Dentinal fluid transport - revolutionary theory of natural caries resistance and cariogenesis
Research by Drs. Steinman & Leonora posits the precedence of host resistance over bacteria as primary cause of tooth decay
While the official consensus regarding the causation of tooth decay points the finger at oral bacteria, plaque and concomitant acids as the causative agents in the formation of cavities, a minority of researchers has pursued a different - and highly promising - path.
The teeth - defenseless victims of a destructive oral environment?
"Maverick" researchers into the etiology of tooth decay started from the observation that the body is equipped with elaborate defense mechanisms allowing it to fend off invaders and destructive influences and thus preserve the health of all its other organs. Why would the teeth not have an inbuilt mechanism of self-defense as well?
Blood supply is the major route via which all organs are nourished and defended, and one major cause of disease and malfunction is restricted blood supply. In the teeth, the blood supply ends in the capillaries within the dental pulp, and it has been observed that restricted blood supply in teeth increases tooth decay.
Dr. Ralph R. Steinman, DDS, MS, professor of oral medicine at Loma Linda University, with the important assistance of Dr. John Leonora, professor of physiology and biophysics with a specialisation in endocrinology, are two outstanding scientists who conducted extensive and revolutionary research into the true etiology of dental decay based on the assumption of a self-defense mechanism existing in teeth.
Note: Sadly, most of Dr. Steinman's research into the dentinal fluid transport system and the etiology of caries was conducted on rats as well as a lesser number of rabbits and pigs1. A small number of studies done on extracted human teeth however confirmed their previous findings on animals. In the words of Dr. Steinman, “Every biochemical process of [tooth] decay identified in man is found to be identical in the rat. The only difference between the two is the speed of the reaction.” [which seems little surprising in light of the great difference in lifespan]
While the two scientists have frequently presented their work as a theory to be corroborated by further research in humans, considering the extensive evidence presented, Healing Teeth Naturally assumes Dr. Steinman's and Leonora's research results regarding the role of dentinal fluid transport, the hypothalamus-parotid gland axis, the high sucrose diet etc. in the causation and prevention of tooth decay in rats to be directly applicable to humans.
Teeth CAN and DO defend themselves: the central role of "host resistance"
Dr. Steinman and Dr. Leonora have indeed demonstrated - via more than a hundred studies carried out over nearly four decades - that teeth are able to fend off noxious outward influences and intruders (such as contaminating bacteria living off acid-producing foodrests). This defence occurs via the "dentinal tubular fluid flow", a continuous movement of nourishing interstitial liquid flowing from the dental pulp outward through the dentinal tubules and enamel and into the mouth.
It's only when this “dentinal fluid transport system” malfunctions due to various causes and via several pathways that a tooth will succumb to decay. In this scenario, cariogenic bacteria are simple opportunistic bystanders taking advantage of a condition of weakened resistance that allows them to invade and "conquer" a tooth. This is reminiscent of the insight ascribed to Pasteur on his deathbed who apparently admitted that "it's the terrain, not the germ, that causes disease".
Discovery and demonstration of the dentinal fluid transport system
As any dentist will learn in dentistry school, teeth are far from being solid structures. Instead they consist of an array of dentin tubules and enamel rods (see high-magnification dentin illustrations) as well as the pulp which is richly supplied with blood vessels, nerves, dentin-producing odontoblasts2 etc.
Intrigued by some of the early dental literature from the 1880s upward featuring research which showed that teeth might actually display a mechanism of self-defense against dental caries, Dr. Steinman set out to explore the theory. To this effect, he developed an ingenious technique involving the injection of a fluorescent dye (radioactive acriflavin hydrochloride) into the abdomen of experimental rats and observing the pathway the marker took in their body. What he found, was astonishing: the dye took just six minutes to show up in the dentinal tubules and an hour to reach the enamel. This discovery was tantamount to proving that teeth are active structures possessing a dentinal flow which moves fluid and substances contained in it from inside the body via the pulp chamber, the dentin-pulp interface through the dentin tubules and the enamel and eventually into the mouth.
Major functions and characteristics of the dentinal fluid transport system
Dr. Steinman found that this dentinal flux had two major characteristics with regard to bacterial acids and microbes present on the tooth surface (the "main culprits" for the destructive effects of tooth decay according to the conventional view). On the one hand, it prevented acids and germs from penetrating into the tooth, and on the other, its pH of 7.4 allowed it to act as a buffer to neutralize bacterial acids, thus carrying out a continuous self-cleansing action.
