Is Occlusion A Primary Cause of TMD?

By Karen McCloy, DDS

Occlusion is the act of the teeth coming together.


A primary cause is a factor that if present will reliably initiate the pathological changes that lead to tmd in a patient that did not previously have tmd

TMD is a state of chronic pain in the tmj and the soft tissues supporting it. Chronic pain implies the presence of neural plasticity, so we are talking about a state of central sensitization involving the trigeminal nerve. There is no rule that says that tmd patients may not have similar changes in other areas of the central nervous system. Saying that someone has chronic pain does not address it's etiology, and someone with a clicking joint does not have tmd unless they have pain.

If you ask me is occlusion an important pain producing factor in patients with tmd the answer is a definite yes. In normal patients, without plastic changes, occclusal dsiharmony may be nociceptive, but that means it is not pain. Once there are neural changes it becomes pain, a form of allodynia where a nonpainful stimulus causes pain, like when you have a headache and touching your skin or brushing your hair hurts, and controlling it is key to calming down that nervous system.

But our treatment has multiple modes of action, besides occlusion.

It has a placebo effect, becasue we believe, and because of that our patients believe they will improve. Plus the decision to seek treatment also changes someones mindset and makes them more in control

Our orthotics are a form of CBT - cognitive behavioral therapy. We insert them and say lips together teeth apart, and the plastic reminds the patient what the correct oral posture is.

Orthotics provide an occlusal effect, because they provide stable and even point occlusion around the arch.

Orthotics have an orthopedic effect because the realign the mandible to the cranial base and cervical structures.

So we are back to Larry's the chicken or the egg. We only see the pain patients, and in them pain is correlated with occlusion, but that is not the same thing as causation. Our 1st study on nonpain patients showed that most of them had some form of occlusal issue, but they did not have pain. So I think something else has to happen.

Establishment of a Temporomandibular Physiological State with Neuromuscular Orthosis Treatment Affects Reduction of TMD Symptoms in 313 Patients

Barry C. Cooper, D.D.S.; Israel Kleinberg, Ph.D., D.D.S., D.Sc.
THE JOURNAL OF CRANIOMANDIBULAR PRACTICE, APRIL 2008, VOL. 26, NO. 2, pp. 104-117.

ABSTRACT:
The objective of this investigation was to test the hypothesis that alteration of the occlusions of patients suffering from temporomandibular disorders (TMD) to one that is neuromuscularly, rather than anatomically based, would result in reduction or resolution of symptoms that characterize the TMD condition. This hypothesis was proven correct in the present study, where 313 patients with TMD symptoms were examined for neuromuscular dysfunction, using several electronic instruments before
and after treatment intervention. Such instrumentation enabled electromyographic (EMG) measurement of the activities of the masticatory muscles during rest and in function, tracking and assessment of various movements of the mandible, and listening for noises made by the TMJ during movement of the mandible. Ultra low frequency and low amplitude, transcutaneous electrical neural stimulation (TENS) of the mandibular division of the trigeminal nerve (V) was used to relax the masticatory muscles and to facilitate location of a physiological rest position for the mandible. TENS also made it possible to select positions of the mandible that were most relaxed above and anterior to the rest position when the mandible was moved in an arc that began at rest position. Once identified, the neuromuscular occlusal position was recorded in the form of a bite registration, which was subsequently used to fabricate a removable mandibular orthotic appliance that could be worn continuously by the patient. Such a device facilitated
retention and stabilization of the mandible in its new-found physiological position, which was confirmed by follow up testing. Three months of full-time appliance usage showed that the new therapeutic positions achieved remained intact and were associated with improved resting and functioning activities of the masticatory muscles. Patients reported overwhelming symptom relief, including reduction of headaches and other pain symptoms. Experts consider relief of symptoms as the gold standard for assessment of effectiveness of TMD treatment. It is evident that this outcome has been achieved in this study and that taking patients from a less to a more physiological state is an effective means for reducing or eliminating TMD symptoms, especially those related to pain, most notably, headaches.

Postural loads during walking after an imbalance of occlusion created with unilateral cotton rolls

Simona Tecco*1, Antonella Polimeni2, Matteo Saccucci3 and Felice Festa1: Tecco et al. BMC Research Notes 2010, 3:141
http://www.biomedcentral.com/1756-0500/3/141.

