The Impact of the Stomatognathic System on the Development of Human Beings

PRACTICE MINIREVIEW 171

The impact of the stomatognathic system on the development of human beings

Question tion. Food was devoured without ism is linked to the brain, or CNS, in Which of the versatile complex func- chewing. A large part of the energy the most complex and versatile way. tions of the stomatognathic system contained in food was therefore The brain stem is largely in charge of play a key role in human devel- needed in processing the food in the neuronal control of “simple” func- opment? intestinal tract. Multidimensional tions such as chewing, defending or chewing, grinding of the food and threatening others. Among others, a Background predigesting through the addition of central area referred to as a mastica- The stomatognathic system and its saliva’s enzymes occurred more and tory center is located here. It controls comprehensiveness and meaning for more in the course of evolution. the chewing process after initiation the entire organism is underesti- Chewing movements became in- by associated centers in the cerebral mated even by dentists. We usually creasingly complex and eventually cortex mostly autonomously, but al- only speak of the chewing organ and led to the development of a new ways fed back by sensible, sensory this concept alone seems to reduce mandibular joint, which is still centers (that process peripheral in- our operating field to restoring the found in mammals (mammalia) formation). function of “chewing”. However, the today. The original hinge joint The basic functions of the stoma- stomatognathic system has many evolved to become the ossicles of the tognathic system mentioned above other functions and plays a key role middle ear (ossicular chain). The os - are complemented by the formation in the evolution from hominoids to seous mandibular corpus is a meso- of sounds in mammals (mammalia) homo sapiens as opposed to other derm derivative that has a growth and birds (aves) [2]. The main focus organ systems. It consists of numer- center specifically in the area of the of the development of a sound is un- ous structures that form a complex ascending jawbone that links the doubtedly in the larynx, where its cypernetic regulatory circuit (Fig. 1a, condyle and caput mandibulae to specific structure makes a modu- Fig. 1b), which themselves show os - the structures of the neurocranium. lation of sounds possible. But also the seous, chondral, ligamentary, muscu- It is characteristic for our mandibular shape of the oral cavity plays a key lar, fascial, organic and neuronal con- jaw that osseous and cartilaginous role in sound formation and func- nection with other systems. structures such as condyle, condylar tions as a resonance space. The de- The primary functions of the sto- cartilage, articular disk and articular sign and modification of the oral cav- matognathic system were food in- capsule evolve in parallel and cluster ity with tongue, teeth, cheek and lip take, defense and the presentation of together. This evolutionary process muscles, muscles of the soft palate threatening gestures in order to es- required perfect coordination of all and the mucosa all contribute signifi- tablish a social ranking order. Pres- growth processes considering the cantly to the specific formation of ently, we find these simple functions spatial limitation of the fast evolving sounds. Only in humans, the in various phylogenetic inferior ani- structures of the neurocranium and formation of sounds has evolved to mal species. From the ectoderm, viscerocranium as well as the neck. It the level of language. According to fangs evolved from what used to may explain the difficulty in diag- Popper [7] we differentiate the fol- originally be skin scales to capture nosis of dysfunction of the stoma- lowing stages of speech/articulation: and fixate food [8]. A simple hinge tognathic system. Due to its many – Stage 1: Expressive or sympto- joint with a one-dimensional flap individual functions, the stomato - matic function: The living being motion was sufficient for this func- gnathic system in the human organ- expresses inner emotional states

Translation: Yasmin Schmidt-Park Citation: Behr M, Fanghänel J: The impact of the stomatognathic system on the development of human beings. Dtsch Zahnärztl Z Int 2019; 1: 171–174 DOI.org/10.3238/dzz-int.2019.0171–0174

