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Temporal Mandibular Dysfunction is a relatively new area in modern dentistry.It has been complicated by the fact that many teaching institutions fail to recognize the importance of normal T.M.J. function. Many clinicians still feel that T.M.D. is essentially a psychosomatic condition primarily found in the menopausal female and should be treated with drug therapy and possibly a flat plane splint.
In reality, T.M.D. has been reported to occur in 35% of all children in America under twelve years of age.There is also abundant evidence in both the dental and medical literature that incorrect restoration and orthodontic procedures can complicate and even initiate severe T.M.D.
The objective of the presentation is to teach the clinician to first recognize and properly diagnose the various stages of T.M.D.Second, to stabilize the T.M.J.’s and eliminate the systemic side effects such as pain and vertigo.And third, to permanently stabilize the case with T.M.J. orthodontics, reconstruction, equilibration or a combination of these procedures.
Let us first address the question of diagnosis.All T.M.D. patients should be divided into two basic classifications.These are internal derangement cases and external derangement cases.The internal derangement case simply means that there is a mechanic problem within the T.M.J. capsule. The external derangement indicates that there is a problem within the muscle-skeletal system outside of the T.M.J. capsule. Another type of classification is intra-capsular and extra-capsular dysfunction.All external derangements are the result of internal derangements with the exception of problems such as an abscess within the muscle, direct trauma to musculo-skeletal complex, or neuro-muscular problems such as Meniere’s syndrome – these are unique situations that should be treated as independent problems.Therefore the side effects of most T.M.D. external derangement cases should subside when the internal derangement is correctly addressed.
At this point, it is appropriate to discuss normal T.M.J. function before we address any pathology. First, there should be no opening or closing deviations of the mandible. There should be no noise or pain when the mandible is extended through a full range of motion.Normal vertical opening should be at least 50mm from centric relation. Normal lateral excursion should be 12mm to 15mm per side when the skeletal midlines are correctly aligned at an edge-to-edge relationship of the incisors.
Internal Derangements
Internal derangements are sub-divided into two basic categories. There are self-reducing and non-reducing anterior displacements of the meniscus.The self-reducing anterior displacement of the meniscus means that as the patient begins to open their mouth the mandibular condyle is trapped distal to the meniscus relative to the articular surface of the glenoid fossa. As the patient continues to open, tension builds within the joint capsule. At some point in the opening process, then tension within the capsule is sufficient to point in the opening process, the tension within the capsule is sufficient to pull the head of the mandibular condyle into its correct position upon the meniscus. From that point onward, the T.M.J. function is normal because the condyle and meniscus are operating correctly as a unit.
There are two basic clinical observations that confirm the diagnosis of a self-reducing anterior displacement of the meniscus. First, there is an opening deviation of the mandible ipsy lateral to the joint problem.As the condyle relocates itself properly upon the meniscus, the mandibular deviation returns to normal.When the problem is bilateral, the opening deviation of the mandible is sigmoid deviating from side to side and returning to correct alignment, depending upon which joint complex returns to normal function first.
The second very diagnostic clinical characteristic is an audible pronounced sound within the joint capsule which usually presents itself as a “click”. This sound is generated by the mandibular condyle relocating itself correctly upon the meniscus.The earlier this “click” occurs the less serious is the damage within the joint capsule.So an “early” click will be much easier to treat than a “late” click. It is possible for the patient to develop a closing click, also called a reciprocal click.This noise is generated by the mandibular condyle sliding off of the meniscus and striking the genoid fossa, and usually presents itself as a dull “thud”.
The self-reducing anterior displacement of the meniscus will have a full range of normal motion. Very simply, at some stage in the opening cycle, one or both mandibular condyles return to their correct relationship with the meniscus, and from that point onward, function is totally normal.
The anterior self-reducing displacement of the meniscus is usually best treated with an anterior repositioning orthotic.These devices are commonly referred to as “pull forward splints” and can be placed on either the upper or lower arch depending upon the individual malocclusion. We shall discuss the details of the splint therapy later in this presentation.
If the damage to the joint complex continues, most patients advance into what is called a non-reducing anterior displacement of the meniscus. This means that no matter how hard the patient attempts to open their mouth, or manipulate their mandible, the mandibular condyles remain trapped distal to the meniscus.
