The occlusal theory further complicated

A Revised View of the Dynamics, Physiology, and Treatment of Occlusion: A New Paradigm

A new perspective is proposed regarding the functional dynamics of occlusion, the masticatory muscles, and mandibular placement. Each is analyzed on the basis of a new criterion: force. Stomatognathic function is represented as an ongoing equilibrium maintained between the three-dimensional set of individual occlusal forces and the three-dimensional set of bilateral muscle forces. Mandibular placement is of prime importance, mediating as it does between the two. The conclusion is drawn that occlusion and the muscles can correlate optimally with each other only when the mandible occupies its neuromuscular position (NMP), herein defined as that placement where muscle accommodation is at its absolute minimum. The conclusion is that only the muscles themselves are capable of establishing the NMP and that customary conventional technology is inadequate. A new technology, hydrostatics, is needed to create the special (not existing naturally) occlusal conditions essential to optimally integrating occlusion, mandibular placement, and muscles. Preliminary EMG data is offered in support of this conclusion.

Occlusal Characteristics in Subjects with Facial Pain Compared to a Pain-Free Control Group

Facial pain has been considered a common symptom of temporomandibular disorders (TMD) with a multifactorial etiology. There is controversy regarding the role of occlusion in the background of facial pain and TMD. The aim of the study was to compare the occlusal relationships with two definite measurements in subjects with and without facial pain, in a population-based sample of young adults. The study is part of the Northern Finland 1966 Birth Cohort Project. A subsample of the cohort was formed based on a questionnaire and consisted of 104 subjects, including 52 subjects with facial pain and 52 non-pain controls. Analyses of the dental occlusion of the subjects were performed in gypsum casts by following two methods: 1. the Peer assessment rating (PAR), according to Richmond, et al. (Method 1), and 2. the bilateral canine relationship and the dental midline measurement by the method presented by Pirttiniemi, et al. (Method 2). Method 2 showed higher sensitivity in detecting sagittal occlusal discrepancies than Method 1. Assessment of the intermaxillary relationships in terms of the canine relation showed the lower canine to be more mesially located in the facial pain group, compared to the controls, measured by Method 2. It can be concluded that differences in occlusal sagittal relationships, especially mesial canine relation, seem to correlate with facial pain symptoms at population level.

Reciprocal influence of masticatory apparatus, craniofacial structure and whole body homeostasis

There are evidences that the evolution into Homo erectus was partially induced by masticatory muscular dystrophy caused by a gene mutation, which in turn increased brain capacity and led to bipedalism. It is generally accepted that the morphology and function of mammalian skull are partially controlled by epigenetic mechanisms. Archeologic evidences support that the masticatory apparatus have influenced the mechanical stress distribution in hominin skull, and consequently changed craniofacial morphology and function. Even after evolution into H. erectus, alterations in food properties by civilization and cultural preferences have caused modification of human masticatory pattern and accordingly craniofacial structure. Since there are evidences that prehuman and human masticatory apparatus has been influenced the craniofacial and whole body morphology and function, this apparatus in turn might influence whole body homeostasis. Plausible reciprocal influencing mechanisms of the masticatory apparatus on the whole body homeostasis might be (1) direct mechanical influence on the craniofacial structure, (2) distortion of cerebrospinal fluid circulation, and/or (3) several neural/humoral routes. Based on these backgrounds, the hypothesis of the present study is that the morphology and function of masticatory apparatus influence the whole body homeostasis and these interactions are reciprocal. Therefore, human masticatory apparatus, at the present time, should be kept in its physiological status to maintain the whole body homeostasis. We recommend basic and clinical approaches to confirm this hypothesis.

Incidence and prevalence of temporomandibular joint pain and dysfunction. A one-year prospective study of university students

OBJECTIVE

The aims of this study were to investigate the incidence and recovery of temporomandibular joint (TMJ) pain and dysfunction during a 1-year period, and to examine factors associated with TMJ signs and symptoms.

MATERIAL AND METHODS

The study population comprised 371 dental students examined at the start of education, out of which 308 were re-examined after 1 year. Case histories were collected with the aid of a questionnaire. The clinical examination involved TMJ mobility, TMJ pain, TMJ sounds, morphological and functional dental occlusion.