Abstract
Background: It was showed that stomatognathic functions correlate with alterations in locomotion, that are detectable through the analysis of loading during walking. For example, subjects with symptoms of Temporomandibular disorders (TMDs) showed a significant higher load pressure on the two feet, respect to health subjects, when cotton rolls were inserted. This previous study appeared to suggest that the alteration of postural loads associated to a particular alteration of stomatognathic condition (in this case, the cotton rolls inserted between the two dental arches) is detectable only in TMD's subjects, while it resulted not detectable in health subjects, because in that study, health subjects did not show any significant alteration of postural loads related to the different stomatognathic tested conditions. In other words, in that previous study, in the group of health subjects, no significant difference in postural loads was observed among the different test conditions; while TMD subjects showed a significant higher load pressure on the two feet when cotton rolls were inserted, respect to all the other tested conditions. Thus, the aim of this study was to better investigate these correlations in health subjects without TMD's symptoms, testing other different intra-oral conditions, and to verifywhether an experimentally induced imbalance of occlusion, obtained putting an unilateral cotton roll, could cause an alteration of postural loading on feet during
walking.

Findings:
In a sample of thirty Caucasian adult females (mean age 28.5 ± 4.5), asymptomatic for TMDs, when a cotton roll was positioned on the left or the right sides of dental arches, so causing a lateral shift of the mandible, the percentage of loading and the loading surface of the ipsi-lateral foot, left or right, were found to be significantly lower than in habitual occlusion (p < 0.05). Males were not included because of their different postural attitude respect to females. Further studies in a sample of males will be presented.

Conclusions:
This study showed that in health subjects without TMD's symptoms, an experimentally induced imbalance of the occlusion, obtained through an unilateral cotton roll, is associated to detectable alterations in the distribution of loading on feet surface, during walking.

Systematic Review and Meta-analysis of Randomized Controlled Trials Evaluating Intraoral Orthopedic Appliances for Temporomandibular Disorders

James Fricton, DDS, MS/John O. Look, DDS, PhD/Edward Wright, DDS, MS/Francisco G. P. Alencar, Jr, DDS, MS/Hong Chen, DDS, MS/Maureen Lang, DDS, MS/Wei Ouyang, DDS, PhD/Ana Miriam Velly, DDS, PhD. J OROFAC PAIN 2010;24:237–254.

Aims: To conduct a systematic review with meta-analysis of randomized controlled trials (RCTs) that have assessed the efficacy of intraoral orthopedic appliances to reduce pain in patients with temporomandibular disorders affecting muscle and joint (TMJD) compared to subjects receiving placebo control, no treatment, or other treatments. Methods: A search strategy of MEDLINE, the Cochrane Library, the Cochrane CENTRAL Register, and manual search identified all English language publications of RCTs for intraoral appliance treatment of TMJD pain during the years of January 1966 to March 2006. Two additional studies from 2006 were added during the review process. Selection criteria included RCTs assessing the efficacy of hard and soft stabilization appliances, anterior positioning appliances, anterior bite appliances, and other appliance types for TMJD pain. Pain relief outcome measures were used in the meta-analyses, and the QUORUM criteria for data abstraction were used. A quality analysis of the methods of each RCT was conducted using the CONSORT criteria. The review findings were expressed both as a qualitative review and, where possible, as a mathematical synthesis using meta-analysis of results. Results: A total of 47 publications citing 44 RCTs with 2,218 subjects were included. Ten RCTs were included in two meta-analyses. In the first meta-analysis of seven studies with 385 patients, a hard stabilization appliance was found to improve TMJD pain compared to non-occluding appliance. The overall odds ratio (OR) of 2.46 was statistically significant (P = .001), with a 95% confidence interval of 1.56 to 3.67. In the second meta-analysis of three studies including 216 patients, a hard stabilization appliance was found to improve TMJD pain compared to no-treatment controls. The overall OR of 2.15 was positive but not statistically significant, with a 95% confidence interval of 0.80 to 5.75. The quality (0 to 1) of the studies was moderate, with a mean of 55% of quality criteria being met, suggesting some susceptibility to systematic bias may have existed. Conclusion: Hard stabilization appliances, when adjusted properly, have good evidence of modest efficacy in the treatment of TMJD pain compared to non-occluding appliances and no treatment. Other types of appliances, including soft stabilization appliances, anterior positioning appliances, and anterior bite appliances, have some RCT evidence of efficacy in reducing TMJD pain. However, the potential for adverse events with these appliances is higher and suggests the need for close monitoring in their use.

