Occlusal interferences and temporomandibular dysfunction abstract

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Disagreement exists regarding the relationship of occlusal interferences and temporomandibular joint dysfunction (TMD). This study attempted to determine what affect developing a uniform contacting balanced occlusion, in centric relation, would have on signs and symptoms of TMD. A randomly chosen group of 60 patients with occlusal interferences and signs and symptoms of TMD had their occlusions balanced at centric relation by means of a mandibular orthotic. There was a 95% significant reduction or elimination of chief complaints of TMD when symptomatic patient's occlusions were balanced in centric relation. This data suggests a relationship exists between balancing occlusion in centric relation and

optimum management of TMD.

A historical perspective is useful to understanding the disagreement that exists regarding the affect, if any, of occlusal interference as an etiological factor for temporomandibular joint dysfunction (TMD).
Over time several etiologies for TMD have been described in the dental literature [1,2]. Psychological stress [3-5], trauma [6-10], occlusal interferences [11-33] and parafunctional habits such as bruxism and clenching [1,3,11,15,34] have been described as etiological factors. However, there appears to be lack of agreement as to the relative significance [1,35-38] of these factors.
A number of studies have indicated occlusal interference is not a factor in the development of TMD [1,34,36,39-45]. However, numerous reports, as well as consistent and persistent anecdotal clinical experiences, continue to support the position that occlusal interference does in fact play a primary role in the development of TMD [10-33,46-48].
This dichotomy is further compounded by patients who have occlusal discrepancies and no apparent symptoms of TMD, while other patients, having similar occlusal disharmonies, develop significant TMD symptoms. This creates a real dilemma for the practitioner who intends to restore a patient's stomatognathic apparatus to improved functional health.
If occlusal imbalance is a primary factor in the development of TMD then occlusal reconstruction could become quite problematic if such reconstruction is developed in the presence of a symptomatic temporomandibular joint (TMJ). This is especially so when each patient's unique emotional and physical variability may also be significant considerations in a multifactoral milieu.
The purpose of this study was to determine the affect of developing a balanced occlusion in patients showing signs and symptoms of TMD as a consideration in phased treatment of the problem.

A general patient population of approximately 300 patients, seeking relief from signs and symptoms of TMD, was given a specially designed questionnaire and a computer graded commercial "TMJ Scale" questionnaire [49-52] (Pain Resource Center, Durham, NC). Each patient was also evaluated by means of a complete dental examination, full-mouth intraoral radiographs, head and neck muscle and TMJ palpation, ranges of jaw motion, mounted diagnostic casts, occlusal analysis, corrected TMJ tomograms and TMJ stethoscope and Doppler auscultation (Teledyne Water-Pik, Inc., Ft. Collins, CO).

A test group of 60 patients with occlusal interferences were randomly selected from this general patient population seeking relief from signs and symptoms of TMD varying in duration from 1.5 months to 20 years. While condylar location was not measured before or after jaw registration, it was noted in corrected tomograms before treatment. Definite occlusal interferences of varying degrees were found in all patients when the mandibular condyle was bimanually manipulated into the most superior position within the glenoid fossa by previously described methods [53,54,56]. This test group consisted of 52 females and 8 males ranging in age from 16 to 80 years. They presented with a past history of self-described stressful lifestyle 83% (n=50), previous unsuccessful treatment (protocol not known) of TMD with "splint therapy" 43% (n=26), jaw trauma 40% (n=24) and previous orthodontic treatment 30% (n=18). All patients reporting previous unsuccessful splint therapy did not recall any instances of having their jaws manipulated to a specific position in the course of treatment, other than simply tapping their teeth on occlusal marking paper. No previous splints were available for inspection.
Treatment consisted of two phases:
Phase I was a provisional stabilizing treatment period. Reversible procedures were performed in order to develop a mutually protected occlusion so that all posterior teeth occluded on an orthotic when the mandibular condyles were positioned in the most superior position within the glenoid fossa by means of bimanual manipulation [53-59].
The passive occlusal positioning orthotic was used to either eliminate or minimize signs and symptoms of TMD. This phase also provided for: 1) development of a realistic prognosis, 2) patient education as to any probable limitations of treatment outcome, and 3) determination of whether the patient's expectations could be met. Since reversible procedures were employed, treatment could be comfortably terminated should a patient's expectations have been unreasonable or unattainable.

