Why it is Important to Evaluate the TMJ Before Dental Treatment

Why it’s Important to Evaluate the TMJ before Dental Treatment?

Dr. Manminder Singh Sethi

Temporomandibular joint is the skeletal foundation of masticatory system. The temporomandibular joint serves primarily to allow movement and its secondary function is to provide a fulcrum upon which muscles apply force. During destructive changes in masticatory system TMJ remodels and adapts by disc displacements and also by arthritic changes.  Disc displacement is the quick response change in the TMJ during an imbalance in the masticatory system followed by more complex and difficult to treat arthritic changes. Moreover these changes in the joint are a progression, from simple disc displacement with reduction they progress into more complex disc displacements and finally into degenerative changes involving the bony parts of the joint.  There is a need to identify the pathology in the joint to identify the treatment plan and the long term prognosis.

Most patients who come into our operatory for reconstruction are with tooth structure loss, with or without any Oro-facial pain. Most of the wear other than erosion comes from the imbalance between various components of masticatory system.  Since the loss of tooth structure is the most apparent consequence a patient can see, he/she lands in our office. We dentists traditionally are tooth oriented.  We look at teeth and do a routine dental exam involving the teeth and its supporting structures.  Although some of us do a TMJ exam, it is very subjective and has a low success rate in evaluating the TMD’s. For a complex treatment like reconstruction we need to specify the reason/reasons for that particular situation in which the patient finds him or herself.

The concept of centric relation is the mainstay of treatment planning of both edentulous as well as dentate patients. The modern concept of centric relation is that the condyles should be in their most superior-anterior position in the glenoid fossa, that they are fully seated against the posterior slope of the articular eminence and that the articulating discs are perfectly interposed between the condyles and the eminentia, throughout the range of motion of the masticatory cycle.  Some authors term this as the orthopedically stable joint position.

The other concept of joint stability is that when condyles translate down the posterior slope of eminence the articulating discs follow the condyles. For normal TM joint function the disc assembly must be in perfect synchronization. In healthy subjects the working condyle (chewing side) moves posterior to the intercuspal position which may be 1mm or less, but in the case of joint disorders the condyle moves further posterior causing a direction of the force towards the retrodiscal tissue.  Since this area is highly vascular and is rich in sensory fibers, pain and discomfort are caused in the joint.  Muscles may become hyperactive causing further discomfort to the patient.  This may lead further to parafunction and a vicious cycle continues, leading to more tooth wear and so forth. The first step of dental reconstruction should be to diagnose the joint for long term asymptomatic function for the long term survival of new restorations. Without objective analysis of the joint function we clinicians cannot evaluate the true condition of patient’s joints when he/she comes to us.

So it’s very important to evaluate joint disorders and treat them, if present, before a prudent dentist moves further ahead into treating the dentition. Here I would strongly recommend reviewing Piper’s classification of temporomandibular joint disorders.

Methods used to evaluate the TMJ

1.        Patient complaint/history

2.        TMJ palpation

3.        TMJ Auscultation

4.        TMJ Imaging

5.        Joint Vibration Analysis

Research has proved the inadequacies of first three methods.^1-4 Imaging is subjective and only shows the morphology in two static positions; 1) at maximum intercuspation and 2) at maximum opening.^5-7 The Research Diagnostic Criteria for TMD has recently been called into question.^8-10  In contrast, Joint Vibration Analysis (JVA) works on the principle that if joint is normal, there is no rough surface there would be no vibration produced during function.  However, if there is rough surface among various moving parts of the joint they are bound to produce vibrations.  Since 1988 Bioresearch Associates, Inc. has developed their JVA system whereby one could analyze the joint vibrations during function.  And there is convincing evidence in literature about the accuracy and principle that it works on.^11-26

The sensors are placed over both the right and left joints.  (See Figure 1.)  Next, we need to measure the maximum opening of the jaw and any lateral deflection of the mandible at maximum opening.  The patient is asked to open wide and close and the opening and closing by the patient is coordinated by a metronome on the computer screen. The vibrations are transferred from the sensors and digitized by the computer software (BioPAK). The software converts this vibration data into waveforms.  (See Figure 2.)  Since most of the vibrations are in the opening half of the cycle, they are identified and analyzed. And with the help of a flow chart you can identify the joint disorder and treat it accordingly before proceeding to restorative part of the treatment plan.  (See Figure 3.)

The Clinical Importance of JVA in Reconstruction:  The Importance of Diagnosis

Diagnosis is important to devise a treatment plan and is important in all the three phases of treatment that is; pretreatment, during treatment and post treatment. Before we need to reconstruct teeth we need to identify what were the reasons for tooth loss.  Only then we can identify were we could end up with our treatment and achieve our goals. So it’s of prime importance that we evaluate and diagnose all the components of masticatory system which would involve. When there is disharmony between various components of masticatory system, each component of the system will try to adapt. Often the weakest link in this system breaks the first, and when patients come to you with loss in tooth structure (erosion being an exception), we can safely presume that there is remodeling in the joint, alteration in muscle function as well as changes in the mandibular movement pattern.

References;

1. Eriksson L, Westesson PL and Sjoberg H. Observer Performance in Describing Temporomandibular Joint Sounds. J Craniomandib Pract Jan 1987; (5)1:32-35.
2. Hardison JD, Okeson JP. Comparison of three clinical techniques for evaluating joint sounds. Cranio. 1990 Oct;8(4):307-11.
3. Paesani D, Westesson PL, Hatala MP, Tallents RH, Brooks SL.  Accuracy of clinical diagnosis for TMJ internal derangement and arthrosis. Oral Surg Oral Med Oral Pathol. 1992 Mar;73(3):360-3.
4. Yatani H, Suzuki K, Kuboki T, Matsuka Y, Maekawa K, Yamashita A.  The validity of clinical examination for diagnosing anterior disk displacement without reduction. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1998 Jun;85(6):654-60.
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