Chewing gum. The final milliseconds.

 

Imagine” – John Lennon

 

Imagine a perfect occlusion

A mandible of match below

Nothing to grin or gag for

Above us only sky

 

Imagine, no bite interferences,

it’s easy if you try.

There’s no stop in chewing

The mandible just glides

 

Imagine all the people

Chewing gum at ease

Yo hoo…,

You may say I’m a dreamer,

but I’m not the only one.

 

Examining my patient’s lateral excursions with the Tscan helps me to identify posterior tooth contacts that interfere with the smooth mediotrusive glide of the mandible in their chewing movements. I have realized that the final mediotrusive jaw-movement in the gum-chewing cycle, for many of us, consists of many temporally alternating bursts and quiet periods of directionally opposing muscles. The fewer the number of interfering back-tooth-contacts there are, the easier the chewing process is.

Watching the occlusal contact forces developing to different sets of teeth in the process of laterotrusion, I have learned to understand how the antagonism of muscles of conflicting orientation slows down the velocity of the mediotrusive and laterotrusive movements of the mandible. It is the number of these back-tooth interferences that determines why some individuals are more confident with their gum chewing, for others it is hell.

Mutual exclusion of the activity of antagonistic muscles must be universal to jaw-closures.

Imagine an ideal world, where, during the mediotrusive glide of the mandible, there would not be any interfering back tooth contacts. There would just be the steady flow of tactile sensory information coming from the working side canine teeth and the anterior region. The ideal medial pterygoid would be active, unhindered and triumphant, bringing the mandible home swiftly to the maximum intercuspal position (MIP), whilst the other, more vertically oriented muscles of jaw-closing would ideally be at rest.

At the absolute ideal instant, as the ideal mandible would hit its ideal home – at the MIP, the amount of occluding back-tooth contacts would suddenly increase. The sensory information from the back-teeth from the left and right side of the dentition would increase dramatically. There would be an overflow of sensory information coming from the back teeth. That’s a lot of orders for the motor ganglia to once again start the left and right masseter and temporalis muscles going. The tiny amount of a different kind of sensory information from the anterior teeth would be overwhelmed at the instant. Now it would be the time for the medial pterygoid to be silent.

It does not matter, whether the mandible is homing to the MIP from a lateral excursion. The same things happen in an habitual, non-manipulated, vertical down-up jaw-closing. The interesting thing is the beautifully organized interplay with the muscles. The different orientation of muscles necessitates that their activity cannot be happening at the same time for all of them. It is my logical assumption that the activity of the medial pterygoid must emanate from the tactile sensory signals of the anterior dentition.

My narrative of the final milliseconds of the chewing cycle is based on what I can see happen in a Tscan recording. Anyone who has got a Tscan can easily check out what happens when the mandible hits the MIP in habitual closing movement. The computer software gives a mark “A” for the time-point of the first point of occlusion contact. In an unassisted closure of the mandible the pull of the muscles is the only determinant for the movement of the mandible. The sensors of the muscle spindles may be involved to guide the movement but as long as the upper and lower jaw teeth do not touch each other there is no sensory information coming from the teeth. Only after the time-point “A” a flow of sensory information starts emanating from the teeth.

For almost any person with an undisturbed, vaguely “normal” bite, it is a tooth-pair from the anterior area that hits first. The first occluding pair of contact very seldom appears on the back-teeth, except for patients with gross back-tooth prematurities. For subjects with more or less “normal” curve of Spee, the normal course of events is that the anterior teeth hit first. The anterior teeth, sort of, prepare the ground, after which, the more forcible back-tooth contacts are encouraged to take effect. This is what I think is the normal conduct of a natural occlusion in vivo.

During these initial milliseconds, after the time-point “A”, there may be some pairs of teeth that occlude more forcibly relative to other pairs of teeth. Without a Tscan it is impossible to see where these excessive points of contact force happen. Occlusion foil ink marks help to identify the occlusion points of contacts that appear on the Tscan software. The appearance of the ink spots, however, correlates poorly with the force.

In the anterior area often, but not always, there appears to be tiny lines on the palatal aspect of the maxillary incisors and canines. These lines are due to the initial forced gliding of the mandible into retro-gnathic, or worse, lateral direction. These line-drawings are often less than a few decimals of a millimeter, nevertheless these interferences profoundly effect a forced deflection of the as yet occluding dentition out of the position that otherwise would be preferred by the muscles. The Tscan software detects and displays such force outliers. For a clinician the force outliers on the anterior teeth are a powerful sign of trouble in jaw closing. Rapidly increasing growth of force on the anterior dentition makes the control system of jaw closure alarmed in about as short a time as it takes for a nerve impulse from the periodontium of an anterior teeth to be transported, via myelinated nerve fibers, to the ganglia of the brain stem. The sensory signal from the anterior teeth sends a very rapid warning signal, that kills the vigorous activity of the temporalis and masseter muscles. As long as there are prematurities (i.e. force outliers) of the anterior teeth, considerably long time can occur between the initial tooth contact (point ”A”) until the moment, when all the tooth contacts are finally secured to lock each other at the MIP. A slight adjustment of a such prematurity in the anterior area immediately makes a therapeutic intervention. The patients normally notice the change themselves. Tapping the teeth together, they say, goes in a more relaxed way. In contrast, leveling off any prematurities of the back teeth would usually go unnoticed by patients. It is my experience, and I would like to stress that it is quite mandatory not to touch any of the high force contact points of the premolar and molar area in the initial phase of adjustment of occlusion.

