Step- by -Step Approach to Occlusal Equilibration
Glenn E. DuPont, D.D.S.
LEVEL III - Optimum Health
8. Maintenance Program
7. Other Elective Esthetic Procedures
6. Tooth Restoration
- provide a cleanable, shiny surface for
- strengthen weak teeth
LEVEL II 5. Bite Restoration
- even out biting forces
4. Gum Restoration
- reshaping of gums to make cleanable
Restore Mouth to Health – Restorative Dentistry
3. Bite Control
- diagnose bite needs – splint
- stop severe symptoms and discomfort – splint
LEVEL I 2. Infection Control
- effective brushing and flossing at home
- office cleaning of gums and teeth to remove
deposits and infection
1. Decay Control
- stop decay process
- clean out decay and fill teeth
- remove non-savable teeth
Disease Control – General Dentistry
I: Understanding the Temporomandibular Joint
We often hear dentists say that they “don’t want to get involved with TMJ problems”. Our position is that you MUST get involved with TMJ problems. It is not possible to ignore the TMJ’s and do acceptable orthodontics, or restorative dentistry, or maxillo facial surgery.
The Temporomandibular Joint is the fulcrum on which the masticatory system hinges. It cannot be treated exclusively while ignoring its interrelationship with other structural components of the masticatory system. Conversely, it is not logical to evaluate or treat dentitions as if the lower arch had no relationship to the upper arch . . . this relationship is determined by the condition and position of the temporomandibular joints.
The anatomy and histology of the temporomandibular joint MUST be understood. Without that basis, all diagnosis and treatment of masticatory system problems will be severely compromised. You cannot analyze what you do not understand.
HOW IS THE SYSTEM DESIGNED?
1. Boney framework
2. TMJ disc
3. TMJ ligament
4. TMJ capsule
5. Lateral Pterygoid Muscle
(Mahan, et al. JPD Nov. 83, Superior and inferior bellies of the lateral pterygoid muscle EMG activity at basic
6. Masticatory muscles
7. Dental occlusion
The masticatory system is precisely designed with direct anatomical and functional relationships. Individual change in a component of the system can affect the whole system.
Helpful readings: Anatomical Atlas of the TMJ, Quintessence 1991
Evaluation, Diagnosis and Treatment of Occlusal Problems, chapter 3
Temporomandibular Disorders, W.E. Bell Yearbook Med. Publisher
1990, chap. 1-4
LATERAL VIEW OF CROSS SECTION
1. Posterior slope of the eminentia (note typical convex contour)
3. Disk (note biconcave shape to fit both convex condyle and convex emintia)
4. Superior lateral pterygoid muscle
5. Inferior lateral pterygoid muscle
6. Synovial tissue
7. Retrodiskal tissue including posterior attachment of disk to temporal bone
8. Posterior ligamentous attachment of disk to the condyle
UNDERSTANDING CENTRIC RELATION
It is impossible to understand occlusion without first understanding the temporomandibular joint.
It is impossible to develop equilibrium of the masticatory system if maximum intercuspation requires displacement of the condyles from their physiologic, fully seated articulation. Thus occlusal analysis must START with the TMJ’s. If the condyles are not in their correct physiologic relationship when the occlusion is “corrected”, the occlusion will be harmonized to a malrelated condyle position.
CENTRIC RELATION is a dynamic relationship. It is an axial position, which means the condyles can rotate to open or close the jaw without moving out of the fully seated position in their respective fossa. Consequently, the mandible can be in centric relation even when the teeth are separated. Remember that this hinge axis can move down the eminence from the fully seated position permitting the jaw to open or close at any position from centric relation to most protruded.
Centric relation is the STARTING POINT. The condyles must not be restricted to centric relation, but must be free to move in and out of centric relation during function. Failure to permit access to centric relation during maximum intercuspation, forces the muscles to displace the condyles whenever the teeth are together.
CENTRIC RELATION is defined as “the relationship of the mandible to the maxilla when the properly aligned condyle disk assemblies are in the most superior position against the eminentia irrespective of vertical dimension or tooth position”.