Is Occlusion A Primary Cause to TMD?

A Multiple Logistic Regression Analysis of the Risk and Relative Odds of Temporomandibular Disorders as a Function of Common Occlusal Features

A.G. Pullinger (Section of Orofacial Pain and Occlusion, UCLA, School of Dentistry, 10833 Le Conte Avenue, Los Angeles, California 90024-1668), D.A. Seligman (Section of Orofacial Pain and Occlusion, UCLA, School of Dentistry, 10833 Le Conte Avenue, Los Angeles, California 90024-1668), J.A. Gornbein (UCLA Department of Biomathematics, Los Angeles, California 90024). Journal of Dental Research.

A multiple logistic regression analysis was used to compute the odds ratios for 11 common occlusal features for asymptomatic controls (n = 147) us. five temporomandibular disorder groups: Disc Displacement with Reduction (n = 81), Disc Displacement without Reduction (n = 48), Osteoarthrosis with Disc Displacement History (n = 75), Primary Osteoarthrosis (n = 85), and Myalgia Only (n = 124). Features that did not contribute included: retruded contact position (RCP) to intercuspal position (ICP) occlusal slides < 2 mm, slide asymmetry, unilateral RCP contacts, deep overbite, minimal overjet, dental midline discrepancies, ≤ 4 missing teeth, and maxillo-mandibular first molar relationship or cross-arch asymmetry. Groupings of a minimum of two to at most five occlusal variables contributed to the TMD patient groups. Significant increases in risk occurred selectively with anterior open bite (p < 0.01), unilateral maxillary lingual crossbite (p < 0.05 to p < 0.01), overjets > 6-7 mm (p < 0.05 to p < 0.01), ≥5-6 missing posterior teeth (p < 0.05 to p < 0.01), and RCP-ICP slides > 2 mm (p < 0.05 to p < 0.01). While the contribution of occlusion to the disease groups was not zero, most of the variation in each disease population was not explained by occlusal parameters. Thus, occlusion cannot be considered the unique or dominant factor in defining TMD populations. Certain features such as anterior open bite in osteoarthrosis patients were considered to be a consequence of rather than etiological factors for the disorder.

By Karen McCloy, DDS
Discussion:

Definitions

Occlusion is the act of the teeth coming together.

A primary cause is a factor that if present will reliably initiate the pathological changes that lead to tmd in a patient that did not previously have tmd.

TMD is a state of chronic pain in the tmj and the soft tissues supporting it. Chronic pain implies the presence of neural plasticity, so we are talking about a state of central sensitization involving the trigeminal nerve. There is no rule that says that tmd patients may not have similar changes in other areas of the central nervous system. Saying that someone has chronic pain does not address it's etiology, and someone with a clicking joint does not have tmd unless they have pain.

If you ask me is occlusion an important pain producing factor in patients with tmd the answer is a definite yes. In normal patients, without plastic changes, occclusal dsiharmony may be nociceptive, but that means it is not pain. Once there are neural changes it becomes pain, a form of allodynia where a nonpainful stimulus causes pain, like when you have a headache and touching your skin or brushing your hair hurts, and controlling it is key to calming down that nervous system.

But our treatment has multiple modes of action, besides occlusion.

It has a placebo effect, becasue we believe, and because of that our patients believe they will improve. Plus the decision to seek treatment also changes someones mindset and makes them more in control.

Our orthotics are a form of CBT.. cognitive behavioral therapy. We inserrt them and say lips together teeth apart, and the plastic reminds the patient what the correct oral posture is.

Orthotics provide an occlusal effect, because they provide stable and even point occlusion around the arch.

Orthotics have an orthopedic effect because the realign the mandible to the cranial base and cervical structures.