The anterior teeth, that become subjected to rapidly growing relative force, as compared to their neighbouring teeth in habitual jaw-closing, can also be identified by holding the examiners fingertips on the facial side of the anterior teeth while the patient taps his/her teeth together. The fremitus is coincident with the force pillars that appear on the computer screen in the Tscan 3-D graph. Usually, to attain force equilibrium within the six anterior teeth pairs only requires a minimum amount of adjusting. It is my way of removing tooth/filling -material with a diamond bur to start from the most incisal end of the tiny ink lines of excessive force on the palatal of the front teeth. The ink foil markings should be repeated until the front teeth contacts should appear as dots, not lines. Consequently, no more fremitus should be felt by the fingertips of the examiner. With a Tscan, the anterior tooth contacts should be light, evenly distributed and barely discernible with the set level of voltage of the sensor. Most of the total force becomes to rest on the back teeth. Milliseconds later, another workshift-change of the muscles occurs again. A powerful clench can be observed on the total force curve on the time vs. force graph. The mandible is securely at home and the temporalis and masseter muscles are triumphant again.

To conclude, the description above ends my narrative of what I imagine takes place during the final milliseconds of the chewing cycle. This article also offers an outline of a therapeutic clinical procedure that should precede any other interventions to change the occlusion of our patients.

 

 

Chewing gum is not good for you?

Those dentists, who are oriented to treat patients suffering from bite-related problems, don’t like chewing gum. Strange, isn’t it?

One would think that a little exercise for the jaw muscles can’t be bad. Shoulder-pain-doctors, back-pain-doctors and all the rest of professionals who treat patients with any problems related to the muscle and joint function, always applause physical exercise. The common, and empirical, knowledge of almost any doctor in the jaw-closing-business is, however, that chewing gum aggravates their patient’s joint and muscle problems. What’s wrong with chewing gum? What can be unnatural in chewing? Isn’t the process of chewing the hallmark of human civilization? Convivial jaw movement in a dinner table society is a powerful social gesture. Throughout the existence of human race, the ability to effortlessly chew one’s food – as unhesitant as the rest of the dining company – has been positively determining the social status and the acceptance of an individual as a member of a social group. The inability to show the gesture of mandible movements, to chew one’s food as the others do, provokes caution in a social group. The amicable social cohesion of The Beefeaters dinner party becomes strained as soon as a member of the Beefeater club suddenly, after the soup, when the roast has been brought into the table, becomes aware of the hesitant jaw movements of a fellow member sitting on the opposite side of the dinner table.

“How come, is there something wrong with the steak?” inquires the alarmed table-mate. He had just recently recognized the same uneasy kind of chewing pattern with her daughter at his own family dinner table. To his dismay, he had learned his daughter having become succumbed to the influence of a television documentary dealing with the ethics of animal farming and animal rights.

“No worries”, replied the uneasily chewing Beefeater. The ethical aspects of meat-eating had never been his concern, the trouble was the filling his dentist had made just in the afternoon before the dinner. The filling was high and prevented him from chewing normally.

In my previous blog article: “Chewing gum. Details of the process and a remark on its social implications” I reasoned that after the food bolus has become crushed between the molar and premolar teeth, the bits and morsels are supposed to be milled by a smooth mediotrusive roll of the mandible from the working side lateral excursive position to the midline. The mediotrusive move of the mandible cannot happen, unless there is a constant sensory signal from the anterior teeth, that switches on the activity of the median pterygoid muscle, that brings the mandible medially towards the maximum intercuspal position of the dentition of the upper and lower jaws. The path of return of the mandible from lateral excursion to the midline must be unobstructed by disturbances from the back teeth. A slightest touch in the back would cause a burst in temporal and masseter muscles, and the activity of their antagonist, the medial pterygoid muscle would be stalled. This wouldn’t make a smooth mediotrusive movement, but a jagged zig-zag locomotion, where the temporal alternation of either up or medially  orientated muscle groups, depending on the amount of posterior contact interferences, would be negotiating the path of return to the midline of the mandible. Alaleuan liikesuunnat sulkemisessa osissa

The lateral excursion test is an essential part of any proper dental examination. We want to see whether our patients’ jaw glides effortlessly to the lateral. In the lateral excursion test we examine, the other way around, the same path of gliding that happens when our patient does the end phase of his/her chewing cycle. In the following illustration, I have drawn an orange arch to give an idea where the dental arch of the upper jaw lies. Pink arch gives an idea of direction of the movement of the mandible. The extent of the jaw movement in this picture is overly exaggerated. A green circle is to depict the location of the palatal surface of the maxillary cuspid tooth. The red line inside the green circle usually confines the limits of normal chewing.lateral excursion with green circle

I have learned to appreciate the following kind of a staunch red line that the occlusion foil marks to the palatal aspect of the cuspid teeth of my patients. This video shows what I do to treat patients with occlusion problems.

