Vienna School of Interdisciplinary Dentistry

Education in Occlusion Medicine

Occlusion

Relationship between occlusion and temporomandibular disorders:

 

Implications for the gnathologist

Prof. Dr. Rudolf Slavicek / Vienna

The succession of hominids about 5 or 6 million years ago

 

led to continuous development that culminated in Homo. The first Homo, also known by the basic designation of Homo habilis, appeared about 2 million years ago..

Some reasons for anthropogenesis include posture, speech, brain development,and social behavior. The decisive step in evolution occurred when the new phase of linguistic communication emerged—ie, descriptive language. In a discussion between a Nobel prize winner and one of the greatest philosophers of the twentieth century, namely Konrad Lorenz and Karl Raimund Popper, the following statement emerged: “Brain is language, and language is brain.”
Popper took things farther, claiming that brain is speech, and speech is brain, and that man created himself by descriptive speech.(1,2 ) Indeed, the brain developed with drastic speed, and the evolution culminated in Homo sapiens. The masticatory organ and occlusion are at the center of this link to the development of the brain, because linguistic communication occurred through this new function.

CYBERNETICS AND ORGANISMS

In 1948, Wiener (3) published a provocative scientific book that first described the concept of networking in biology. He stated that cybernetic thinking is the link in the “no man’s land” between the recognized sciences. I describe an organism from the cybernetic point of view as a highly complex and self-contained system that is unified by a common (external and internal) flow of information, which compels all internally dependent subsystems to undergo reactive changes, and is therefore in a state of permanent unstable homeostasis. The permanent reactive adaptation of an organism to maintain homeostasis can be termed “life.” The main purpose of an organism is survival.(4 ) Adaptation and habituation were first elaborated upon by Jean-Baptiste Lamarck in his second thesis, which discussed the genetic outcome if both sexes are habituated. This definition might also be viewed from the perspective of the second main theorem of thermodynamics.
Biologic systems are open systems with a time direction. Here, Prigogine (5) described the so-called dissipative structures in general for open systems and thus also for biologic systems. Processes in biologic systems are “irreversible.” A major aspect of open systems is that all interventions (also therapy) are irreversible. From the perspective of evidence-based medicine, when we separate teeth with occlusal aids and then remove the appliance, a condition of restitutio ad integrum can be achieved. From a scientific point of view, this is absolutely incorrect.
Uexküll (6) initiated a further major modification in biology when he described his new viewpoint about organisms in their environment. If an organism is confronted with a problem in its environment, the organism recognizes the problem, states its importance, reacts, and arrives at a solution to the problem. This reaction is received by the environment as a new reality. The problem is solved both directly and cognitively!
Humans are a suprasystem with a strong relationship between the soma and the psyche. Based upon self-consciousness, the human being creates his or her own individual reality. Because of social structures, education, conventions, inhibited aggression, or the unwillingness to be aggressive, problems are usually not solved directly but, rather, in a delayed manner, or they remain unresolved. We name this psychic behavior suppression. Thus, the psyche becomes a dumping ground for unresolved problems that remain concealed and cognitively inaccessible.
In summary, the masticatory organ of Homo sapiens is an entirely new evolutionary concept with newly networked functional spheres—ie, a “new organ.”(4) In our individual ontogenesis, we must rediscover and relearn the phylogenetic new functions.

ONTOGENESIS OF THE MASTICATORY ORGAN

Before erupting into the oral cavity, the dental crowns are completemorphologic structures, which I define in genetic terms as the 1 structure of the human body that can be altered only by destruction. Due to the sequence of ontogenesis, I prefer to speak in terms of functional periods rather than use the usual classification of growth periods: the postnatal period, breathing and communication, ingestion and digestion, preparation of the spine, changing nutrition, and mastication and swallowing.

Uprighting
Man’s ontogenetic uprighting caused a massive change in the region of the temporal bone. Because of the position of the organ of balance and the archways, the pyramid had to rotate in the opposite direction during uprighting. Counterrotation concerned not only the temporal bone but also all bones of the cranium.(7,8)
During the period of the deciduous dentition, the following typically occur: full development of communicative speech, general learning, social adjustment, psychic stress management through the masticatory organ, and abrasion of the deciduous dentition. Malfunction and malocclusion form during this period. The phase of the mature deciduous dentition is the longest and most effective learning period in life. Therefore, it is a period of extreme psychic narrowing and loading. At this age, bruxing is a normal function to unload the psyche.(9) The resulting abrasion favors the required protrusive advancement of the mandible.

First period of the mixed dentition
With the eruption and coupling of the permanent first molars, the anterior permanent teeth are also exchanged, intercuspal positions are defined, structural limitations are established, functional adaptations (chewing and speech) occur, and the structural adaptation of the temporomandibular joint begins. During this period, the temporomandibular joint adapts just as rapidly. The initial adaptation is functional but is followed by structural adaptation. This means that occlusion dictates adaptation. This ability to adapt functionally as well as structurally persists throughout life, but in a less pronounced manner. As early as this point in time, the morphology of the first molars structurally determines the lateral and retral pattern of the craniomuscular system. The position and rotation of the molars determine the movement pattern of the mandible.(10)
Compensation of sagittal and transverse discrepancies occurs during this time. The first main factor of compensation during ontogenesis is dentoalveolar development. The second main factor to compensate skeletal discrepancies is vertical development. The third main factor, especially in skeletal Class II malrelationships, is articular compensation (temporomandibular joint). Malocclusion in the early mixed dentition must be recognized.