So we are back to Larry's the chicken or the egg. We only see the pain patients, and in them pain is correlated with occlusion, but that is not the same thing as causation. Our 1st study on nonpain patients showed that most of them had some form of occlusal issue, but they did not have pain. So I think something else has to happen.

Head Posture and Craniofacial Morphology

Linder-Aronson, S and Woodside, DG: Head Posture and Craniofacial  from Morphology Excess Face Height Malocclusion: Etiolog, Diagnosis and Treatment. Quintessence Publishing Co, Inc., Chicago, IL, pg 24-25.

Section Exerpt:
"The physiologic changes alread described can have a profound effect on facial structure.  For example, Solow and Tallgreen <86> foudn that individuals with large head extensions were characterized by larg anteiror face heights, and also both maxillary and mandibular retrognathism and steep inclination of the mandibular plane to the palatal and anterior caranial base planes.

In addition, a correlation study of predictive relationships <83> observe children for 2-4 years before the age of peak velocity in pubertal skeletal growth.  They found that a large head extension was followed by vertical facial development.  This was characterized by backward displacemetn of the temporomandibular joint, reduced growth in maxillary length, reduced racial prognathism, and less-then-average true foward rotation of the mandible.  On the other hand, head flexion was followed by the opposite facial development.

Electromyography (EMG) has also been used to study this phenomenon.  Hellsing et al<44> determined postural activity in the neck muscles in relatin to extension and flexion of the head in adults.  Both the supra- and infrahyoid muscles responded with increased EMG activity during extension and also with 20 degree flexion of the head.  (figure 1-19 shows thi interrelationship between induced oral respoiration, changed head posture, and the EMG activity of the suprahyoid muscles.  Hellsing and L'Estrange<43> also used transducers to measure the changes in lip pressue on the incisors as individuals changed from mouth to nose breathing.  They found that the upper lip pressure decreased when the patient changed from nose to mouth breathing., but increased during 5-degree extension (fig 1-20).  There was a clear correlation between lip pressure and cranial posture.  Thus, in investigations of the effects of long-term alteration in head posture, compensatory muscle function associated with head extension or flexion may be one of the determinants of craniofacial morphogenesis in growing individuals.  These results support the soft tissue stretching  hypothesis suggested by Solow and Kreiborg<8>  This stretching hypohyothesis is named after one of the links in the porposed chain of events (Fig 1-21).  The coordination of different neck muscles is also important for adequate respiration and head posture.  For example, if the head posture is changed by tilting the head backward from the lower cervicla reiong, the nasopharynx will be narrowed.  However, if hte head is tilted backward from the upper cervical vetebrae, the naso pharynx will be widened (Fig. 1-22). <42,84>

These findings indicate that airway obstruction triggers an increased in head extension via upper cervical vertebrae to compensate for nasopharyngeal obstruction.  This facilitates oral breathing by enlargemetn of the naso- and oropharyngeal airway sapce.  This head extension may create a stretching of the soft itissue envelope of the face and neck and thus initiate malocclusion."

Functional malocclusion that induces posterior condylar displacement

Purisa Cholasueksa, DDSa; Hiroyuki Warita, DDS, PhDb; Kunimichi Soma, DDS, PhDc.: Alterations of the Rat Temporomandibular Joint in FunctionalvPosterior Displacement of the Mandible. Angle Orthod 2004;74:677–683.

Abstract: Functional malocclusion that induces posterior condylar displacement may affect the remodeling
processes of the temporomandibular joint structures. We tested the hypothesis that intermittent posterior
condylar displacement due to functional malocclusion traumatizes condylar cartilage and joint innervated
nerve fibers. Thirty-nine eight-week-old Wistar rats were used. To induce functional posterior
condylar displacement, guiding appliances were attached to maxillary incisors of 24 rats for four, seven,
and 14 days. Fifteen normal rats served as controls. Sections were stained with hematoxylin and eosin or
processed for immunohistochemistry of protein gene product 9.5 and growth-associated protein-43 (GAP-
43). Functional posterior condylar displacement led to a diminution in proliferative cells, reduction in
cartilage width, and re-expression of GAP-43–immunoreactive nerve fibers. These results indicate that
intermittent posterior condylar displacement due to functional malocclusion causes dysfunctional remodeling
of condylar cartilage and nerve injury.

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