The points of interference in the back teeth area are very difficult to distinguish from occlusion bearing points of contact. Nevertheless, it is those almost undistinguishable wispy dots that have to be removed in order to obtain a staunch red line, the hallmark of proper canine guidance. Personally, despite my 30 years of practice, I must admit that I almost always fail to identify the right ink mark to grind unless I compare the foil marks to a Tscan movie. With an uninterrupted red line like that on the palatal surface of this young lady above, however, gives me a confidence that I have eliminated all the disturbing contacts of the back teeth area. As confirmed by a Tscan movie the lateral excursion test for this young lady showed smooth gliding of the mandible, uninterrupted by interferences. As a result, she was set free from her almost daily bouts of migraine. Clicking in her jaw joint also disappeared. I have been following the condition of her occlusion at recall visits. She still is very happy of having received the treatment a couple of years ago. The occlusal alterations that I performed have remained unaltered, as if the natural harmony of muscles and dentition would be a self-repairing system itself.

I have examined thousands of Tscan-movies of the lateral excursions of my patients. I have concluded, that would there be a slightest interference of the back teeth, a jaw-elevating reflex ensues. A minuscule tactile contact between the back-teeth during the lateral glide of mandible fires a powerful burst of activity in the masseter and temporalis muscles. The interference produces a jagged total force curve on a Tscan force vs. time graph. The activity of elevator-muscles shuts down the activity of muscles that exert lateral movements. The time required for the mandible to disclude the back teeth is prolonged.

In the natural chewing cycle the same things happen as with the lateral excursion test, but it happens vice versa, in an opposite direction. The smooth return of the mandible from lateral excursion into the midline is hampered by the slightest interference in the back-tooth area. The reflex activity of the two powerful elevator muscles ensues and the antagonistic medial pterygoid muscle is turned off. The mandible can’t glide smoothly to the maximum intercuspidation. A jagged up-lateral-up-lateral stepwise jaw-closing ensues, depending on how many times the anterior guidance of the mandibular path-of-gliding was interrupted by back-tooth interferences. The chewing doesn’t proceed smoothly, but it appears awkward and strained.

To understand the movements of the mandible, it is essential to understand the direction of the muscles involved in the process. The medial pterygoid muscle is commonly thought to belong to the “elevator” group of muscles, which I think is is a misnomer. The medial pterygoid exerts a mediotrusive direction of force which is mostly perpendicular with the direction of force of the masseter muscle. The fibers of the medial pterygoid point almost directly in the opposite direction of most fibers of the temporal muscle. The antagonistic nature of the masseter and temporal muscles in relation to the medial pterygoid is a fact of anatomy. It is misleading to put the medial pterygoid muscle together within the jaw-elevator group of muscles. Besides, even the sensory control of  its activity is emanating from an entirely different place – the sensory endings of the anterior teeth.

To resume the title of this article I would conclude that the general physical activity is no less harmful for the muscles of mastication than it is for the rest of the body muscles and joints. However, the occlusal interferences of the dentition disturb the smooth and effortless action of the jaw muscles in a similar manner as your walking would be hampered by a pebble in the sole of your shoe.

Instead of instructing our patients to stop chewing, it is a much better idea to take away the interferences of dentition and let the muscles do the thing they best want to do. Take the pebble out of the shoe. The trouble, of course, is to find out where the pebble lies in the dentition. Experienced dentists admit that it is not easy to make a filling to match perfectly to the lateral chewing movements. Traditional occlusion foil technique just does not always do the trick. Implementing digital technology into our everyday practice to detect and record occlusal contact force alterations in vivo sets the quality of dental work to a new level of standard.

 

Chewing gum. Details of the process and a remark on its social implications

Take a good look at the following link that takes you to an image of the temporal muscle in the Wikipedia:Wikipedia Temporal Muscle

The motor units of the many muscles that move about the mandible are pointing out to every possible direction. I would like to point out that they can’t be active, all of them, simultaneously. Agonist and antagonist muscles don’t work at the same time.  Like the rest of our body, muscular activity in one direction switches off the activity of other muscles that would have an antagonistic direction of force.

Then, open another browser window from the following Wikipedia link:Wikipedia Medial Pterygoid Muscle

Put these browser windows side by side on your computer screen and watch. It is easily understood that the medial pterygoid and the temporal muscles are antagonistic for each other, for the most part of their respective motor unit fibers. Both these muscles are the elevators of the mandible and they should be the main agonists in the process of gum chewing. However, simultaneous operation of these two muscles is not possible. The most part of temporal muscle fibers would be drawing the mandible up and back. This movement conflicts with the most part of fibers of the medial pterygoid muscle, that are almost directly opposite, but at least perpendicularly oriented to those of the temporal muscle. There must be a mechanism that prevents a force-directional conflict between these two muscles.

There is a simple solution – timing. The point of interest is the timing of the burst of activity in each of these two muscles.