Another major function of this "tooth flushing mechanism" is the continual provision of nutrients derived from the blood essential for dentinal health into the dentin tubules via the blood vessels contained in the pulp chamber (dentin having no direct connection to the body's blood supply).
How dentinal fluid transport can be interrupted or
the genesis of tooth decay revisited
According to Dr. Steinman's research findings, while external contamination does affect the tooth, tooth decay starts when normal tooth metabolism is upset and fluid flow is interrupted, impeded, stagnating or even reversed. As the flow can be self-cleansing, it can also be self-contaminating. Dr. Steinman identified several pathways for this to occur, among them
- High sugar intake reverses dentinal fluid transport
- Stress can interrupt dentinal fluid transport
- Lack of exercise
- Lack of micronutrients
- Pharmacological agents
When no sugar is taken, the dentinal fluid flowed normally from within the pulp chamber outside. In contrast, no significant flow occurred in the presence of a high sugar intake. This effect was observed even after injecting the sugar directly into the lining of the abdominal cavity, i.e. completely bypassing the teeth.
Dr. Steinman thankfully seems to have just done one experiment where he stressed a group of rats (by confining them in a narrow cage which allowed little movement). Comparing this group to another fed an identical diet, it was shown that the stressed animals developed higher rates of caries. He summarised it as tooth decay being more pronounced when the system is “sympathetic dominant”.
Studying the effect of exercise on caries susceptibility, Dr. Steinman observed that when he placed two groups of rats on the same nutrient-deficient diet, the group that was exercised developed 4.8 carious lesions per animal while the non-exercised group developed a whopping 14.9. This result would indicate that exercise increased the dentinal fluid movement and/or quickly burned off the sugar circulating in the blood so it had no time to negatively affect the hypothalamus, the regulatory gland for dentinal fluid movement (see "How the fluid transport system mechanism works" below).
Dr. Steinman also noted that circulatory problems due to illness or declining health impacted dentinal flow, causing flow stagnation and reversal.
Compare "Copper, iron, manganese and other trace elements can halt/reduce tooth decay in rats" below.
After injecting bradykinin (a sympathetic compound) intraperitoneally into the experimental rats, Dr. Steinman observed centripetal (inward) movement of fluid in their teeth. In fact, the administration of bradykinin actually resulted in tooth decay in rats fed a non-cariogenic diet! Similar negative effects on caries rate were observed with the use of hydrogen peroxide.
Parasympathetic stimulants had the opposite effect, encouraging centrifugal (outward) dentinal fluid flow (compare "A pharmacological approach to preventing tooth decay" below).
How the fluid transport system mechanism works and which mechanisms control it
What is behind the normal and abnormal functioning of the "pump" involved in dentinal tubular fluid flow both in centrifugal and centripetal direction?
To find out, Dr. Steinman asked endocrinology professor John Leonora for advice. Dr. Leonora suggested to test the hypothesis of a hormonal mechanism behind dentinal fluid flow control.
And indeed, their subsequent studies demonstrated the existence of what they termed the "hypothalamic-parotid gland endocrine axis". The hypothalamus, an important control center for the autonomic nervous system (ANS), secretes a "parotid-hormone-releasing factor" when stimulated by eating, which in turn stimulates the secretion of a parotid hormone from the parotid glands (the largest salivary glands) which Drs. Steinman and Leonora managed to isolate in pure form from pigs. As shown by the researchers in their experiments on animals, this parotid hormone in its turn stimulates dentinal fluid flow by triggering the odontoblasts lining the pulp2 into action to function as pumps for the dentinal liquid.
Drs. Steinman and Leonora subsequently demonstrated that a diet high in sugar suppresses dentinal fluid flow by suppressing the proper functioning of this "hypothalamic-parotid gland endocrine axis" without which odontoblasts cease to pump dentinal fluid. In fact Steinman and Leonora managed to reverse the suppression of dentinal fluid flow triggered by the high sugar diet by administering parotid hormone to the rats and thus prevented tooth decay in up to 100 % of cases.
When odontoblasts stop pumping fluid, the hydrostatic pressure in the tooth/pulp is lowered and the normal fluid movement tends to reverse. Bacteria and other extraneous matter are drawn from the mouth (or the tissue that surrounds and supports the teeth) into the tooth/dentinal tubules via capillary action, where they cause microbial infiltration and biofilm formation.