such as fear or well-being, for example the purr of a cat – Stage 2: Signal or signal-trig- gered function: For example, warning cries of birds that alert their fellow species to warn of danger and to trigger flight be- havior. – Stage 3: Descriptive function: items or conditions, such as the current or future weather, can be described to other living beings using articulation and can therefore be communicated – Stage 4: Argumentative function: Exchange of abstract processes that can occur in different time levels (past, present, future) and spaces. Critical evaluations, Figure 1a Cybernetic regulatory circuit and neuromuscular control of masticatory plans and decision making on function. occurrences in the environment can be articulated. Stage 3 and particularly stage 4 are only present in humans. Even chim- panzees (pan), our closest relatives are only capable of creating stage 1 and 2 sounds. The attitudes differ on how far the primate morphology of the larynx does not allow speech. Unlike Lie- bermann [6], Tobias [10] shares the view that fundamentally, the higher primates’ morphological differences in the upper airways are not an explanation for their inadequate speech functions. In a study in the USA a chimpanzee baby and a human baby were raised in the same family [4]. The surroundings and support were practically identical for both infants. While the human baby practiced its speech function through continuous babble Figure 1b Cybernetic regulatory circuit and neuromuscular control of speech function. and sound formation, the chimpanzee baby was mostly mute. It never learned our stage-3-speech function, to name objects in the room, and es- we differentiate a dominant and a metic and computerized functions. pecially not stage-4-speech function, non-dominant brain half [2, 5]. The The right cerebral hemisphere is which the human baby learned in the dominant left cerebral hemisphere linked to consciousness (however, course of its development. has a connection to our self-con- not self-consciousness). It processes Eccles sees an explanation of this sciousness as an independent person. non-verbal information, tactile geo- situation in brain development as It analyzes verbal, linguistic descrip- metric information e.g. of the room well. Brain size does not solely play a tions, conceptual similarities, ana- and analyzes image and space pat- key role. In humans – approximately lyzes time and is capable of arith- terns, visual similarities and can carry 30.000 years ago – the development metic and computerized functions. out syntheses on this time period. of both brain halves took a new di- (Fig. 2). The dominant left cerebral We owe the ability of speech of rection into cerebral hemispheres. hemisphere has a connection to our stage 3 and 4 cross-modal links of dif- The brain halves, which would have self-consciousness as an independent ferent sensory centers of both hemi- practically fulfilled inversely identical person. It analyzes verbal, linguistic spheres as well as specially developed functions, specialized on the contrary descriptions, conceptual similarities, areas of the left hemisphere. These are to other mammals. In homo sapiens, analyzes time and is capable of arith- the anterior speech cortex (Broca’s

Figure 2 Cortical language fields of the left dominant cerebral hemisphere. The left cerebral hemisphere is depicted laterally (from below) and medially (from above). Re-drawing after [2].

speech area), the upper speech cortex opment encouraged it and made it and especially the posterior speech possible to develop advantages of al- cortex (Wernicke’s speech area) (Fig. truistic action and the value of cul- 2). In the animal kingdom tactile, vi - tural effort (Fig. 4). The potential of sual or auditory sensory stimuli are al- human evolution exponentiated ex- ways connected with a “limbic stimu- plosively. It is no longer dependent on lus” [2], and therefore determine the random “improvements” through living beings action. Human beings mutations in genetic material, and is can also associate not-limbic sensory no longer reliant on other living stimuli, become conscious of them beings [2]. and can orient their actions accord- The development of these ingly. Using language, the division be- unique, new cross-modal links are tween different senses can be over- readable in the human brain’s to - come. It helps us to merge different pography (Fig. 2). We find the ante - sensory modalities into one unit, rec- rior language center directly before ognition and experience. Teuber [9] zones that are responsible for con- expressed this fact in the following trolling relevant muscles. In the case way: “Language frees us to a great ex- of motoric aphasia the cause of the tent of the tyranny of the senses.” malfunction is in the use of the Through language, human beings muscles used for articulation, rather have succeeded to formulate, evalu- than their paralysis. The posterior ate, and share sensory experiences language center of the left cerebral with others, or rather, to profit from hemisphere is crucial for the initi- the wealth of experience of other ation, execution and understanding people. Through language, the bene- of language. If this structure is dis- fits of the upright walk (verticali- rupted, neither written nor spoken sation) and an subsequent modifica- language can be understood. When tion of the skull base could fully un- looked at in a side by side compari- fold (Fig. 3) [3], which leaves the son, a hypertrophy of the structure