The temporal muscle and the medial pterygoid can never act simultaneously. The temporal muscle moves the jaw up, the medial pterygoid moves the jaw medially, but whenever the other one is active, the other one can’t be active. One after the other: first the jaw moves up by the activity of the temporal muscle, then the jaw moves medial by the activity of the medial pterygoid muscle. We normally like to see the gum-chewing to happen in a smooth lateral swing of the mandible from lateral excursion into the maximum intercuspal position: Alaleuan liikesuunnat sulkemisessa

Looking at the jaw-closing phase of the chewing process in detail, however, there can be just two main directional muscular force vectors happening, up and medial. These two events don’t happen simultaneously. A slow-motion presentation would show a stepwise locomotion of the mandible as follows:Alaleuan liikesuunnat sulkemisessa osissa

I am a dentist, but that’s not the only reason I like to watch people chewing. The ability to chew is, in fact, a social skill. Amicable social cohesion in a group is best created at a dinner table. The jaw movements of the table-mates pace the discussions and the social atmosphere of the dinner group. Not sharing the dinner, not showing one’s jaws moving, would cast an individual outside the dinner-table group society. Take yourself a break and watch the following YouTube video in a separate browser:Beldent Casi Identicos chewing gum ad

It is a commercial advertisement by Beldent chewing gum company. You could see identical twins chewing gum. Take another careful look, and see how individual people deal differently with their jaw muscles while chewing gum. Others have broad lateral excursions of their mandible, whereas others seem to be careful just to move their mandible carefully up and down. The police sergeant in this video seems to me to present the sort of confident, assertive smoothness of his jaw movements.  He has got a beautiful lateral swing of his mandible closing in. First, the temporal muscle seems to squeeze completely the chewing gum bolus, after which the medial pterygoid draws the jaw back to the middle.

In contrast, the young man in white pullover seems to me to be unconfident in his jaw movements.

There are those less fortunate individuals who seem to be more cautious in their jaw movements. First, they do the initial crushing of a part of the bolus, then they move their mandible a little bit to the middle direction, then a bit of crushing-down again, then again the jaw movement proceeds a little into the middle. To me it looks like the white pullover guy would feel uncomfortable, as if he would have difficulties to decide whether to chew his gum or not. In a dinner table, it could be interpreted as if this young man would have difficulties to accept the same food that the rest of the table-mates are enjoying. A social stigma.

Yet I believe, the inability to chew smoothly for this white pullover guy and his co-sufferers, is not so much about the dynamics of social group behavior, it can be better explained by the difference in the anatomy of the dental arches of these individuals. The difference in chewing patterns between the police officer and the young man in white pullover is the result of how smoothly their opposed jaw-elevator muscle-force-direction-vectors are timed to co-ordinate.

In my previous articles in the www.blogbites.net I have already explained how the sensory information between the back teeth and the front teeth differs. The sensory information from the back teeth stimulates the temporal muscle, whereas sensory information from the front teeth switches off the activity of the temporal muscle and causes a burst of activity in the medial pterygoid muscle instead. The anatomical set-up of teeth on dental arches determines and guides the activity of the agonist and antagonist muscles of mastication. I have also discussed these matters in my previous articles, such as “Filibustering in the House of Parliament of Occlusion” and “Anterior guidance illustrated”. Sign up to follow my blog. Forthcoming articles discussing the details of jaw-closing business are underway.

Anterior guidance illustrated

Right now, I am preparing a presentation for a continuing education course. I have been granted a couple of hours to present my ideas to my colleagues at the premises of the campus of the University of Jyväskylä. I am going to present a novel hypothesis that the anterior teeth provide different kind of sensory information as compared to the back teeth. This idea provides a theoretical basis for the so called canine guidance phenomenon. The dissemination of this idea will cause a revolution in occlusion -related clinical guidelines.

The muscles attached to the mandible are pointing to many different directions. The direction of the motor units of the many muscles are often antagonistic. It should be self-evident that in the different phases of chewing sequence a concerted guidance of activity of different muscle groups are required. I should have to make my audience convinced that the oppositely directed forces of different muscles of the mandible must be monitored and controlled by automatic sensory reflexes.

The town of Jyväskylä has historically been regarded as the cradle of education and learning in Finland. Jyväskylä has been cherished with a moniker “The Athens of Finland”. As the freemen of Athens, so shall I be encouraged by the spirit of pursuit of knowledge, that is so valued in Jyväskylä.

To make a slide show for my presentation is a challenge. My presentation is about the dynamics of mastication; it is about how the jaw bone moves about by the action of muscles. Such an automatic, common thing that normal people would little care to discuss about. Yet I should have to speak about the subject for the whole night! It would be difficult, and probably boring, to try to set out the spatially three-dimensional phenomenon of mastication cycle into its fourth dimension, i.e. the time, just by means of narrative of words. I shall need some pictures to make my point.

Obviously, I turned over to Google Pics, and offered her a variety of my favorite search terms. Yeah, she provided me with some feasible portraits of skull bones and jaw muscles, but not quite what I had wished for. Believe me, a facial view illustration of the lower jaw positioned in slightly lateral extrusion, with the teeth and mandibular bone informatively glowing through the skin is a rarity even in the vast and infinite expanses of the worldwide web. Besides, should I use the search result pictures, there would be the elaborate copyright-permit-issues to deal with.

Ultimately I could not find any other way but to go to the stationery across the street of my practice and buy some paper and ink. What a Saturday! Several hours of toiling, ink stains on my face and hands, but the process of drawing ascertained myself of the importance of my work. The illustrations make the importance of canine guidance to become self-evident. The idea of anterior teeth guiding the movement of the mandible in mastication is so simple and makes so much common sense, and yet it is so very difficult to verbally explain this idea for the uninitiated.

