A Clinical Protocol for the Removal of Balancing Interferences
Taking action to extend the longevity of restorative efforts
One of the goals of rehabilitative dentistry is to ultimately deliver an occlusal scheme to the patient with all the functional elements in place to assist in long-term success. However, even with the most detailed planning, occlusal interferences can occur in the mouth that were not seen or predicted in the laboratory phase of development. Finding and eliminating these interferences quickly helps ensure the patient’s initial comfort at delivery, minimize postoperative joint or muscular dysfunction, and aid in protecting the teeth and new restorations from potential fractures, attachment loss, or other pathologies in the future.
Balancing interferences in the functional occlusion of teeth have long been identified as being a cause of, or contributor to, numerous dental problems such as transient tooth pain, loosening of teeth, changes in postural muscle tension, chewing stroke patterns, and sometimes a clicking joint.1 As is the case with other less than ideal occlusal relationships, the significance of these mechanical interferences in the function of the masticatory system is greatly increased in the parafunctional patient.2,3 Parafunctional habit patterns coupled with balancing interferences can focus shearing forces on the inclines of molar or bicuspid cusps, and may lead to stress-induced fatigue fractures in teeth, craniomandibular muscular hypercontractivity and/or spasm, temporomandibular joint (TMJ) breakdown, and other orofacial maladies.4-6 Most clinicians recognize that balancing interferences are a hazard for natural teeth or implants, especially in parafunctional patients who may aggressively subject their dentition to these forces.7-9 This article will focus on clinical protocols that the clinician can utilize to help eliminate balancing interferences and the unwanted side effects that often accompany them.
Addressing Balancing Interferences
Whether a patient is receiving a single new restoration or full-mouth rehabilitation, the principles are the same. The dental team (dentist and dental technologist) strives to establish a stable occlusal scheme designed to provide a mutually protected occlusion.10 Posterior teeth should function under compressive loads and provide accurate centric stops in the presence of a stable TMJ. Accordingly, the anterior teeth should provide anterior disclusion to protect the posterior teeth from lateral and protrusive interferences and subsequent inappropriate shear forces. It is the shape and functionality of the anterior teeth that then determine the shape of the occlusal surfaces of the posterior teeth and the steepness of the cusps.
Even for the newly established, mutually protected occlusion, it is important to recognize that the occlusion is part of a biologically dynamic environment that is affected by time, overuse, tissue degeneration, and fatigue failure. Therefore, if the anterior teeth wear, the formerly protected cusps of the posterior teeth may move into a balancing contact that can ultimately create structural breakdown. For these reasons, it is critical to establish the etiology of wear at the initial evaluation and treatment plan accordingly to minimize a refractory process.
The clinical protocols for preventing or eliminating balancing interferences follow some simple, systematic steps to verify that the posterior teeth are free of excessive forces under heavy function. Below is a step-by-step protocol to verify that precautions have been taken to eliminate the potential for any balancing interferences during the planning and diagnosis, prior to delivery, at delivery, and post-delivery.
During Planning and Diagnosis
Beginning in the treatment planning stage, the following steps will help ensure occlusal stability in the long term:
1. Take an appropriate patient history of occlusal pathologies and parafunctional habits.
2. Examine the existing occlusal scheme and determine the necessary changes in the occlusion that will provide a more stable foundation for the new restorations. Utilize occlusal splint therapy when necessary to establish a verifiable stability.
3. Choose an appropriate restoration design for the individual tooth site and provide adequate reduction of tooth structure for the restorative material being used (Figure 1) (IPS e.max®, Ivoclar Vivadent, www.ivoclarvivadent.us).
4. Confirm that an appropriate solid centric occlusion has been established on the new restorations.
Prior to Final Delivery
Before the delivery of the final restorations, review the occlusal scheme with your dental technician to verify the setup of the instrumentation, ensure that all of the functional goals have been achieved on the articulator, and provide sufficient anterior disclusion to protect the posterior teeth. This step will also require that you have established a stable condyle disc relationship and that you have accurately recorded the angle of the eminence (Cadiax® Compact 2 Mandibular Recording Device, Whip Mix Corporation, www.whipmix.com) (Figure 2) and transferred this information to the articulator in the form of the condylar inclination (Artex® articulator, Jensen Dental, jensendental.com) (Figure 3).
If the restoration type will allow, place the restorations in the mouth to assess the occlusion and make any needed preliminary occlusal adjustments.
At Delivery
Once all restorations have been cemented or bonded, make an occlusal evaluation. Place one piece of blue articulating paper (Mynol® Articulating Paper Thin Blue Strip, ADA Products Company, Inc., https://adaproducts.net) on each side of the mouth and have the patient firmly bite down. Guide the patient’s jaw so that they firmly move into right lateral, left lateral, and protrusive excursive movements.
Next, place a thin articulating paper (AccuFilm® II Double-Sided Occlusal Marking Film, Parkell Inc, www.parkell.com) on the occlusal surfaces of the posterior teeth, instructing the patient not to bite down. Guide the patient’s mandible into a centric relation or fully seated joint position as appropriate and markings are made as the mandible is guided to closure. Make any needed adjustments to provide even solid centric contacts in the fully seated joint position.
Place a leaf gauge (Huffman Leaf Gauge, Huffman Dental Products, www.leafgauge.com) between the patient’s anterior central incisors and instruct the patient to move forward and backward. The leaf gauge will help guide the patient’s jaw into a fully seated joint relationship without any guidance of the mandible by the dentist. It is important that the process start with enough thickness provided by the gauge to disclude the posterior teeth. Once the patient verifies that no contact is felt on any posterior teeth when moving back and forward on the leaf gauge, the adjustments can commence. Each time a leaf is removed, instruct the patient to move forward and backward again. Any contact points showing interferences in the occlusion must be removed by the use of a fine diamond bur (Brasseler USA, https://brasselerusa.com) (Figure 4). This process is repeated by removing one leaf at a time from the leaf gauge until all of the posterior teeth are in contact bilaterally and at even pressures.