The clinical ramifications are obvious.The patient will have an opening deviation of the mandible ipsy lateral to the problem with no return to a normal skeletal midline.They are usually able to obtain the normal 50mm or more of bite opening, but the opening is displaced obliquely ipsy lateral to the derangement. When the problem is bilateral, there is no significant opening or closing deviation of the mandible, but the patient will have limited vertical opening. This limitation will be less than the normal 50mm but not less than 30mm. This is very important because if the vertical opening is less than 30mm the patient is in the acute phase if an external derangement problem irregardless of the internal derangement.We will address this problem later in our discussion.
Another key diagnostic test is to align the skeletal midlines and check the patient’s lateral motion. There will be limited lateral excursion to the side contra-lateral to the non-reducing anterior displacement of the meniscus. The limitation of the lateral excursion is bilateral when the non-reducing displacement of the meniscus is bilateral. The limited movement is usually 5mm to 7mm.
There is no joint noise when the patient has the non-reducing anterior displacement of the meniscus since the condyle is unable to “snap” into its correct position on the meniscus. The joint noise has stopped. Therefore a patient who reports that their joint clicked at one point in time and has now stopped clicking has probably passed from the self-reducing into the non-reducing stage of the dysfunction.
The non-reducing anterior displacement of the meniscus is usually best treated with a pivot-splint. The pivot splint must be placed upon the lower arch. We will again discuss the pivot splint later in the presentation.
The most complicating factor in treating T.M.D. patients is the effect of the external derangement on the diagnostic procedure.Simply stated, the muscles attempt to keep the mandibular condyles correctly positioned on the meniscus when the patient is in full occlusion.When the malocclusion prevents the correct condyle relationship the muscles attempt to compensate the problem by trying to hold they condyle in its proper position.As they are unable to do so they can go into a condition of continued contraction know as a state of hyperactivity.The muscle primarily responsible for maintaining the correct condyle-meniscus relationship is the lateral head of the pterygoid.
Eventually other muscle groups, such as the massiter and the temporalis, attempt to assist the lateral head of the pterygoid and they also begin to undergo a state of hyperactivity. This condition when one muscle group attempts to support another muscle group is known as “muscle splinting”.This muscle splinting in turn can cause severe head, neck and back pain.
>This muscle hyperactivity, the external derangement, is always present as a result of the internal-derangement and usually remains at a chronic level clinically.This means that the patient can have any number of head and neck muscle sore and eliciting pain, but the muscles do not prevent normal mandibular motion.If the hyperactivity of the muscles become extreme, the patient passes into the acute phase of the external derangement.At this point the patient’s vertical opening is limited to 30mm of less. In most acute phase they cannot even separate their teeth.
The acute phase of the external derangement can occur at any stage in the internal derangement. It is sometimes seen at the very early stages of the dysfunction when the condyle simply slides on and off of the meniscus, to the extreme internal derangement that is non-reducing.This acute external derangement is primarily dependant upon the individual patient’s systemic physiology which includes oestrogen level, inter-cellular magnesium level and cell wall poisoning created by agents like nicotine and caffeine.
The acute phase of the external derangement creates a very difficult diagnostic situation. Since this condition can occur at any point in the internal derangement sequence, it can make diagnosis of the internal derangement impossible. The logical treatment procedure is to convert the acute phase of the external derangement to the chronic phase, then correctly diagnose the internal derangement.The flat plane splint is best suited to treat the acute phase of the internal derangement.This splint can be placed on either the upper or lower arch, and will again be discussed in detail further in the presentation.
Let us now discuss the sequence of T.M.D. and its treatment as it progresses from the child to the mature adult. In doing so, we will start with the typical skeletal class II – Division Two malocclusion which is the most common cause of T.M.D. This type of malocclusion holds the mandibular condyles back and possibly up depending upon the posterior vertical dimension.
In the early years of the disease the upper arch can be developed sagittally and transversely. This relieves the entrapment of the maxilla upon the mandible and the condyles spontaneously relocate into their proper position on the meniscus. This is known as “tracking”.This tracking can also occur on an adult T.M.D. patient depending upon the damage that has been created within the joint complex. Many clinicians treat a skeletal Class II – Division two by first developing the maxilla, which is the correct therapy, and they note the mandible moving forward towards a Class I relationship. They assume that the mandible is growing forward, translation, when they are actually observing the mandibular condyles tracking.