Here’s the illustrations that I created. I hope they make my hypothesis clear. Here’s how the important events take place in the jaw-closing process.2017-04-22-11-00-55

In the figure 1. there is a lateral view of the skull crushing a piece of jelly-bear-candy between the molar teeth. Only the molar teeth are receiving mechanical strain from the piece of candy. Note that the anterior teeth are not in contact. This two-dimensional picture can’t show it, but you can assume that the mandible is slightly in excursion to the lateral, to the working side. The sensory information coming from the molar teeth under pressure load provides a signal for the masseter muscle. The masseter must “GO!”

2017-04-22-11-53-42.jpg

The next figure 2. is a facial view of a pale-faced gentleman in the action of squeezing a jelly-candy between his left molar teeth. The blue arrow pointing upward shows the direction of forces that are moving the jawbone. The principal muscles that are active in this process are shown in orange color. On the left side of this gentleman the temporal and masseter muscles are active. Contralaterally, in the non-working side, on his right side, the pterygoids, the lateral and medial provide the thrust to keep the mandible to the working side. The orange circle depicts the inevitable about-to-happen point of contact between the left upper and lower canines

2017-04-22-10-59-52

Figure 3. shows the moment as the left canine teeth of the working side meet each other as the molar teeth approach each other on their way through the jelly-candy mass. Now, the upper and lower left canines make a sharp contact and there is sensory information coming from the canines. The blue arrow indicates that the information coming from the canines signals the masseter muscle. The masseter must “STOP!” it’s activity.

2017-04-22-11-53-03.jpg

Figure 4. is to illustrate that after the signal provided by the colliding left canines, a complete revolution has taken place what it comes to the activity of different sets of muscles. The signal from the canines has quieted down the activity of working side temporalis and masseter muscles. The activity of contralateral side pterygoids is no longer needed. The blue arrow below the chin shows the direction of mandible movement from the lateral excursion into the maximum intercuspidation. The only muscle that needs to be active is the medial pterygoid of the working side.

The point of my presentation is, that the mandible is not just a senseless inert nut-cracker-machine, but a sensitive organ providing two different kinds of information, depending from which tooth area the sensory information is coming from. The anterior teeth are crucially important to put off the potentially destructive forces of the masseter and temporalis muscles in the final stage of the chewing cycle. Previously held ideas of chewing and occlusion need to be revised. My forthcoming presentation in Jyväskylä 18th May, and my blog articles present some clinical implications of this paradigm. Eventually, there will be fundamental changes in many dental clinical treatment modalities.

Purennan uusi paradigma Jyväskylän kesäyliopistossa

HAMMASHOIDON AJANKOHTAISILTAPÄIVÄ:
KULMAHAMMASOHJAUS, SEN TOTEAMINEN JA MITTAUS
T-SCAN LAITTEELLA
Torstai 18.5.2017 klo 16.15–19.15, virkistystauko n. klo 17.30
Jyväskylän yliopisto, Agora-rakennus

 

Kouluttaja

Lauri Vaahtoniemi HLT
Sisältö:
Koulutuksessa käydään läpi olemassa olevaa kirjallisuutta ja tutkimustietoa siitä, kuinka hampaistosta lähtevä sensorinen afferentti hermotus ohjaa purentalihasten toimintaa, käytännön kokemuksia, kuinka purentaa ohjaavaa sensorista informaatiota voidaan mitata Tscan-laitteella.
Tscan-laitteen maahantuoja tuo laitteen paikalle ja sen käyttö demonstroidaan.
Hinta 60 € / osallistuja
Koulutuksen jälkeen on mahdollisuus osallistua omakustanteisesti yhteiselle illalliselle Hotelli Albaan, illalliskortin hinta n. 40 €
Ilmoittautumiset 1.5.2017mennessä
Ryhmäilmoittautumiset
kesayo@jyu.fi

Ilmoita ilmoittautumisen yhteydessä, mikäli haluat osallistua myös omakustanteiselle illalliselle Hotelli Albassa.

Lisätietoja
Jyväskylän kesäyliopisto, p. 044-760 3730
koulutussihteeri Hanna Rajala

Vaahtoniemi.Lauri3622

Hammashoidosta on tulossa halpaa lystiä SOTE-maakuntien hallintojen talouspäälliköille.

Purennan diagnostiikan uusi teknologia tulee vähentämään väestön hammashoidon tarvetta. Uusi ajattelutapa tulee olemaan terveysvaikutukseltaan ainakin samaa luokkaa kuin aikanaan oli fluorin ja ksylitolin merkitys kariessairauksien vähentämisessä yhteensä.

Paikkojen lohkeamiset ja hampaiden halkeilemiset loppuvat lähes kokonaan. Purentakiskojen tarve väestössä vähenee murto-osaan nykyisestä. Purentalihasten ja leukanivelten ongelmat hoidetaan pysyvästi kuntoon. Toistuvasta päänsärystä kärsivien määrä putoaa huomattavasti ja migreenistä johtuvia sairaslomapäiviä ei työpaikoilla enää paljon nähdä. Hampaiden vihlominen vähenee. Yhä useampi akuutti pulpiitti parannetaan ilman kallista ja aikaa vievää juurihoitoa. Vertikaalisten ientaskujen säännöllinen ruoppaus kyreteillä jää historiaan. Hammaslääkärit voivat nukkua yönsä rauhassa, kun potilaiden valitukset mystisistä kivuista siltaremontin jälkeen jäävät historiaan.