It is now important to activate the masticatory muscles to a level that is experienced during forceful closure or bruxing movements. Provide sugarless chewing gum (Biotene®, GlaxoSmithKline Consumer Healthcare, https://us.gsk.com) to the patient and instruct him or her to chew the gum until it reaches a normal chewing gum consistency. Position the gum on the occlusal surfaces of the right side of the mouth, and place a medium thickness marking paper (Mynol Articulating Paper Thin Blue Strip, ADA Products Company, Inc.) on the left side of the mouth after drying the teeth. Instruct the patient to chew the gum as normally as possible, pretending the marking paper is not in his or her mouth. The process of chewing the gum activates the oral musculature and reveals any mandibular flexion that may have been missed in more passive occlusal adjustments (Figure 5). After a few “power strokes,” balancing interferences become clearly visible so that they can be removed (Figure 6). After removing the interferences, repeat the marking process until all balancing contacts are eliminated during the induced heavy function.
After all adjustments are completed, it is critical to use an appropriate polishing system to re-establish the restoration surface finish to protect the restorative material from moisture degradation and abrasion of the opposing dentition (Lithium Disilicate Intra-Oral Polishing Kit, Brasseler USA). Polishing should follow the manufacturer’s recommendations for the materials used. Utilize magnification to assure that all of the fine diamond bur marks are removed (Figure 7 and Figure 8).
Post-Delivery
Finally, a protective occlusal splint (POS) often needs to be provided to the patient so that the new restorations and any remaining natural teeth are protected from nocturnal occlusal wear and damaging excessive forces from parafunctional habits. The ultimate design of the splint and amount of necessary stabilizing and follow-up adjustments depends on the relative stability of the organized occlusion and its many components. Even a finely adjusted initial occlusion can be altered by excessive parafunction, continued degeneration of the TMJs, drifting of unstable teeth, and other factors creating new balancing interferences as the restorations and natural teeth wear.
Summary
Balancing interferences in the occlusion may represent significant risk factors for the patient and should be removed in the susceptible patient and/or during restorative therapy. They can adversely affect hard tissues, muscles, ligaments, periodontal attachments, and other structures. Additionally, heavy parafunctional loads can ultimately result in catastrophic fractures from fatigue failure of the restorative material or tooth structure. The systematic approach outlined in this article, ensures that obvious or elusive balancing interference removal is achieved. Using these techniques can improve patient comfort and provide extended longevity to restorative efforts.
About the Authors
Cherilyn G. Sheets, DDS
Co-Executive Director
Newport Coast Oral Facial Institute
Newport Beach, California
Clinical Professor of Restorative Dentistry
USC School of Dentistry
Los Angeles, California
Private Practice
Newport Beach, California
Jean C. Wu, DDS
Educational Director
Newport Coast Oral Facial Institute
Newport Beach, California
President-Elect
Academy of Microscope Enhanced Dentistry
Private Practice
Newport Beach, California
Jacinthe M. Paquette, DDS, FACP
Vice President
American Academy of Esthetic Dentistry
Co-Executive Director
Newport Coast Oral Facial Institute
Newport Beach, California
Private Practice
Newport Beach, California
James F. Otten, DDS, FACD
Visiting Faculty
Newport Coast Oral Facial Institute
Newport Beach, California
Medical Staff in Department of Surgery
Lawrence Memorial Hospital
Lawrence, Kansas
Private Practice
Lawrence, Kansas
References
1. Clark GT, Tsukiyama Y, Baba K, Watanabe T. Sixty-eight years of experimental occlusal interference studies: what have we learned? J Prosthet Dent. 1999;82(6):704-713.
2. Posselt U. The temporomandibular joint syndrome and occlusion. J Prosthet Dent. 1971;25(4):432-438.
3. Liu ZJ, Yamagata K, Kasahara Y, Ito G. Electromyographic examination of jaw muscles in relation to symptoms and occlusion of patients with temporomandibular joint disorders. J Oral Rehabil. 1999;26(1):33-47.
4. Magne P, Belser UC. Rationalization of shape and related stress distribution in posterior teeth: a finite element study using nonlinear contact analysis. Int J Periodontics Restorative Dent. 2002;22(5):425-433.
5. Wang M, Mehta N. A possible biomechanical role of occlusal cusp-fossa contact relationships. J Oral Rehabil. 2013;40(1):69-79.
6. Eberhard L, Braun S, Wirth A, et al. The effect of experimental balancing interferences on masticatory performance. J Oral Rehabil. 2014;41(5):346-352.
7. Dejak B, Mlotkowski A, Romanowicz M. Finite element analysis of stresses in molars during clenching and mastication. J Prosthet Dent. 2003;90(6):591-597.
8. Palamara D, Palamara JE, Tyas MJ, Messer HH. Strain patterns in cervical enamel of teeth subjected to occlusal loading. Dent Mater. 2000;16(6):412-419.
9. Palamara JE, Palamara D, Messer HH. Strains in the marginal ridge during occlusal loading. Aust Dent J. 2002;47(3):218-222.
10. Okeson JP. Current terminology and diagnostic classification schemes. Oral Surg Oral Med Oral Pathol Oral Radiol Endod. 1997;83(1):61-64.