Second functional period of the changing dentition
During the second functional period of the changing dentition, the premolars erupt, there is narrowing of lateral control, retrusive control in the first premolar occurs, and the psychic stress of the beginning of puberty starts. The morphology of the premolars—especially that of the first premolar— is the most important preparatory basis for the final dynamics of lateral, retrusive, and protrusive mandibular movements. From the orthodontic point of view, extractions in this region are functionally critical.(11)    

Functional period of maturation
During the functional period of maturation, canine dominance (12) is established, the craniomuscular system matures into the reference position, second molar intercuspation develops, and there is increasing psychic loading with puberty and increased social integration. In conclusion, during the maturation of the dentition, the position of the mandible is determined 3-dimensionally by the occlusion of the teeth.(13) It is habituated and controlled proprioceptively, while closing the jaw. The joints are secured vertically by the teeth.(14) 

FUNCTIONS OF THE JAW

Mastication
In the phase of bolus formation, mastication should be more of a translatory process. There should be minimum rotation. In modern man, optimum dynamic mastication is achieved when the rows of teeth are as close to each other as possible without functional interferences.(15) Hence, occlusion is undoubtedly the major and dominant factor of the system. Occlusion and articulation determine the functional patterns of mandibular movement.

The term “disclusion” in our modern occlusal concepts is a perversion of the central significance of the masticatory organ: to cut food efficiently. The quality of intercuspation is important for the physiology of chewing. Chewing is concluded by the act of swallowing. Intercuspation should be achieved without interference. The difference between retral contact position and intercuspation in chewing and deglutition is of minor importance. Chewing and swallowing are patterns adapted to the quality of food and controlled proprioceptively during the sequence of mastication. The necessary information is provided by individual tooth contacts during chewing. The front teeth are avoided in mastication. Functional interferences in occlusion can cause avoidance patterns. Avoidance patterns during mastication and swallowing might be a reason for temporomandibular disorders.

Speech
Communication is the main function of the masticatory organ, and pronunciation is predominantly related to the anterior teeth. Other teeth and occlusion
might create avoidance patterns causing TMD.


Bruxing and clenching (the role of teeth in stress management)
The limbic system is the complex system belonging to the archaeocerebellum, located between the brain stem and the neocortex, which is considered to be responsible for emotion and instinctive behavior. Humanization leads to proportional shifts, which cause aggressive behavior.(16) In the evolution of the primate,
a strong shift in balance occurs in the region of the amygdaloid nucleus. The centromedial portions (aggression) are markedly reduced compared with the centrobasolateral (pleasure-oriented) portions.
Kail (17) stated in her dissertation on our bruxing patients in the Department of Prosthetic Dentistry at the Dental University of Vienna, Austria, that any deficiency or disability in direct aggressive behavior could be a reason to use the masticatory organ for reducing stress through bruxism. As a result of her research, she found that the total group of 98 bruxers had significantly reduced general well-being. Furthermore, the personality structures in the study were significantly different from standard random samples of matched groups in regard to general aggressive behavior. In addition, both spontaneous and reactive aggressive behaviors were markedly less than in the control group.
In the lives of the subjects, problem solving frequently occurs either in a delayed manner or by way of compromises or not at all. Such “no solving” of problems is deposited in the garbage dump of the psyche and can be realized at the somatic level through nonpurpose-related emotions.
If chronic pressers and grinders use their masticatory organ as a psychic stress valve, then grinding and pressing might be assigned to the normal functions of the masticatory organ.18 For these people, decrying parafunction in the treatment of the masticatory organ would signify an additional restriction. What is the role of occlusion in coping with stress? This discussion must be conducted unemotionally on the basis of scientific findings and conclusions. Grinding and clenching
are expressions of psychic stress assimilation and are controlled by the neuromuscular system and occlusion.(19-33)

Therapy of occlusion: Goals and concepts
Interventions in the structure of occlusion are irreversible. This is based on the widely accepted axioms of the natural sciences. All assertions of reversibility are scientifically unfounded. Therapeutic interventions must have a causal reason. The purpose should be defined, and the aim should concur with the purpose. This is applicable to restorative and prosthetic interventions in equal measure as it is to orthodontic and maxillofacial surgical corrections. After completion of the
treatment, the result should be biologically stable.(34) So-called retentions might be indicated in the phase of stabilization, but a general retention of the occlusal outcome is incorrect. Defensive assertions to the effect that therapeutic interventions can have no negative consequences are absurd.
“Gnathology” is defined as “the science that treats the biology of the masticatory mechanism as a whole: morphology, anatomy, histology, physiology, and therapeutics of the jaws or masticatory system and the teeth as they relate to the health of the whole body, including applicable diagnostic, therapeutic, and rehabilitation procedures. The conceptual dogmatism of the term gnathology in earlier days was a problem or cause that split occlusionists from nonocclusionists. But dogmatic wars are counterproductive. Independent from skeletal individuality, human teeth are nearly morphologically the same. Canines and anterior teeth are controlling and/or guiding; posterior teeth support and disclude. The modern gnathologic concept is clearly proven and can be recommended. Any other concept in orthodontics must be defined but must fit with the natural morphology of teeth and must be verified by scientific data.(35,36)

CONCLUSIONS

The teeth occlude and determine the motion pattern of the mandible. Furthermore, motion patterns occur in the neuromuscular system and are regulated proprioceptively. The signals of proprioception occur in the teeth, the periodontal ligament, the temporomandibular joints, and the muscles themselves. Intact teeth provide the most rapid information to the brain in monosynaptic fashion. The functions of the masticatory organ are entirely different and closely networked with the somatic and psychic functions of the brain. Of course, there are adaptability and a compensatory capacity. However, the masticatory organ and the psyche are strongly linked.

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