Therefore, Phase I therapy provided opportunity for development of a knowledgeable and cooperative patient and the emergence of a suitably accurate predictive prognosis for Phase II.

Phase II involved irreversible treatment that provided long-term stabilization of a patient's occlusion and/or articular apparatus as determined by Phase I provisional therapy.
Phase II therapy incorporated five possible dental treatment modalities: 1) repositioning teeth, 2) reshaping teeth (occlusal adjustment), 3) restoration of teeth, 4) arthroscopic and/or orthognathic surgery, and 5) deferring treatment.
While therapy could involve virtually any area of dentistry, it commonly employed restorative dentistry (including occlusal equilibration and odontoplasty), and, to a lesser degree, orthodontics. Surgery was not commonly utilized. Two patients received arthroscopic surgery and one received orthognathic surgery. This report deals essentially with Phase I therapy.
Centric relation was considered to have been obtained when the TMJs could be bimanually loaded, with no tension or tenderness, while the condyles were in their most superior position within the glenoid fossa. Centric relation position was also defined as an "adapted centric posture" when intracapsular dysfunction was asymptomatic and the patient could function in a productive manner [57,58]. Treatment was considered successful when the TMJs were asymptomatic after load testing by means of clenching in maximum intercuspation, with no tension, tenderness or tightness in the joints, and the patient remained free of any functional discomfort, with a stable occlusion, for at least three months.
A wire reinforced heat-polymerized acrylic resin (L. D. Caulk Co., Milford, DE) mandibular orthotic was fabricated for each patient (Fig. 1). All occlusal and incisal surfaces were covered with acrylic resin (Fig. 2), and, when necessary, orthotics were relined with autopolymerizing acrylic resin (TMJ Instrument Co., Inc., Norco, CA) in order to maintain maximum stability. Each patient's orthotic was occlusally equilibrated to their individual centric relation (Fig. 3). In a structurally altered joint, centric relation was considered an "adapted centric posture" or "treatment position" [58,59]. Several reliable methods for achieving centric relation may be employed. This study utilized a commonly described bilateral bimanual mandibular manipulative method [53-59]. Orthotics were adjusted with the patient in both the supine and upright position. Anterior guidance was built into each prosthesis (Fig. 4) so that posterior teeth would be discluded by anterior teeth in protrusive and lateral excursions (Figs. 5A&B). Patients were instructed to wear their orthotic as often as possible.
When occlusal interferences and muscle bracing were present during initial appointments, the patient was instructed to only wear their orthotic until such wear became uncomfortable. By the third or fourth appointment, none of the 60 patients was found to be uncomfortable with their prosthesis. However, because some patients experienced difficulty with speech, they would not wear their orthotic while working. In those cases they were instructed to wear it at night and other times during which they felt stressed.
Patients were evaluated and questioned weekly as to their progress and signs and symptoms of TMD. Each orthotic was equilibrated until all opposing teeth had equal contact with the prosthesis in centric relation [53-59], and cuspid disclusion was present in protrusive and lateral excursions. These adjustments were first accomplished with the patient in a supine position. At the end of each appointment the patient was placed in an upright position and their occlusion rechecked with a different colored occlusal indicator ribbon for any changes from the supine position. Any new interferences were removed.
Weekly evaluation and equilibration periods lasted, on average, approximately ten to twelve weeks, and appointment duration ranged from 1.5 hours at the onset to 10 minutes as Phase I was nearing completion.
In certain cases, it was necessary for a patient to wear an orthotic for as long as a year, or longer, in order to facilitate stabilization of the stomatognathic and articular apparatus.
A patient was considered ready to begin Phase II when they demonstrated no occlusal changes in centric relation occlusion (simultaneous equal contact of opposing teeth with the orthotic) for 3-4 appointments and had no feeling of discomfort.
Patient profile - prior to initiation of Phase I therapy:

Chief complaints of the test group, usually associated with TMD, were: TMJ pain 78% (n=47), headache 77% (n=46), neck pain 71% (n=43), ear pain 57% (n=34), facial pain 45% (n=27), eye pain 25% (n=15), tinnitis 17% (n=10), vertigo 17% (n=10), TMJ clicks & pops 17% (n=10), and difficulty opening 7% (n=4).
Myofascial pain ranging from slight to severe was experienced by all patients. Their pain history and pain perception upon muscle palpation was well distributed within the group: slight 12% (n=7), slight/moderate 23% (n=14), moderate 27% (n=16), moderate/severe 20% (n=12), severe 12% (n=7) and slight/severe 7% (n=4).
Bilateral pain was reported by 82% (n=49) of the patients while unilateral pain was experienced by 18% (n=11).
Occlusal analysis of the test group indicated all 60 patients had various occlusal interferences in their arc of closure when condyles were fully seated in the most superior position within the articular fossa. This caused condylar displacement, as visualized on corrected tomograms during maximum intercuspation.
Balancing side interferences were found in 33% (n=20) of the patients and 25% (n=15) demonstrated working side interferences.
Anterior guidance was evidenced by immediate disclusion of all posterior teeth upon laterotrusive contact of the opposing cuspids and possibly incisors. Anterior guidance was present bilaterally in 40% (n=24) of the patients, absent (but with posterior occlusion) in 37% (n=22), and present unilaterally in 23% (n=14).
Parafunctional dental wear facets were present in 92% (n=55) of the patients and 25% (n=15) had functional facets. The following habits were admitted to: bruxism 5% (n=3), clenching 18% (n=11), bruxism/clenching 50% (n=30) and not aware of bruxing and/or clenching 27% (n=16).
Dental relationships were Class I 43% (n=26), Class II division 1 38% (n=23), Class II division 2 10% (n=6) and Class III 8% (n=5).