At the most superior position the condyle disk assemblies are also braced medially, thus centric relation is also the midmost position.
A properly aligned condyle disk assembly in centric relation can resist maximum loading by the elevator muscles with no sign of discomfort.
Centric relation should not be confused with “centric occlusion” which refers to the jaw position during maximum intercuspation of the teeth regardless of whether the condyles are physiologically seated or not.
II: THE FIVE REQUIREMENTS OF
There are five requirements for stability. They must become a dominant factor in any occlusal analysis and every occlusion should be evaluated to see whether or not each requirement is fulfilled. The requirements must be used in sequence. They can be used for determining what problems exist or for deciding on what treatment is necessary. They apply to individual teeth or to the entire dentition.
The requirements for stability of occlusion are:
1. Stable stops on all teeth of equal intensity when the condyles are in centric
2. Anterior Guidance in harmony with the border movements of the
envelope of function.
3. Disclusion of all posterior teeth in protrusive movements.
4. Disclusion of all posterior teeth on the non-working (balancing) side.
5. Disclusion or non-interference of all posterior teeth on the working side, with
either the lateral anterior guidance, or the border movements of the condyle.
In establishing a stable occlusion, the anterior guidance assumes the key role. The anterior teeth are better able to resist lateral stress than the posterior teeth. This is so because of their mechanical position in relation to the TMJ fulcrum, and the muscle force.
Studies by Williamson and Mahan also point out that muscle activity is less intense if only the front teeth are in contact in excursions.
The anterior teeth also generally have denser bone around longer roots with better crown-root ratios.
In working with problems of occlusion, you will find that the difficulty of each problem directly relates to whether or not an acceptable anterior guidance can be established.
ANALYSIS WITH MOUNTED DIAGNOSTIC CASTS
The common use of unmounted casts or inadequate articulators is a baffling inconsistency, since the basic geometry it violates is so simple to understand and the error it produces is so substantial.
It is obvious we cannot open on one axis and then close on another axis and still return to the same position.
Since most centric relation records must be taken at an opened vertical to avoid interfering tooth inclines, the articulated casts must be able to close on the same arc to determine correct tooth to tooth relationships at the fully closed jaw position.
It is not enough to determine just the first point of contact. We must analyze the PATH of each tooth as it approaches and contacts its opposing tooth at the most closed position without displacing the condyles from centric relation.
Key point . . . Correct tooth-to-tooth relationships can be accurately analyzed only at the same vertical as the intended final intercuspal contact.MODEL WORK-UP
Check and verify accurate mounting
Mark first contact and compare to chart
Place WB onto models
Check for tooth – wax tooth
Open posterior latch, place articulating ribbon over condyles and see if pulls out as hold models into WB
Check amount and direction of slide and compare to chart
Mark hopeless, questionable teeth, and teeth that need to be crowned due to weakness or breakdown (from clinical and radiographic exam)
Unlock the centric relation lock and slide the cast together into maximum intercuspation or centric occlusion.
Drop the anterior guide pin down to contact the table on the front of the articulator and secure that in position.
Now place the cast back into centric relation and lock into place.
Close the cast together to the first tooth contact and observe the distance of separation between the pin and table anteriorly. This is the amount of room available for reduction to return to the vertical dimension of occlusion. Decide on the vertical dimension of occlusion you wish to work at.
Equilibrate all premature interfering contacts between teeth to return the pin to contact with the anterior table and to establish uniform centric relation stops all the way around the arch including the anterior teeth. We should now have uniform centric relation stops with a good cup fossa relationship on each posterior tooth and a stable holding contact on each anterior tooth. If not, consider sawing and moving teeth or waxing up to restore teeth. Be sure to create ideal anterior contours starting with lower anteriors.
Eliminate all balancing and working interferences by unlocking the centric relation lock and guiding the cast in left, right and protrusive excursions, marking with a red ribbon.
Lock the cast back in centric relation and mark with a black ribbon to read your centric relation stops which have been previously established.