As the disease process progresses, the patient masticates with the condyles incorrectly pushed back on the meniscus.The smooth biconcave form of the meniscus begins to distort and erode. And, over a period of time, the mandibular condyles no longer track into their proper position on the meniscus.This condition is known as an anterior displacement of the meniscus when the patient is able to relocate the condyle on the meniscus the condition is self-reducing and is treated with anterior mandibular repositioning orthotic sometimes referred to as a pull forward splint.
The Anterior Mandibular Repositioning Splint
The A.M.R.S. can be placed on either the upper or lower arch. The construction bite is taken at an edge-to-edge relationship of the upper and lower incisors with a 4mm vertical thickness between the incisors.This routine mandibular position is sometimes modified through clinical experience, transcranials radiographs, and electro-myography, but it is a very practical starting position for most T.M.D. patients suffering from self-reducing anterior displacements of the meniscus.
The acrylic covering all of the teeth is fully indexed to allow the patient only vertical motion. This is an extremely important point. If the patient is wearing a pull forward splint, there should be no rotary motion of the mandible when the patient is in full occlusion. Any rotary motion will irritate the lateral head of the pterygoid muscle and make the external derangement more acute.
This is the point in the treatment when the use of muscle relaxants, hot and cold packs, and the Alpha-Stim can of great value. Anything that reduces muscle splinting, myofibril neuroalgia and hyperactive muscular contraction aids in the treatment of the external derangement. The key to using the pull-forward splint is to understand that the lateral head of the pterygoid muscle can pull the meniscus off of its correct position on the articular surface of the mandibular condyle. These muscles must be totally passive before the splint is adjusted to allow for rotary motion.
Sometimes the patient’s external derangement will not subside at the standard edge to edge, 4mm mandibular position. If this occurs, the clinician should increase the vertical dimension of the A.M.R.S. splint by approximately 2mm and the forward repositioning by 2mm. The re-setting of the splint should be made every 7-14 days until all external derangement has been eliminated. All of the side effects of the T.M.D. problem should have been totally corrected at this point in the treatment as well.
Once the lateral heads of the pterygoid muscles have become passive the full indexing is adjusted to allow for forward and lateral excursion of the mandible. The acrylic holding the mandible forward is not removed. Thus the patient can chew in a rotary motion in the A.M.R.S. with the condyles held forward and down in their correct relationship with the menisci.
Active therapy can now be initiated such as upper and lower arch development and the use of a reverse pull headgear. It is also possible to place a permanent orthotic at this point in order to stabilize the mandibular condyles.
The Pivotal Splint
The pivotal splint is used to treat the non-reducing anterior displacement of the meniscus. This orthotic should always be made on the lower arch and usually is nothing more than a flat plane splint.
The pivot is created by adding composite to the mesial lingual cusp of the maxillary first molar. This composite should be thick enough so that it is the only point of contact in the quadrant no matter how hard the patient bites. If the first molar is missing the second best point to create the composite pivot is the mesial lingual cusp of the maxillary second molar. Should that tooth be missing also, then the pivot can be placed on the lingual cusp of the maxillary second bicuspid. Should the patient be edentulous distal to the maxillary first bicuspid, an artificial pivot should be created in the area of the maxillary first molar by constructing some type of removable prosthesis.
If the non-reducing anterior displacement of the meniscus is unilateral the pivot is made unilaterally with the opposite side constructed with flat plane occlusion. The patient must eat in the pivotal splint until the displacement becomes self-reducing. At that point the patient is immediately placed into a pull-forward splint and treated in the appropriate sequence.
Sometimes the pivotal splint does not create a self-reducing anterior displacement of the meniscus. These patients require either manual manipulation of the mandibular condyles or surgery to secure the correct condyle-meniscus relationship.
The Flat Plane Splint
The primary use of a flat plane splint is to treat the acute phase of an external derangement problem. During this acute phase the muscles of mastication are in a hyperactive stage and prevent the correct diagnosis of the underlying internal derangement. The objective is to allow the acute external derangement to become passive so that the appropriate internal derangement orthotic can be fabricated.
The flat plane splint is usually best tolerated by the patient when it is placed on the lower arch. However, it can be placed on the upper arch when mechanics dictate. Minimum thickness for the occlusal acrylic is 1.5mm clearance between the most posterior teeth.
The splint should be adjusted so that all posterior teeth are in balanced contact no matter how the patient occludes. This allows the hyperactive musculature a chance to rest and become more passive.