(Fig. 3: By courtesy of Leopoldina) hands of manual tasks free to develop referred to as planum temporale of their full potential. The results of the posterior language center can be Figure 3A–C The changing of sphenoid- manual skills were “discussed” and seen in the area of the superior tem- clivus angles (basicranial angulation) of more importantly passed on, so that a poral gyrus in the left hemisphere. the skull of a dog (canis familiaris) (A), an ape (pan) (B) and a human (homo sa- further growing wealth of experience Topographic and functional rela- piens) (C) in the course of evolution [3]. could be formed. Language devel- tionships can be demonstrated in the

peripheral nervous system. The cra - nial nerves V (trigeminal nerve), VII (facial nerve), IX (glossopharyngeal nerve), X (vagal nerve) and XII (hy- poglossal nerve) supply all structures of the masticatory apparatus. Cranial nerves IX (glossopharyngeal nerve) and X (vagal nerve) supply the speech apparatus structures within and outside of the larynx. Thus, cra - nial nerves as well as masticatory and speech apparatus are demanded simul taneously in various diseases J. Fanghänel) (Fig. 1, 2 and 4: M. Behr, (common cold, childhood illnesses). Figure 4 Left: System of positive reinforcement between 3 biological and a cultural Lastly, the limbic system of the element. Right: Modified feedback system across generations considering language, cerebrum is mentioned. This is a a biological determined skill to pass on cultural views and practices of survival value to further generations. Language possibly plays a key role in the autocatalytic system. non-homogenous structure that con- Re-drawing after [2]. sists of the cingulate gyrus, hippo - campus formation, as well as the amygdalaoid corpus. This system is responsible for emotions and mem- (eds.): Speaking of apes. Plenum Press, ory. It is functionally linked to the implants in the jaw bone interacts New York 1980, 287–330 chewing and speech apparatus: For with an extremely sensitive and 5. Levy-Agresti J, Sperry RW: Differential example, memorable emotions are highly complex biocybernetic regula- perceptual capacities in major and minor created while eating meals that taste tory circuit (Fig. 1a, Fig. 1b). We are hemispheres. Proc Natl Acad Sci 1968; delicious or terrible. We then speak not just practicing in a chewing 61: 1151 emotionally about our sensation. The organ, it is an essential part of our 6. Liebermann P: On the origin of stomatognathic system and speech body that makes us who we are: hu- speech. Macmillian, New York 1985 apparatus are equally involved. mans. 7. Popper KR, Eccles JC: Das Ich und sein Gehirn. Piper, München, Zürich Statement 1982 References For the stomatognathic system, the 8. Schumacher GH, Schmidt H, Richter widespread neural crosslinking imply 1. Behr M, Fanghänel J: Kraniomandi - W: Anatomie und Biochemie der Zähne. buläre Dysfunktionen. Antworten auf that its muscles serve multiple func- Volk und Gesundheit, Berlin 1982, 33–51 Fragen aus der Praxis. Thieme, Stuttgart, tions [1]. While the control pulses for New York 2019 9. Teuber HL: Lacunae and research ap- chewing are derived mainly from the proaches to them. In: Millikan CH, Darley 2. Eccles JC: Die Evolution des Gehirns – older/more ancient parts of the hind- FL (eds.): Brain mechanisms underlying Die Erschaffung des Selbst. Piper, speech and language. Grune & Stratton, brain (pons, cerebellum), midbrain München, Zürich 1994 New York, London 1976, 204–216 and basal ganglia, the neural im- 3. Fanghänel J, Schumacher GH: Schä- 10. Tobias PV: Recent advances in the pulses for speech formation are de- delwachstum und Statik. Nova acta evolution of hominids with special refer - rived mainly from the more juvenile Leopoldina NF 1986; 262: 585–595 ence to brain and speech. In: Chagas C: speech areas of the left cerebral hemi- 4. Gardner RA, Gardner BT: Compara - Recent advances in the evolution of pri- sphere. tive psychology and language acquisi - mates. Pontificiae academiae scientarum. In addition to the afore men- tion. In: Sebeok TA, Umiker-Seboek DJ Scripta varia, Vatican City 1983, 85–140 tioned spatial complexity in the set up of the stomatognathic system dur- ing the growth phase into skull structures, another complexity in neu - rological „wiring“ of the stomato - gnathic system exists (Fig. 1a, Fig. 1b), which contains impulses of different neurological centers with various tasks. Furthermore, this complex- (Photo: UKR) ity explains the difficulty to diagnose (Photo: UKR) and understand problems in the stomatognathic system’s function. PROF. DR. MICHAEL BEHR PROF. DR. JOCHEN FANGHÄNEL University of Regensburg As dentists, we should be aware of University of Regensburg Faculty of Medicine Faculty of Medicine this truth. For example, someone Franz-Josef-Strauss-Allee 11 Franz-Josef-Strauss-Allee 11 who changes the position of occlu- 93053 Regensburg 93053 Regensburg sion, moves teeth in the jaw or places [email protected] [email protected]