Your Best Smile

Last Month I asked you to consider how you look at occlusal problems. Hopefully this created room for some new ways seeing and thinking about some of the conditions presented by your patients. This month I am going to suggest a different approach to evaluating occlusal problems that may simplify the diagnostic process and help direct treatment in a more logical and more importantly a predictable fashion. Most of this information is based on the teachings of John Kois, Functional Occlusion I & II: Science Driven Management (Courses II & VII)

What is disease?

Before I define health I would like to propose a way to define disease. Webster’s first definition for disease is uneasiness distress . This is followed with any departure from health; illness in general. It goes on to say a particular destructive process in the body, with a specific cause and characteristic symptoms; specific illness; ailment; malady. We can generally place dental disease into one of four risk categories:

In each of these risk categories there are a host of symptoms including pain, anxiety, sleep loss, inability to chew, bleeding gums and many more. These symptoms are helpful in making a diagnosis but thinking of dental disease in these four categories is a useful method for evaluating the significance of the patients concerns as they relate to disease.

The occlusion may contribute to all areas of dental disease causing restored teeth to fracture and periodontal pockets to worsen. Occlusal dysfunction also causes a common esthetic concern, short and badly worn anterior teeth. Diagnosing how occlusal dysfunction is causing damage to the oral cavity is key to properly treating the problem.

Diagnosing Occlusal Dysfunction

Many theories on occlusion are based in locating centric relation which has had many definitions over the years. Earlier definitions defined centric relation as the most retruded position of the condyle. Recently it has been defined as the most superior position of the condyle1 and even more recently the most superior anterior position of the condyle2.

Centric relation is currently defined as “the maxillomandibular relationship in which the condyles articulate with the thinnest avascular portion of their respective disks with the complex in the anterior-superior position against the shapes of the articular eminences. This position is independent of tooth contact. This position is clinically discernible when the mandible is directed superiorly and anteriorly. It is restricted to a purely rotary movement about transverse horizontal axis. “3

Fig 1 a and b Centric Occlusion: The occlusion of opposing teeth when the mandible is in centric relation. (CR is indicated by the alignment of the pink marks) This may or may not coincide with the maximal intercuspation

Centric relation is not a disease, nor is it a diagnosis. It is only a stable position that we can use as a point of reference when we are making a diagnosis. We can change the bite with orthodontics and prosthetics or surgery in more extreme cases. We know that muscles can change their size and shape, Think of body builders and ballerinas. It is more difficult to change the position of the condyle.

For instance when the bite has been locked in behind the front teeth as in a class II occlusion with a deep overbite I have frequently observed popping TMJ and reports of headache. It appears as though the guide path pushed the condylae distal to CR In fact roughly a third of my TMD patients fall into this category. Dr. Kois has referred to this case type as a Constricted Chewing pattern. Typically they will get tired muscles and they will exhibit more wear on the anterior teeth and often practically no wear on the posterior teeth unless they are very advanced in the degree of wear. When attempting to locate CR the initial point of contact will usually appear on an anterior tooth. If CR is located with the TMJ and related muscles completely deprogrammed the initial point of contact does appear on the anterior teeth. Some other keys to identify a constricted envelope of function is mobility on the anterior teeth, spaces between the anterior teeth and a lack of mobility on the posterior teeth.

Figure 2 a and b Maximal Intercuspal Position (MIP): The complete intercuspation of the opposing teeth independent of condylar position, sometimes referred to as the best fit of the teeth regardless of the condylar position. Also called maximal intercuspation or MI

The next level of occlusal dysfunction is the more familiar posterior interference into MIP creating avoidance patterns. These patients can be difficult to manipulate because the muscles will tighten up when any attempt is made to put them into CR. If you deprogram their TMJ and muscles of mastication they will typically have a posterior IPC. These cases can take longer to deprogram and be more difficult to treat. The bite needs to be repeatable on the deprogrammer to determine that the muscles have fully deprogrammed. If the bite wanders around on the discluding element the bite has not fully deprogrammed and the patient needs to wear it longer. .

Figure 3 a and b The NTI – tss Deprogramming appliance. The NTI is an effective deprogrammer but it is very bulky for daytime wear. This smaller diameter appliance might present a choking risk and should fit tightly onto the teeth.

Bruxism can sometimes be caused by interferences and problems with the occlusion. When it is, the bruxism can be corrected by correcting the occlusion. Other times the bruxism is independent from the occlusion and the cause may be unknown. It may be a sleep disorder or some other non-dental cause. These so far unstoppable bruxers can be identified by the horizontal grooves they grind into their deprogrammer. When you see these marks on a deprogrammer, you have strong evidence that nothing can be done dentally to stop this destructive habit. The best you can do is protect the teeth from the destructive forces of grinding by covering the teeth with some kind of bite appliance. The patient needs to be advised that he / she is likely to break and damage more teeth and porcelain in the future even if they do wear a night guard.