RESULTS

The 1-year incidence of TMJ signs and/or symptoms was 12%, with no statistically significant difference between men and women. Reported TMJ sounds (10%) and clinically registered TMJ pain (8%) reached the highest incidence rates. Approximately a quarter of those who had TMJ signs and/or symptoms at baseline had recovered at follow-up. Subjects with a non-symptomatic TMJ were significantly more often found among men and among those with bilateral contacts in centric relation, a normal transverse inter-maxillary relationship, and a stabile mandibular position in centric occlusion.

CONCLUSION

The 1-year incidence of TMJ pain and/or dysfunction was high among 1st-year university students. The persistence of signs and symptoms during the observation period was related to gender, while incidence and disappearance of symptoms were not. Dental occlusion was not rejected as a possible concurrent factor in relation to TMJ pain and/or dysfunction among university students.

Subjective reactions to intervention with artificial interferences in subjects with and without a history of temporomandibular disorders

In a previous double-blind randomized controlled study, subjects with a history of temporomandibular disorder (TMD) reacted to artificial interference with more signs of TMD than did subjects with no TMD history. In the present study, we analysed the subjective reactions of these individuals on several symptom scales. Every day during the 2-week follow-up period, the subjects rated the intensity of their symptoms on 9 VAS scales (occlusal discomfort, chewing difficulties, tender teeth, fatigue in the jaws, headache, facial pain, opening difficulty, bruxism, ear symptoms). Subjects with a history of TMD and true interferences reported stronger symptoms than subjects with no TMD history and placebo interferences. The most prominent symptoms were occlusal discomfort and chewing difficulties. The difference in outcome between the groups with and without a TMD history suggests that there are individual differences in vulnerability to occlusal interferences. It is likely that the etiological role of occlusal interferences in TMD has not been correctly addressed in previous studies on artificial interferences.

Effect of artificial occlusal interferences depends on previous experience of temporomandibular disorders

Studies on artificial interferences in subjects with no temporomandibular (TMD) history have shown adaptation to the interference within a fairly short period of time. The role of occlusal factors in the etiology of TMD has therefore been questioned. The results might have been different, however, if subjects with a prior TMD history had been included in the study groups. To test this assumption in a randomized double-blind clinical set-up, we included healthy women without (n = 26) as well as with (n = 21) an earlier TMD history. Both groups were randomly divided into true and placebo interference groups. Artificial interferences were introduced in the true interference groups and simulated in the placebo groups. The subjects were followed for 2 weeks, after which the interferences were removed. The subjects without a TMD history showed fairly good adaptation to the interferences, but the subjects with a TMD history and true interferences showed a significant increase in clinical signs compared to the other groups. We suggest that the etiological role of occlusal interferences in TMD may not have been correctly addressed in previous studies with artificial interferences and allow no conclusions as regards TMD etiology.

Temporomandibular disorders, occlusion, and neck pain in subjects with facial pain: a case-control study

The etiology of facial pain is multifactorial. Based on the results of a questionnaire included in the study of the 1966 Northern Finland Birth Cohort, performed in 1997-98, we found an association of facial pain with subjective symptoms of temporomandibular disorders (TMD), neck pain and with occlusal factors reported by 5,696 subjects. The aim of the present study was to examine these associations clinically. In the year 2000, a new inquiry was sent to the following subjects living in Oulu: 1. all subjects who had reported facial pain in the former questionnaire (n=162) (case group); and 2. to a randomly selected group of nonpain controls (n=200), group matched for gender. Those who reported willingness to participate were invited to a clinical examination. Finally, the total number of subjects was 104, including 52 (10 men, 42 women) cases and 52 (10 men, 42 women) controls. Anamnestic data were collected, and clinical stomatognathic and musculoskeletal examinations were performed, both the clinicians and the subjects being unaware of the case-control status. Anamnestically, stress was the most often reported provoking factor for facial pain. Facial pain associated significantly with reported TMD symptoms and allergies. Based on clinical findings, most of the cases were classified in the myogenous subgroup of TMD. The risk for facial pain was six-fold in subjects with clinically assessed TMD, defined as moderate (DiII) or severe (DiIII) by Helkimo's clinical dysfunction index, almost six-fold in subjects with protrusion interferences and approximately three-fold in subjects with clinically assessed tenderness of distinct fibromyalgia (FM) points in the neck. According to the adjusted logistic regression analyses, TMD had the strongest influence on facial pain, followed by protrusion interferences, anamnestically reported allergies and "other headaches". The present study shows that as well as being connected with TMD, facial pain is associated with pain and muscle tenderness in the neck area.