Now eliminate all red skid marks that do not directly super-impose over black centric relation stops which you have established on all posterior teeth.
What remains should be only centric relation stops posteriorly and red guiding marks on anterior teeth.
Now harmonize the anterior guidance to establish a smooth gliding movement of the cast both left, right and protrusive. It is desirable to share this movement with as many teeth as possible anteriorly.
Be sure the anterior guidance is not too steep and the envelope of function not constricted or restricted.
You can now consider waxing up teeth in order to create ideal anterior guidance and esthetics being careful not to steepen the envelope of function.
Consider cross-over and any other habits as revealed by wear facets.
Once the anterior guidance has been harmonized, re-check for any posterior balancing, working, or protrusive interferences and eliminate those. Smooth anterior movements.
Since we want to visualize the end product, we are able to decide, through our model work, if we can successfully complete the case through equilibration or if we need to reposition or restore teeth to provide our requirement for occlusal stability.
III. INTRAORAL OCCLUSAL EQUILIBRATION
Be sure the patient understands the purpose and goals of equilibration are to provide a balanced occlusion in harmony with their system tooth contacts in centric relation and anterior guidance to protect the posterior teeth.
Load test again to be sure comfortable.
Sit the patient back and remind them of their first contact and slide.
Take initial Tekscan reading.
Begin to adjust to centric relation stops using a high speed handpiece.
Adjust upper and lower.
Develop cusp-to-fossa on posteriors.
Try to center along long axis, if possible, during initial part of this phase.
When anteriors first begin to hit (mark) in centric relation, then switch to a lower speed handpiece to be very careful not to lose stops.
When all stops look good in centric relation, then bimanually manipulate mandible and ask patient, “Do you feel any tooth touching before another tooth as I tap them together?”
Remove marks and adjust with slow speed if obvious. If not obvious and all marks look the same, adjust with rubber wheel until patient perceives all teeth touching together.
Check anterior teeth for fremitus and be sure you and the patient are not feeling any anterior teeth hitting before posterior teeth or any tooth moving.
Use slow speed or rubber wheel to adjust.
Be extremely careful when adjusting anterior centric stops to be sure you don’t go past V.D.O.
Remove all marks and re-mark centric relation stops with one color (black) and then mark excursion in another color (red) to remove posterior interferences in all excursions.
Use high speed handpiece
Check with “power” closure by having patient slide out and then “squeeze” back into the middle.
Check and refine anterior guidance for smooth lateral excursions and even protrusive excursions.
Use slow speed.
Look for “skips” in excursive marks.
Be sure to “open up” or “shallow out” anterior guidance, if appropriate.
Feel movements with bilateral hand position for smooth movements in all excursions.
Recheck posterior interferences in lateral and protrusive excursions.
Check for fremitus and anterior teeth in all excursions.
May need to “hold” teeth to check and mark if being moved.
Check bicuspids for fremitus in lateral excursions.
May need to “hold” tooth in and mark if being moved laterally.
Check with Tekscan for even intensity.
Sit patient up and ask patient, “Do you feel any tooth touching before any other tooth?” Then ask, “Do you feel the front teeth touching before the back teeth?”
If we get a response or fremitus where we feel the anterior teeth are hitting too hard sitting up, then we mark them sitting up and forward with one color (red) and then sit the patient back and mark in centric with another color (black). We can then remove or “open up” by grinding the first color (red) without touching the centric relation stops (black).
As a last step we will polish inclines, not centric relation stops.
Use rubber wheel on enamel or gold
Use porcelain polishing materials for porcelain.
The final instructions are to let the patient know the best thing they can do is to forget about their bite and we will check it at the next appointment. Teeth are not in cement and you can expect the teeth to shift. This is O.K. and normal. Our goal is to get the teeth in physiologic harmony with the patient’s system.
FIVE STEPS FOR HARMONIZING THE ANTERIOR GUIDANCE
Establish stable holding contacts on ALL anterior teeth
The mandible must be manipulated into centric relation and a stable stop established for each tooth so it cannot erupt past the point of contact. Attention to fremitus and constant prodding for patient feedback is essential to be sure these contacts are not too heavy.