Mistä on kysymys?

Tähän asti purentafysiologia on keskittynyt mittaamaan, mitä purentalihakset saavat aikaan ja miten hampaat ja rakenteet saadaan kestämään lihasten tuhovoimaa. Uusi digitaalitekniikka sen sijaan mittaa hampaistosta lähtevää sensorista informaatiota. Olemme nyt askeleen pidemmällä. Ymmärrämme paremmin lihasten toimintalogiikkaa ja voimme ennustaa, kuinka lihakset tulevat käyttäytymään. Hampaisiin kohdistuvaa painetta mittaava sensori osoittaa toimintahäiriöt purennan dynamiikassa. Voimme nyt ennalta ehkäistä vahingollisen ja väärään paikkaan kohdistuvan purentavoiman.

Tervetuloa tutustumaan näkemyksiini, purennan uuteen paradigmaan, jonka esittelen Jyväskylässä 18.5.2017. Muutaman tunnin iltakurssilla esitän katsauksen olemassa olevaan tutkimustietoon TMJ-ongelmista ja kulmahammasohjauksen merkityksestä. Perustelen, miksi bruxismi ei oikeastaan ole sairaus, vaan oire. Esitän hypoteesin, kuinka alaleukaan kiinnittyneet, moneen eri suuntaan vaikuttavat eri purentalihakset saadaan toimimaan ristiriidattomasti. Kerron esimerkein, kuinka potilaani ovat parantuneet vaivoistaan. Perustelen myös näkemykseni, miksi kreivi Draculan kulmahampaiden täytyy olla tarua ja luonnotonta kauhistusta.

Voit ottaa mukaasi vanhat uskomuksesi siitä mikä purennan hoidossa on potilaillemme parhaaksi, keskustelemme sitten kurssiin jälkeen illallisella, ennakkoluulottomasti ja pelkäämättä tieteellistä vastakkainasettelua ja väittelyä. Voit valmistautua esitykseeni perehtymällä tässä blogissa kirjoittamiini artikkeleihin.

Tiede on keskustelua ja totuuden etsimistä, joten annetaan sanan miekkojen kalista!

Of Jaw-Clenching, and a Remark on Open Bite

Then the king told the attendants, ’Tie him hand and foot, and throw him outside, into the darkness, where there will be weeping and gnashing of teeth.’

– Matthew 22:13 –

The normal complaint of bite-problem patients is that they say they don’t get any rest for their jaw muscles. They are resigned and miserable and they try to stay alert to follow the good advice of deliberately keeping their jaws apart, their teeth separated. However, they constantly find themselves clenching and gnashing their back teeth. That’s human nature.

The jaw does not just hang out there all day long, waiting for meal times to provide for bits to chew on. The swallowing reflex is another important business of the occlusion system. Every 30 seconds, or so, we do a swallowing reflex and that’s when the teeth make contact.

Initially in jaw-closing, the mandible may be hanging freely to the left or right, front or back, according the tilt of your head. Normally, the jaw closing muscles bring the mandible slightly forward so that the initial cautious contact between the upper and lower dental arches happens in the front teeth area. Excess force on a single front tooth slows down the jaw-closing and the mandible is steered to a more convenient position with more and more evenly distributed tooth-to-tooth contacts. Whenever the back teeth sense first contact, once again the jaw-closing muscles go more active. As soon as the back teeth make their first initial contact, it is very hard to deliberately stop the jaw-closing.  After the teeth are set together in the maximum intercuspal position, the power thrust of the closing-in muscles reaches the maximum. The tissues yield to tooth contact forces. The teeth are bent in their sockets; the periodontal ligaments of the teeth are squeezed. The bony structures in general, are bent. Even the teeth themselves undergo torsion and strain. Thus, the power of the jaw muscles becomes exerted to the front teeth, that yield under pressure. This is the moment after which, the forceful action of the jaw -closing muscles is suddenly repealed. The increasing sensory afferent information from the yielding front teeth stopped the clenching activity of the temporal and masseter muscles. Now, the deglutition reflex can proceed on. The jaw-closing muscles can relax and get their half a minute’s rest until the next oral phase of the swallowing cascade.

Unless, you happen to belong to the unfortunate patients that have been doomed to be outside in the darkness, weeping and gnashing your teeth. What went wrong?

Clenching one’s teeth is a disturbance where the sensory information from teeth fail to guide our muscular reflexes. There is a fundamental qualitative difference in the resultant muscular activity depending whether the sensory information to the motor ganglia of the trigeminal nerve is coming from the front or the back teeth. If your front teeth fail to give a signal to stop closing-in activity, you are bound to continue biting hard. The back teeth don’t differentiate what they are chewing on. They don’t give in. They go tough against anything hard. They do the same thing, no matter whether you are biting on a piece of carrot or your own tooth. The back teeth continue biting tough and hard, trying to find a position for the mandible where the power of the muscles becomes targeted to the front teeth. They go on and on waiting for this signal to end the closing-in activity of the masseter and temporalis muscles.

In my practice, I find it easy to help my patients who complain of restlessness of their muscles and jaw-clenching. Almost always, either one or both of their upper and lower canine teeth pairs are not in contact with each other in the maximum intercuspal position. I normally correct the unevenness by adding a little composite to the palatal of the upper canines and then adjust the bite with bite foil and diamond bur, little by little, by making the patient tap freely until all the teeth occlude simultaneously. The clenching will be cured right away.