Temporomandibular joint dynamics and jaw movement within the test group were: stethoscope TMJ auscultation - clicking 38% (n=23), clicking/popping 53% (n=32), popping 6% (n=3), normal 3% (n=2); Doppler auscultation - crepitation 93% (n=56), normal 7% (n=4); deviation of jaw motion 73% (n=44), no deviation 27% (n=16); joint loading - painful 47% (n=28), no pain 20% (n=12), not recorded 23% (n=20); muscle palpation - tenderness 90% (n=54), no discomfort 10% (n=6); bimanual manipulation into centric relation, adapted centric or treatment position - resistant 97% (n=58), no resistance 3% (n=2).
Doppler auscultation is a helpful adjunctive diagnostic aid that appears to show potential merit [60-63]. Certain joint sounds, as detected by Doppler auscultation, may suggest the possibility of perforation of the articular disc by the condyle, adhesions, anteriorly displaced articular disc and other degenerative joint pathology [64].
Corrected Tomography of the test group's TMJs was take as part of the patient's initial examination, and the following was found: condylar morphology - superior surface flat 35% (n=21), anterior border osteophytic activity or "beaking" 32% (n=19); angle of the eminence - steep 58% (n=35), normal 18% (n=11), shallow 3% (n=2), flattened 7% (n=4), not recorded 13% (n=8); condylar/fossa relationship - anterior 2% (n=1), normal 7% (n=4), superior and distal 58% (n=35), distal 30% (n=18), inferior and distal 3% (n=2).
Patient profile - at completion of Phase I therapy:
Chief complaints of the test group were markedly reduced at the conclusion of Phase I.
Pain reduction, as perceived by the patient, was verbally reported at each appointment. Significant pain reduction was reported by 77% (n=46) of the patients and 18% (n=11) no longer had any chief complaints - 95% success rate. One patient had only a slight reduction in their chief complaint, and this came about only after orthotic anterior guidance was reduced. A pronounced anterior guidance ramp was placed on over half of the orthotics with a flatter plane of occlusion used on the remaining orthotics. Two patients left the practice before completion of Phase I and were placed in the categories of "no change" or "no improvement" below for the purposes of this study.
Stethoscope auscultation of TMJ sounds revealed marked improvement in 83% (n=50) of the patients. No abnormal sounds were detected in 10% (n=6) of the test group - this included 2 patients that started Phase I with normal sounds. No change was detected in 7% (n=5) of patients (included were 2 patients who left the practice before completion of Phase I).
Range of motion was considered to be normal within the following parameters: vertical - anything greater than 40 mm, lateral - anything greater than 8 mm [65]. Mandibular range of motion was improved in 58% (n=35) of the patients and was normal for 38% (n=23) - including the 15 patients that started Phase I with a normal range of motion. No improvement was detected in 3% (n=2) of the patients and reflects the 2 patients who left before completion of Phase I.
While this report deals essentially with reversible Phase I therapy of TMD, it is useful to know how patients were treated in Phase II (irreversible treatment). The question may arise: If Phase I therapy is reversible, why did patients need occlusal modification? The answer is simply: Occlusal interferences were temporarily eliminated by altering an acrylic interim splint. To eliminate these interferences permanently, without an interim splint, irreversible occlusal modifications were necessary. Occlusal equilibration was completed on 70% (n=42) patients, while remaining patients were treated with orthodontics 18% (n=11), orthodontics and orthognathic surgery 5% (n=3), arthroscopic surgery 3% (n=2) and full-mouth reconstruction 2% (n=1). Three patients or 5% elected to not proceed to Phase II because they were uncomfortable (this included 2 patients who left before completion of Phase I).
Clinically acceptable occlusion is possible with either cuspid guidance or group function. However, it has been shown that there is a significant reduction in electromyographic (EMG) activity of elevator muscles with cuspid occlusal guidance as compared to group function occlusion [66-70]. While such a cuspid protected occlusion does not affect muscular coordination patterns during mastication, it does markedly reduce bruxism and clenching [66]. Occlusal interferences have also been found to significantly increase EMG activity and predispose a patient to parafunctional activity such as clenching and/or bruxism [12,59,71-76].
Among other factors, an occlusal splint reduces muscular activity of the stomatognathic mechanism by eliminating premature occlusal contacts [77]. In addition, an acrylic resin occlusal splint allows a practitioner to observe treatment outcomes resulting from occlusal equilibration and alterations between group function and cuspid occlusal guidance. This facilitates development of a reliable prognosis before irreversible changes are pursued.
Centric relation may not be attainable with a structurally altered joint. In those cases, it has been suggested [57,58], a more accurate term might be "adapted centric posture" or "treatment position" where the condyles are seated in the most superior position attainable within the articular fossa.
The resultant 95% success rate in this study was likely due to reduced muscle activity [66-70] through the elimination of premature occlusal contacts, and, when possible, development of cuspid guided occlusion. This success rate was maintained after removal of occlusal splints and completion of Phase II therapy.
It has been claimed that occlusal interference is not a significant etiological factor for TMD because there is a relatively high prevalence of occlusal discrepancies in the general population, which is also free of signs and symptoms of TMD [78]. In contrast, there are individuals in the general population that have a "normal" occlusion and manifest signs and symptoms of TMD [79].
This may be explained, in part, by the fact that teeth do not usually touch except when swallowing or eating. If teeth are in contact at other times, regardless of degree of force, the patient is practicing occlusal parafunction. Dental parafunctional wear may generally be detected by altered occlusal morphology and recent wear facets exhibiting a brilliant surface. Parafunctional habits (clenching and/or bruxism) will increase an already heightened muscle activity caused by the occlusal discrepancies. This response is further modified by both individual biological diversity and individual adaptability to biological and psychological stress within the general population. Perhaps the real question is: When does the sequela of occlusal interferences (muscle hyperactivity and so forth) exceed a patient's physiologic tolerance [79]? Obviously all cases of TMD are not caused by occlusal interferences and/or parafunctional habit patterns, though they may be contributing factors. TMD is apparently a multifactoral condition [48,80-83] involving several etiologies, all of which need not be present and some of which may or may not be variably interactive.
This study was limited solely to a determination of the affect normalizing occlusion with a splint had upon TMD. An occlusal splint may cause other effects, such as a placebo effect, besides its affect upon occlusion. However, 43% of the patients in this study had previous unsuccessful splint therapy, while 95% of the patients experienced significant relief after normalizing occlusion with splint therapy in this study.
A precise cause and effect relationship between occlusal factors and TMD is not as clear as some investigators would like. However, the relationship does appear to exist. It is a realistic and pragmatic consideration in the daily practice of individualized optimum dentistry.
Further prospective, controlled randomized clinical trials involving specific TMD diagnostic groups are needed involving splint therapy and its affects upon EMG, jaw tracking, pain, masticatory efficiency and so forth.


A patient's adaptive capacity is a prime factor in the development of TMD, which is a multifactoral condition. When occlusal interferences of patients having signs and symptoms of TMD were eliminated by means of a mandibular orthotic (which allowed all posterior teeth to contact simultaneously and with equal intensity and pressure) there was a significant reduction or elimination (95%) of pain, as well as TMJ noises (popping and clicking).

While occlusal interference may not be the only factor in TMD, this study suggests that a significant relationship does exist, and it is a practical consideration in the course of treatment planning and delivering optimum dentistry.

The author wishes to thank Dr. Kenneth R. Goljan, Tulsa, Oklahoma, for his assistance in the preparation of this manuscript.

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