Establish group function in protrusive
Since the incisal edges have already been determined, hollow grind the upper lingual surface as needed until the lower incisors maintain continuous contact from centric relation forward to the incisal edges of the upper anterior teeth.
It is not always necessary to have all four upper incisors contact in protrusive. In some patients, only the central incisors contact. Check for any new posterior interferences in protrusion.
Provide ideal lateral stress distribution on the anterior teeth.
The distribution of lateral contacts depends on the amount of periodontal support and the envelope of function. In a vertical envelope of function, cuspid protection may be acceptable. In more horizontal functions, lateral forces may need to be distributed over more anterior teeth. Using different colored marking paper, check for good lines in excursion with no skips. Feel for smooth transition and fremitus to teeth.
For working out anterior group function in lateral excursions, the working side condyle must be seated in its uppermost position while the mandible is firmly guided into lateral excursion. Check for any new posterior interference with “power check”.
Always remember . . . check each tooth in centric relation and all excursions for any mobility patterns. Check digitally, as well as with ribbon.
Provide horizontal freedom from CR if indicated.
Sit the patient up and forward away from the head rest and ask the patient to tap the teeth together lightly. Record these contacts with a fresh red marking ribbon. Then, keep the teeth separated and dry while the patient is leaned back and the jaw manipulated into centric relation. Mark tooth contacts in CR with a darker ribbon (blue or green). If the red marks from the unguided closure extend forward of the darker CR marks, extend centric relation contact forward the length of the red mark. DO NOT grind the centric relation mark.
The purpose of this procedure is to provide horizontal freedom for the front teeth of contact either in centric relation or slightly forward of it (protruded) without hitting into a steep incline. It is needed in about 50% of patients and rarely, if ever, requires more than .5 mm of forward freedom.
Before freedom from CR can be determined, all interferences to centric relation must be eliminated. There is no relationship between the freedom needed and the amount of slide prior to equilibration.
Always prod the patient with specific questions as to the teeth hitting with no one tooth or area hitting first. Also be sure the patient’s perception specifically is not the anterior teeth, even though they have a definite stop and grip the articulating paper. Give any post-procedure instructions.
MEASURING SUCCESS OF OCCLUSAL TREATMENT
Success at occlusal equilibration can be ascertained by the following four criteria:
1. Load testing is negative. Complete absence of any sign of tension or tenderness is an immediate and consistent sign of complete seating of the TMJs. If there is any sign of discomfort on loading, the inferior lateral pterygoid muscles have not completely released or there is an intracapsular disorder that was not diagnosed. Either sign is inconsistent with a perfected occlusion.
2. Clench testing is negative (empty mouth). A patient with a perfected occlusion should be able to clench with maximal muscle contraction with no sign of discomfort in either joint or in any tooth. This should occur as an immediate response following a perfected occlusion. If your patient can cause discomfort by clenching, the equilibration is not completed.
3. All occlusal function should be comfortable. A patient with a perfected occlusion should be able to move through all empty mouth excursions without being able to cause discomfort in either joint or in any tooth.
4. Occlusal stability. Occlusal stability is rarely achieved with a single equilibration appointment. Rebound of overloaded teeth is common and it is also possible to have some remodeling of intracapsular structures following occlusal changes. If the joint structures are sound, successful occlusal treatment should result in an occlusion that is stable for at least three months without any requirement for adjustment.
It typically requires about three appointments to achieve a stable occlusion but some patients may require more. The more complete the occlusal correction is at the first appointment, the fewer appointments will be required.
If an occlusal splint is used prior to equilibration of the teeth, the same criteria apply. Every occlusal splint should be tested for each of these criteria.
If the TMJs can accept loading with no sign of tension or tenderness, the clench test can be particularly revealing. If loading causes no discomfort but clenching does, it is a certainty that occlusal interferences to centric relation are still present. Empty mouth clenching or grinding should produce no symptom in either joint or at any tooth if the occlusion is perfected and the joints are healthy.