There is another interesting aspect of the deglutition reflex that I have met with individuals with open bite. People with open bite can’t stop the back-teeth-closing-in sensory input, because the front teeth do not meet at all. How can they stop clenching? How can they swallow at all? No worries, Nature has a plan for that. In the swallowing reflex, simultaneous to the power-clenching phase of deglutition, a cascade of events happens with the tongue. The tip of the tongue moves against the front teeth. The tip of the tongue adds the thrust against the incisor teeth. Individuals with open bite need to thrust their tongue much harder against the front teeth to make them yield enough so that a sufficient sensory signal can happen from the front teeth. The swallowing process turns into a vicious cycle where the tongue tip must be thrusted hard against the front teeth. The dysfunctional tongue activity happens every 30 seconds, and in the long run, it pushes and moves the front teeth further apart and makes it even harder for the anterior teeth to switch off the back tooth sensory input in the cascade of swallowing process.

The resilient yielding of tissues undergoing strain from muscles of mastication is a crucially important factor that determines the functional dynamics of the occluso-muscular complex. The tissue-yielding-factor can’t be accounted for in studies employing mechanical articulators and stone-cast models of dentition. Even modern-day three-dimensional computer-created imaging of occlusion dynamics fail to account for the impact that the minute tissue-yielding can have for the resultant sensory information coming from the teeth. The Tscan system, however, provides the clinician dentist with an insight of events that happen in vivo. Perhaps, the tissue-yielding-factor has not been an easy and obvious thing to demonstrate on dried skull bones in the study-rooms of anatomy departments, where hypotheses of mastication dynamics have been contemplated. I can’t resist the temptation to finish this article with another biblical quote about the dry bones:

Thus says the Lord GOD to these bones: Behold, I will cause breath to enter you, and you shall live.

– Ezekiel 37:5 –

 

Bruxism. Etiology and Treatment.

Broken fillings, fractured teeth, the bite is out of balance. The dentistry bills make a substantial part of this person’s family budget. He/she has come to my office because of having learned somewhere that I should know something about the bite issues. I’m supposed to belong to the cognoscenti, can I help?

These patients go in two categories – the ones with good TMJ-joints and the ones with bad joints. Both categories receive the same treatment. I adjust the bite forces as explained in my previous article “The Soundbites of Sound Bites”. I am quite confident that with a micrometer or two grindings here and there, guided by frequent Tscan recordings, I am capable to create a perfect, digitally verified match between the teeth of the upper and lower jaw. I would not touch my diamond bur if I would not have a Tscan in my office. It is so many times that I have fooled myself to rely only to the looks and appearance of bite foil markings. The digital data of occlusion forces is so much better a tool to accurately level out the high force contact points. I change the shape of the occluding dentition so that when the patient closes the teeth, I can hear a nice relaxed click of the upper and lower jaw teeth meet each other almost simultaneously. If I can make the jaw closing relaxed and easy, I am assured that the jaw joints are lying in the condylar fossa in their most favorite and stable position. The power-clenching phase of jaw-closing produces a stable total force curve close to the 100%

Despite my efforts to equilibrate the shape of occluding surfaces I frequently meet patients whose lower jaw has trouble to meet the upper jaw. It is not only the shape of the occluding teeth that makes a difference. The next video is from a patient with problems with his joints. Despite repeated efforts I have not been able to completely cure his problems. However, during the last 6 months of my repeated interventions we both agree that there has been improvement. Here’s how the jaw-closing looks like for him:

In this recent video, it takes 0.59 seconds from the first, initial tooth contact “A” until the time point “B”, where the maximum amount of contact points has been attained. Looking at the video you see how the jaw-closing muscles are working on to do the adjustment. The pillars demonstrating the actual forces in different points of occlusion are pumping up and down in each 3-microsecond timeframe of the movie. There must be slight translation of the condyle joint surfaces during the final millimeters of rotational closing of the mandible so that the teeth would fit together. We are hoping that his joints gradually get better and better. Before and after I perform any intervention on the teeth of my patients, I always palpate the jaw-joints by putting my finger-tip into the ear canals. For some individuals, I can feel the synovial tissues moving and bulging the wall of the ear canals while patient closes the jaw. For some I can feel the “click” sound of the synovial disk, sometimes there might be crepitus or excessive lateral deviations of the joint during the closing movement. I try to make a verbal description of what I am feeling with my fingertips. Very often the fingertip feel of the joints can be perfectly normal, but the digital data produced by electronic pressure sensors between the teeth reveals that the joint can’t be rotating normally. My experienced fingertips give me some idea what is going on, but my fingers are not a tool reliable enough to assess the quality of jaw joint.

Nevertheless, I can make almost everybody to close their jaw smoothly, with a minimal time elapsing between the initial, first contact until the maximum amount of tooth contacts in maximum intercuspal position. The patients themselves usually immediately recognize an improvement of their bite. Their usual comment is that now they are biting more “freely”. However, I can’t get a perfect stable 100% total force curve for every one of my patients. The jaggedness and wobble of the total force curve reveals that there still is muscle strain oscillating between different groups of jaw-closing muscles during the clenching period. These are the patients with a bad bite, an underlying joint problem. Instead of a stable rotation, there happens a slide of the joint surfaces during the last millimeter of jaw-closing. Instead of a rotational final stage of the closing movements, there is a subtle translational component in their joint movement. Despite that there is a stable occlusion in the tooth-to-tooth-end of the jaw-swivel-system, the muscles are strained to keep the joint-ends stable during the power-clenching phase of jaw-closing. The sliding of the joint surfaces produces a total force curve that is unstable, jagged and wobbly.