Figure 4 The Kois deprogrammer is a Hawley bite plane with a discluding element that contacts the lower incisors on one point.

Identifying the key elements of a healthy functional occlusion

For the patients who have constricted chewing patterns or posterior interferences there situation can be improved by equilibrating, orthodontically moving or prosthetically rebuilding the bite into proper function.

The anterior teeth must allow room for the mandible to move through its normal envelope of function without any constriction of the chewing pattern. If there is no bruxism, the jaw will be more comfortable with canine guidance to help it find maximum intercuspation. There needs to be bilateral simultaneous contact of at least the four corners, the canines and molars. All movements should be harmonious with the function of the TMJ as determined by a deprogramming appliance.

Conclusion

Many of the things being taught about the TMJ are partially correct. This leads to confusion and frustration with diagnosis and treatment. Because we don’t have all the answers there is a constant controversy about the right way to treat TMD and occlusal problems. It would be helpful if we could combine all of the information that is available on this topic and discover the best solutions for our patients. The human body is very complex, and there are so many factors involved when we are treating disease. Trying to come up with a one size fits all plan will limit our ability to provide the best treatment for every patient. I hope that this article provoked new questions and opened the door for a new way of looking at your cases. This is an invitation to examine the problems associated with treating occlusal dysfunction and to look at them from a different perspective hopefully resulting in new and better ways of treating occlusal problems.
Lynn A. Jones, DDS, RDH

Dr. Jones is a Graduate of the University of Washington, School of Dentistry and maintains a fulltime cosmetic dentistry practice in Bellevue and Seattle WA

1. Evaluation, Diagnosis and Treatment of Occlusal Problems, Second Edition 1989; Dawson, PE
2. Management of Temporomandibular Disorders and Occlusion 4rth Edition, 1998; Okeson, JP
3. The Glossary of prosthodontic terms 7th edition

The concept of occlusion and what constitutes a healthy bite is one of the most controversial subjects in dentistry today. Arguably the biggest disagreement among practicing dentists is how to determine Centric Relation (CR). Not only are there differing opinions on how to achieve CR, we are not even in agreement about what CR is or if it is even where the bite needs to be. The challenge does not come from the roughly 80 – 90 % of the patient population who seem to respond well to simple therapy using some kind of night guard or NSAIDs and muscle relaxers; it is the patient with a wandering bite that can’t seem to find one place to land, the chronic destructive bruxer, the mandible that becomes rigid when it is manipulated, or the intractable TMD case that causes frustration when the systems we were taught for diagnosing and treating the occlusion fail to work. The purpose of this article is to examine different methodologies for diagnosing and treating occlusion and TMD problems in a logical fashion in order to help the reader look at the evidence and decide if the methods they are using for diagnosing occlusal problems are effective and if there are some alternative techniques that might be faster, easier and more predictable for treating their patients.

What determines a healthy occlusion? Is it tripod occlusion on the cusps and in the fossae? Is it a level occlusal plane? Is it canine rise? Is it long centric occlusion? Is it having the condyle in the center of the fossa? Is it muscles that are quiet on the Myomonitor? Could it be any or all of these? How do you define health for your patients? How do you know when you have achieved success? How do you know when you have accomplished the goal? In this article I am going to answer some of these questions and suggest a different approach to managing occlusal problems and hopefully clear up some myths about occlusion.

What is disease? So often in dentistry we find ourselves treating symptoms that are not really disease. For example, I have overheard dentists saying that a case needs treatment with either porcelain or orthodontics because a patient has a “roller coaster occlusal plane�. The questions we need to ask ourselves is, “How well is the patient functioning with this “condition? Is it interfering in any way with their lifestyle? Do they have TMJ related symptoms like limited function, sounds, internal joint derangements or muscle pain? Do you see wear, erosion, decay, periapical infections, periodontal disease, bone loss, tooth loss? Is there pain? Does the patient have esthetic concerns? Is there a problem with speech or chewing? How old are they and how long have they lived with this condition? How likely is it to impact the future health of their teeth?

Ask any patient what they want and their answers generally fall into just a few categories.
1. They want to be comfortable, free from pain or any tightness and tenderness in the teeth and jaws. They want to be able to chew and speak without difficulties.
2. Many people are concerned about their appearance. They want their teeth to look nice.
3. They want safety or self preservation; they want to know that their teeth will last a long time without experiencing wear and tear, decay, tooth loss or damage of any kind.
4. When a patient is seeking treatment they want a sense of control; they are looking for a predictable outcome.

