The aim of any occlusal therapy is harmony and peace of the neuromuscular system. We cannot consider one part of the orofacial system as healthy unless they are all healthy as instability in one component will inevitably lead to the breakdown of other components. He considers all dental disease as progressive and that it will continue to worsen if not treated early. It is essential to be a master of what you are doing because although the signs of early disease are subtle, they should be easy to spot if you are vigilant and educated. We cannot convince patients of the need for early treatment if we cannot make them see the consequences of nil treatment and so we must be able to see these ourselves.

Dawson has 7 goals for any occlusal therapy:

1. Freedom from all disease in masticatory structures
2. Maintainable periodontium
3. Stable TMJs
4. Stable occlusion
5. Maintainable healthy teeth
6. Comfortable occlusion
7. Optimum esthetics

Achievement of these goals ultimately leads to harmony in the TMJ and dentition as well as a peaceful musculature. He goes on to explain that there is method in the madness of dental and orofacial anatomy. He treats this complex structure extremely structurally and explores how one would design the perfect system for mastication and how that relates to our design. There is a purpose for every contour and shape of the teeth and TMJ and in occlusal therapy, we should do our best to fit into the form of nature. 

There is always cause and effect in pathologies i.e there is a reason any system breaks down. Treating the effect i.e symptomatic relief without addressing the cause is rarely a successful outcome and is not needed.

We must begin treatment with the end in mind. Dawson outlines his 7 tests for treatment success:

1. TMJ loading test is negative: The TMJ must be comfortable in loading. If this fails then it is likely that the condyles are being braced by the lateral pterygoids  or there is an intracapsular disorder. If the TMJ is unstable or uncomfortable than it is considered a treatment failure.
2. Clench test negative: With the patient clenching hard, there should be no discomfort in teeth or the muscles. Tooth pain indicates a  premature contact or deflective interference and muscle pain indicates myofascial imabalance.
3. Grinding test: Posterior teeth should ideally only contact in centric relation. When the patient grinds away from the centric relation position, the posterior teeth should disocclude. This disocclusion causes elevator muscle deactivation except for the anterior temporal muscles. Where there is no anterior contact in CR e.g in class 2 occlusions, working side group function may be necessary and the aim is comfort in excursions in working side group function. Abberant posterior contact will result in excessive posterior wear and muscle hyperactivity
4. Fremitus test negative: placing a finger on the labial surface of the anterior teeth and getting the patient to clench and grind their teeth. movement of the anterior teeth indicates fremitus and suggests a restrictive envelope of function or failure to provide a "long centric"
5. Stability test postitive: A stable TMJ and dentition implies that there will be no need for treatment adjustments for at least 3 months. This may take some time to achieve due to the rebound of teeth and TMJ condyle remodelling. This stability may be impossible if the damage to structures is too extensive. Then the aim is for "manageable stability"
6. Comfort test positive: the patient should have comfortable, teeth, lips and face in function and speech. Any discomfort indicates the need for adjustment
7. Esthetics test positive: Patients are often but not always more accepting of esthetics than operators. Functional harmony is dependant on anatomic harmony and that which functions optimally has been shown to have ideal esthetics. Therefore, to a certain extent, following the anterior functional matrix theory makes esthetics an objective decision.

The next part will explore occlusal pathologies and causes of these.