Sugar and other cariogenic foods do not produce more bacterial acids than healthy food
In fact, in food-saliva incubation studies, Dr. Steinman found the very opposite to be true. Healthy foodstuffs, i. e. food containing numerous micronutrients and no processed items such as sucrose (table sugar), allowed oral bacteria to produce significantly higher amounts of harmful acids than the same amount of calories in the form of sucrose or glucose. Yet again, Dr. Steinman was able to furnish evidence that it is not the bacteria and their metabolic acids which are the major and first cause of tooth decay but the weakened state of the tooth (diminished host resistance) triggered by the systemic effect particularly of high sugar consumption as well as other factors (notably those listed above) which decrease dentinal fluid transport via their suppressive effect on the hypothalamus.
Some advice by Dr. Steinman regarding sugar consumption
If you "have" to have normal table sugar, only have it with a proper meal. Sugar eaten nearly on its own (such as in a candy bar) does not trigger the release of the parotid hormone which stimulates the outward flow of dentinal fluid and thus nature's inbuilt defense mechanism for teeth, which leaves your teeth defenseless when they need help (as they do during each act of eating).
When you "hide" the sugar in a proper meal, the parotid hormone will be released in a smaller or larger measure depending on percentage of sugar in your entire meal, its micronutrient content and also your personal makeup.6
Edgar Cayce's advice to never eat when upset etc. acquires an additional dimension here as well. Since stress suppresses the functioning of the hypothalamic-parotid gland endocrine axis (release of "parotid-hormone-releasing factor" followed by release of parotid-hormone), a meal taken under stress will also damage your teeth.5
Dr. Steinman's conclusion re the role of bacteria in cariogenesis and the true etiology of dental decay
“Local factors play a role,but they are not the initiating factors in dental decay...The first step in dental decay is a change in function” whereupon the movement of dentinal tubular fluid is reversed: from initially flowing from the pulpal chamber outward, it starts to flow inward from the oral cavity. The pulp chamber, followed by the dentin, become inflamed, with their constituent magnesium, iron, copper, manganese3, ATP/ADP, acetylcholine and sulfhydro groups gradually becoming depleted. Healthy tooth metabolism has ended, and the disease finally spreads to the enamel where it shows up as a cavity.
Rather than being a localised disease, tooth decay is in fact a systemic disease.
Copper, iron, manganese and other trace elements can halt/reduce tooth decay in rats
As mentioned above, Dr. Steinman found the loss of the minerals copper, magnesium, iron and manganese to be part of the process of cariogenesis3. By enriching a cariogenic (tooth-decay-producing) diet with iron, copper and manganese, he succeeded in reducing tooth decay.
In another study, a high sucrose diet was enriched with zinc, molybdenum, chromium, eggshell meal7 and carbamyl phosphate which produced a very dramatic reduction in tooth decay when compared with the rats fed only the cariogenic diet.
The dramatic impact of these trace elements may partially explain why seaweed and other sources of the complete mineral spectrum can be so helpful in assisting the health of teeth (and the body in general).
Several ways to prevent tooth decay?
In addition to the conventional approach to caries prevention which insists that it is acid-producing bacteria (streptococcus mutans in particular) which feed on sugar who create cavities via plaque formation and direct acid attack, there are several main "alternative" schools of thought regarding cariogenesis:
- nutrition: sugar, white flour, lack of vitamins and minerals lead to caries (Weston A Price, Herbert M Shelton)
- dentinal flux: interruption/reversal of dentinal fluid transport caused by high sugar consumption, stress and other factors leads to caries (preponderantly based on animal experimentation by Dr. Steinman)
- adding trace elements to balance high sucrose intake (as observed for instance in experimentation on rats by Dr. Steinman)
- stress and emotional factors (based on observation and studies of humans)4
To reconcile the various viewpoints or "angles of attack", it may be allowed to speculate in the following manner: since even the most ardent proponents of the "nutrition" school will admit that not 100% of individuals on the same nutrient-deficient sugar-laden diet will develop tooth decay or the exact same extent/location of it, it is conceivable that the "stress" factor might play a significant role by weakening the natural defenses of the human body4 and/or by interrupting the normal flushing action of the dentinal fluid as suggested by Drs. Steinman and Leonora's decade-long research on animals.