Fig. 1

Where is the evidence for bimanual manipulation? Are you certain that you have positioned the mandible in Centric Relation with bimanual manipulation? What evidence do you have that the patient’s mandible has been manipulated into CR? Can you demonstrate increased comfort? Can you show a reduction in the amount and degree of bruxism? Can you demonstrate that the condyle is in the center of the fossa? Are you able to visibly demonstrate less long term wear on the teeth? Do you know that the position of the joint is stable? (Fig 1)

Fig. 2

Where is the evidence for myocentric occlusion? Where is the evidence that this is health? Are �quiet muscles� desirable? Can you prove that you have treated all of the muscles of mastication? Are incisors supposed to be 12 to 14 mm long? Can you demonstrate that you have stopped bruxing? How do you know that the bite is stable? Can you show that the condyle is in the center of the fossa? Can you prove that there is less wear to the teeth? (Fig 2)

How can you determine a predictable outcome?

First you must make a proper diagnosis. That proper diagnosis must include information about what is causing damage to the teeth, periodontium or TMD In the first case on this page (fig 3a and 3b)the teeth show very little sign of wear and in fact this 40 year old woman had only tiny wear facets on her teeth. There were no abfractions, no periodontal disease, and no TMD, decay or tooth loss. The TMJ evaluation revealed a balanced and apparently stable occlusion. She did have tetracycline stains that had been previously removed and covered with composite fillings that were also starting to get dark. What are the occlusal concerns for a patient like this? Practically none- If this person is restored without changing her existing occlusion she is at very low risk of having any problems after the work is done.

Figures: 3a and 3b

These teeth are stained from tetracycline and old composite restorations. There is little if any evidence of occlusal wear in this 40 year old woman. The TMJ history and evaluation are negative making this a relatively safe and predictable case for managing the occlusion. The risk assessment here is low.

The second case (Fig. 4a and 4b) looks much more difficult to treat. it would be helpful to know if this heavy wear is caused by bruxism. After trying in a Kois deprogrammer* for a week, heavy horizontal grooves were worn into the discluding element on the Hawley bite plane by the lower incisors. Because the back teeth were not touching anything when the deprogrammer was in the mouth, it is safe to say that this person is a bruxer and that it is not caused by any kind of occlusal trigger from the teeth. The long term prognosis for this reconstruction is guarded making this a high risk case to treat. This patient bruxes and nothing is likely to stop the habit.

Figures: 4a and 4b

This 42 year old man is a non-stop clencher/ bruxer. He will destroy whatever dentistry you place in his mouth. He has had crowns, worn night guards, and a Kois deprogrammer . He has had his bite equilibrated and he has had Botox injected into his masseters. Nothing stops the habit. It appears to be of some origin other than dental. The risk assessment here is high.

The third case (fig 5a and b) appears to have severe occlusal problems. The posterior maxillary molars are supra erupted due to a lack of opposing dentition. The remaining teeth have only one vertical stop on the right first bicuspid. An attempt was made to create some vertical stops with platforms on the lingual of the incisors. What is the level of risk for treating this case and how do you know? Here are some hints: There is no wear on the night guard. There are no signs of abfractions nor is there any sign of periodontal disease except where the teeth have supraerupted. The patient does not have noise, muscle pain or locking and he is not aware of grinding his teeth. What he does have is a severe case of acid reflux. After seven years the restorations still looked like they were in excellent condition. Because the posterior teeth were never restored as planned, he did finally break the porcelain on tooth 28, his only true vertical stop in the entire mouth.

Figures: 5a and 5b

This 51 year old man has extreme erosion, a reverse smile, and missing lower posterior teeth all six molars and 3 premolars. He only has one vertical stop on the lower right premolar. He does not report any habits, he has a negative TMJ history and no signs of TMD. He does have a history of GERD and eventually needed surgery for a hyatal hernia. There are no habits, no posterior interferences and the only real occlusal problem is a lack of teeth. The risk assessment for occlusion in this case is moderate.

Conclusion: To develop a successful treatment plan that involves the occlusion, it is important to understand what is causing damage to the teeth and related structures and how to properly treat the occlusion. Rather than fulfilling the criteria of questionable dogma it is essential for dentists to understand the real goals of treatment that will lead to long term health, comfort and happiness for our patients and consequently for ourselves.

This is the first in a series of articles by this author to answer these and other questions about managing the occlusion.

*A Kois deprogrammer is a cross between a Hawley bite plane and an NTI device. The 3 – 4 mm wide discluding element is hidden behind the maxillary central incisors and is built right onto the bite plane. It is designed to take the teeth completely out of occlusion and have one contact point with one or two lower incisors on the discluding element. The molars are completely discluded with about 1mm of clearance.