If the flat plane splint is placed on the upper arch it is very critical that there is no lower cuspid guidance into the acrylic. This principle applies to any appliance on the upper arch that utilizes occlusal coverage of acrylic that has been adjusted flat plane such as a Schwarz appliance.
Sometimes the patient’s acute external derangement is so severe that they are unable to open their mouth to make an impression for fabrication of the splint. In this situation a temporary splint should be constructed chairside using the crown and bridge acrylic. As the treatment progresses and the patient gains more vertical opening, a more accurate flat plane splint can be made using models.
There are a number of clinical points that are critical for successful splint therapy. These include:
The general health of the patient is a critical element in the success or failure of T.M.D. therapy. Basic nutrition must include a daily multiple vitamin as well as 1,000 mgs. of Vitamin C twice a day, 1,000 mgs. of Vitamin E once a day and chelated magnesium.
In addition, the patient must eliminate all caffeine from their diet, limit their consumption of alcohol, and refrain from using any tobacco products. It is very important that the clinician assists the patient in making these changes in lifestyle.
Oestrogen plays a critical role in the patient’s ability to compensate for T.M.D. This is the reason the acute phase of T.M.D. is observed more frequently in the female patient. Oestrogen, via the parasympathetic nervous system, effects blood flow to the tempro-mandibular joints. This in turn reduces the patient’s ability to repair the damage caused within the joint capsule.
A lack of oestrogen effects cell wall permeability of magnesium. Magnesium is the trace mineral involved in the production of synovial fluid. Therefore the female patient experiences a dramatic reduction in synovial fluid which obviously means that the joints have less lubrication.
Reduced oestrogen levels lower the pain threshold of the patient and makes them more sensitive to discomfort. This results in the female patient’s reduced ability to tolerate the various side effects associated with T.M.D. Therefore, all female patients should be evaluated by their physician for oestrogen maintenance therapy.
Phase Two – Stabilization
Once all external and internal derangements have been resolved the patient is ready for phase two treatment, stabilization of the occlusion, the most common is T.M.J. orthodontics.
T.M.J. orthodontics usually involves three basic steps. First the arches must be properly developed to insure that all entrapment of the maxilla upon the mandible is totally eliminated.
The second step involves transferring the splint position to a finishing orthodontic appliance. This is typically accomplished by using an anterior bite ramp to hold the forward position of the mandible and composite build up on posterior teeth to support the vertical direction.
The third step usually entails the placement of fixed orthodontic appliances to finalize the occlusion to co-ordinate with the correct position of the mandibular condyles on the menisci. The third step is sometimes accomplished by using finishing splints that allow the teeth to passively erupt into their correct relationship. The severity of the malocclusion and economics must be considered when making a final decision on finishing the case.
The second most common solution to phase two stabilization is reconstruction. The same principles apply in that the mandibular condyles must be supported horizontally and vertically until the final fixed or removable reconstruction is placed.
A third option is a permanent splint. These are usually made of chrome-cobalt and are simply exchanged for the acrylic splint. The permanent splint is frequently the best option for the geriatric patient or when economics is the primary concern of the patient.
Sometimes the difference between the patient’s original occlusion and the desired final occlusion is very minimal. These cases lend themselves quite well to equilibration as a solution to final stabilization.
In some situations the patient’s original occlusion was not the cause of the T.M.D. problem. A classic example of this is the trauma created by whiplash injuries in automobile accidents. These cases are treated by using the same splint therapy to allow the joint complex to “heal”, then slowly removing the acrylic stops that are supporting the mandible forward and down. This technique is known as a “walk-back” procedure and must never be used if the patient’s original malocclusion was the underlying cause of the T.M.D. problem. The Tanner type splint is ideally suited for this walk-back technique.
It should be obvious at this point that correct diagnosis of the actual cause of T.M.D. is critical in its treatment. Minimal diagnostic records should include:
Additional diagnostic aids:
The clinician should have a very strict protocol that allows for thorough evaluation and diagnosis of each T.M.D. patient. The enclosed examination form is an excellent guide to successful T.M.D. therapy.
Summary
In summary, it is best to divide each T.M.D. case into three distinct categories. First, diagnose the external and internal derangements that are the cause of the problem. Second, select the appropriate orthotic to treat the problem. Third, stabilize the case in the appropriate fashion. Following these simple steps will allow the clinician to successfully treat the vast majority of patients suffering from T.M.D. and all of its related side effects.
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