After I have finished working on the jaw closing, an equally essential step in my treatment protocol is to ascertain that the lateral excursions should be strain-free for the muscles. This is important both for those with stable joints as well as for those with problems in their joint function.

Normally, I reshape the canine teeth to make the premolar and molar teeth disclude immediately as the mandible starts to glide laterally. Some grinding down of the cusp inclines of the back teeth are usually also needed. For individuals with a healthy TMJ-joint system, it is relatively easy to attain a beautiful Tscan recording, with a characteristic appearance.

The total force curve raises steeply after the time point “A” -the first contact point – to the time point “B”, where all the contact points have met. The three-dimensional graph of occlusion shows the bite forces evenly divided on all teeth and a stable total force line appears close to the 100% level all through power-clench phase of occlusion from the time points little after “B” and lasts until the time point “C” on a Tscan -graph. The lateral excursions happen quickly and smoothly between the time points “C” and “D”. The pillars showing the amount of relative force on premolars and molars disappear. The total force falls to zero as soon as all the force is subjected only to the working side pair of canines. There are now wobbles, nor jaggedness in the total force curve. Each group of muscles seem to know what to do and when to do. There are no disputes between the differently oriented motor unit fibers.

Again, with individuals with joint problems, it may be impossible to make their back teeth to disclude in lateral excursions. The joints seem to be sliding off their axis during the rotation, which can be seen on the Tscan as the contact force hops off the canine to move over to the back teeth.

All the data is saved in my computer files, easy for display. I can explain and inform my patient that I can see what the problem is. With the interventions explained above, I can relieve the muscular strain that has been damaging not only for the dentition, but also to the joint tissues. Effortless jaw-closing and relaxed anterior guidance in lateral excursions of the mandible relieves the strain to the joint tissues.

The healing of damaged joint function takes time and it requires regular, repeated follow-up of my patients. However well I adjust the bite of these individuals with the Tscan, it is not uncommon to see signs of attrition and tooth wear already months or only weeks later. Like a door with broken hinges, the door frames wear out quickly. Likewise, the wear-out of the anterior guidance must be regularly assessed and repaired in individuals with slackness in their jaw-joint-hinges. I also advise my patients to avoid chewing anything unilaterally, but always to pay attention to share the bolus of food to be chewed equally with both sides of the dentition and do the chewing by up and down movements only, because the lateral excursions would strain the working side condyle and might eventually slide it off its rotational axis.

The description of patients above falls in to the broad category of what clinician dentists call bruxism.

A search through PubMed database of scientific journal article abstracts dealing with bruxism shows that the overwhelming majority of present day authors reject the idea that occlusion should have any critical role in this entity. Actually, the International Code of Diagnosis (ICD-10) for bruxism, F45.82, is classified in the chapter V, which deals with mental and behavioral disorders.

In my previous article “The Legend of Spooky Bites” I criticized the prevalent attitude of the mainstream of occlusion scientists. Surely, we all agree that muscles do not operate like if magic, just by themselves, without any reason. The activity of jaw muscles is a result from efferent motor nerve activity from the ganglia of the brain stem. What makes the ganglia vibrate, we would like to know.

Basically, the question is whether it is a simple mechanical reflex or would there be higher spirits that make the jawbone move. I question the view, that the jaw-moving muscles would essentially be guided by some complicated phantomlike actions of our psyche. By no means, there may be some truth there – just think about it. You enter a music club, where the beat of rhythm overwhelms your soul and the music syncopates your nervous system so that the agitation can make you tap your feet and clap your hands. A good piece of music surely can make your jawbone jerk, but really, the instability of the occlusion and jaw-joint is a much better explanation for this perplexing jaw-muscle hyperactivity.

As of yet, most of the data in studies of occlusion is not based on digital measuring of occlusion forces. With a Tscan in my disposal, I can see things that have not been recognized earlier. New technology has opened up new avenues of understanding the tooth grinding phenomenon. I present a hypothesis for discussion that an unstable and jagged total force curve during clenching period in a Tscan recording is a physical demonstration of pathology in the jaw joint system and most likely it is a common feature for patients with pathological tooth grinding. The unstable joints slide and translate during the jaw-closing. As a result,the perfect occlusion is lost and the muscles are activated for a search of a better and more secure hold between upper and lower jaw. The rapid actions of different sets of jaw-moving muscles are projected as a jagged total force curve with notches and peaks of opposite force directions oscillating back and forth within microseconds of intervals.

The jagged total force curve in Tscan recording reflects of a tug-of-war going on between different groups of jaw-moving muscles, a feature that is typical for a subset of patients that suffer from excess teeth grinding. Any dentist with a Tscan can see these signs. The prevalent thinking by the mainstream of occlusion scientist, that bruxism is a mental or a behavioral disease should be challenged. Bruxism should be regarded as a reflex or as a symptom of failure in occlusion, not as a disease itself.