A pharmacological approach to preventing tooth decay (at least in rats)
In his studies with rats, Dr. Steinman found that injecting carbamyl (carbamoyl) phosphate or adding it to the animals' diet proved to be a potent caries preventative. It restored the dentinal fluid transport in spite of the ingestion of a high sugar diet, by reversing the suppressive effect sucrose has on the hypothalamus and thus stimulating the release of parotid-hormone-releasing factor. This amazing effect was further enhanced by adding trace elements to the diet.
Based on his rat studies, for preventing and controlling tooth decay in humans, Dr. Steinman extrapolated the required amount to be 150 mg a day.
Reception of the cariogenesis research conducted by Drs. Steinman and Leonora
While Steinman/Leonora's research has been stolidly ignored or even aggressively opposed by fellow scientists and dentist organisations alike (with some recent signs of a rekindling in interest however), it is permissible to wonder whether yet again, economic reasons are at the bottom of this ostracism. Which dentist indeed can make much money from telling people that their teeth are self-healing if properly supported? In fact, symptom-oriented Western conventional medicine in general doesn't "like" to think in terms of host resistance since it isn't very profitable (while expensive medication and surgery sure is).
Why aren't all teeth equally affected by caries?
While there are certainly morphological reasons for certain tooth types being more susceptible to caries than others, we have no explanation why for instance among several near-identical molars, there may be only one which has a cavity, while the adjacent ones can be in perfect health. This is (again) where "energetic" factors and schools of thought enter the picture, which assign specific roles and functions to specific teeth and where "energetic weakness" caused for instance by psychological factors can affect a tooth. One such system of thought is Traditional Chinese Medicine (TCM), another is the very detailed system devised by French dentist Estelle Vereeck. The latter (to date probably only published in French) quotes many observations of patients who for example developed (virtually overnight) caries in specific teeth upon undergoing specific traumas related to the "theme" associated with those teeth. The two major themes in Vereeck's system involve "father" and "mother" (childhood issues), while others relate to several additional important life issues.
Dentinal Fluid Transport
by Dr. Clyde Roggenkamp (Loma Linda University, 2004)
The above review of Drs. Steinman/Leonora's extensive work on the true causes of tooth decay cannot begin to do justice to the wealth of information provided in some 40 years of study by the two researchers. The book "Dentinal Fluid Transport" is the labour of love of a dedicated scientist who undertook to compile a detailed review of the numerous publications of Drs. Steinman and Leonora. His book illustrates the genesis of tooth decay centered around the dentinal fluid transport system and numerous ways in which the two researchers succeeded in reducing caries incidence. Includes a summarizing introduction by Dr. Leonora as well as an appendix with numerous tooth-friendly dessert recipes (incl. cakes) devised by Dr. Steinman who raised his three children on a healthy diet (which he concisely describes) without them developing a single decayed tooth.
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1 For Healing Teeth Naturally's stance on the question of animal experimentation, click here.
2 Odontoblasts are tooth cells arranged along the dentin-pulp-junction. (Quoting from Wikipedia:) "The odontoblasts secrete dentin throughout life (secondary dentin, once root formation is complete), which may be an attempt to compensate for natural wear of the enamel. Odontoblasts also secrete tertiary dentin when irritated. Tertiary dentin secreted by odontoblasts is often due to chemical attack, either by chemicals diffusing through the dentin and insulting the odontoblasts, or by diffusion of toxic bacterial metabolites down the dentinal tubules in the instance of a carious attack. This tertiary dentin is called reactionary dentin. This is an attempt to slow down the progress of the caries so that it does not reach the pulp. In the case of an infection breaching the dentin to or very near the pulp, or in the instance of odontoblast death due to other attack (e.g. chemical or physical), Pulpal Stem Cells can differentiate into odontoblast-like cells which then secrete the other kind of tertiary dentin, reparative dentin, underneath the site of attack. This is not only to slow the progress of the attack, but also to prevent the diffusion of bacteria and their metabolites into the pulp, reducing the probability of partial pulp necrosis."
6 Since Dr. Steinman only studied the effect of normal table sugar on the "hypothalamic-parotid gland endocrine axis", Healing Teeth Naturally has no information how or whether at all tooth-friendly sugars negatively affect the endocrine cascade. Since they are metabolised somewhat differently, it is possible that they don't interfere.
7 More about eggshells as a mineral "supplement" for teeth under Foods rich in minerals and trace elements (scroll to "Eggshells").