What Really Causes Cavities: A Systemic Approach To Decay And Understanding Dentinal Fluid Flow

Sometimes it’s easy to forget, but teeth are vital living structures in your body. A healthy tooth has a blood supply, and an immune system, just like all other organs. That means that teeth have metabolism too!

We have all heard that eating and drinking too much sugar or acidic foods can cause cavities because it exposes the teeth to an unfavorable environment. But what if only part of that is true, and for a different reason than we’re taught? If you’re frustrated because you feel like you’re eating right, brushing, flossing and doing everything to prevent cavities and still getting them, then read on. There is more to it!

Dr. Steiman and Dr. Leonora are the pioneers behind the research of the endocrine system and how it relates to tooth decay. What have they discovered (after over forty years doing research) is that our bodies have many innate defensive responses built in to protect us. And, believe it or not, and our teeth do as well! The defense of our teeth can be attributed to the hypothalamic-parotid gland-axis and a normal dentinal fluid flow. I know it sounds complicated, but don’t worry, keep reading and I will break it down!!

Basically, teeth are made up of several components.

There is a nerve and a blood supply that connects to the blood supply in the jawbone. This blood delivers nutrients to the pulp, or the “heart” of the tooth. The pulp is rich in nerves and vascular beds. It nourishes the dentin and cementum, which are the inner softer materials of the tooth which contain tiny microscopic tubules (called dentinal tubules) full of fluid.

The enamel is the hard protective layer on the outside of the tooth. In a healthy tooth, the blood supply comes in, brings nutrients and delivers them the pulp, which then keeps the nutrients flowing from the inside to the outside of the tooth through the dentinal tubules.

This process is called dentinal fluid flow (or DFF).

In essence, think of DFF as “sweating.” When the sweating of a tooth is halted or reversed, it starts to decay since the tooth will internalize bacteria and sugar. The function of the dentinal fluid flow is to prevent the influx of bacteria and acid into the tooth. In addition, the slightly basic pH of dentinal fluid at 7.4 provides a buffer against acidity and prevents breakdown of the tooth.

How was this discovered? Well, Dr. Steinman developed a brilliant technique where he injected a fluorescent dye into the abdomen of rats, and observed the pathway dye took through the body. Incredibly, it only took 6 minutes for the dye to show up in dentinal tubules of teeth, and an hour to get into the enamel.

The radioactive dye was injected into the stomach, meaning it bypassed the oral cavity completely, yet still ended up in the teeth (site: Relationship of Fluid Transport, pg 12) within 45 minutes. This systemic effect was also seen when injecting sugar. Bypassing the oral route of sugar ingestion indicates how sugar has a cariogenic effect from a systemic action. (pg 12)

Yikes.

An article published in 1958 was Steinman’ first suggestion that cavities were related to “circulation” of the dentin. Disruption of the metabolic cycle causes a disruption in the tooth metabolic cycle.

This makes sense, given that our entire body is all connected, right?

So what reverses the dentinal fluid flow and causes a disruption in the tooth metabolism (DFF)?

There are many mechanisms that can reverse or interrupt the DFF:
1. High sugar intake
2. Stress
3. Lack of exercise
4. Nutrition
5. Salt
6. Hormones
7. Saliva
8. Streptococci

Let’s dive into each of those a little bit.

1. High sugar intake: This is especially true of refined sugar, which when too much is ingested reverses the DFF. The DFF was in the rats was normal when no sugar was present in the diet. It appears that the parotid gland, in the presence of sugar, inhibits the dentinogenesis (cell workers just outside the tooth blood supply.)

It is also interesting to note that complex starch does not cause the same cavity rate as simple sugar. Animals receiving added sucrose compared to animals receiving lactose and water had twice the rate of caries. Lactose is absorbed more slowly and hydrolyzed differently than simple sugar, and did not cause the marked increase in caries in post-eruptive teeth (pg 98)

A deficiency in phosphate is associated with increased caries. Interestingly enough, further studies show that animals had a 20-30% decrease in phosphate when sugar was administered. During development, this caused a 10% decrease in phosphate levels in teeth occurred during sugar administration. Phosphate deficiency may be caused by an excess of sugar. In order for carbohydrates to be broken down, the body must phosphorylate them to be metabolized. (98)

2. Stress: In the physical body, stress can be related, and cause electrolyte imbalance. In normal tissues, there is about 4x the amount of sodium outside the cell as found inside the cell, and about 18x the potassium inside the cell as outside.

For many reasons, this metabolism can be altered since it is dependent on the availability of SH groups, the abundance of ATP, and normal acetylcholinesterase. Undue stress in experimental animals has shown to cause the fluid inside the cell to become more like the fluid outside the cell, and this reduction in gradient can negatively affect normal cellular metabolism. Also, deficiency of certain metabolites can alter cells normal selective permeability. (pg33) Deficiencies in the following were shown in experiments to increase the risk of caries: phosphate, pyridoxine (b6), pantothenic acid(b6), and protein.

3. Exercise: It was found in a study comparing immobilized rats vs. exercised rats that the cavity rate was dramatically different between the two groups. It seems lack of exercise may have a profound effect upon decay resistance.

4. Nutrition: I am not going to go into details about what diet is the best diet, for it is beyond the scope of this post and is unique to every individual. However, there are studies that clearly show that too much sugar, lack of protein, lack of b5, b6 vitamins can contribute to decay.

Too much sugar is especially damaging because it causes micronutrient deficiencies. Sugar is absorbed much more readily and rapidly than starch, creating a deficiency of micronutrients which was demonstrated by the greater amount of dental caries in diets higher in sucrose compared to a diet which was equal in the amount of starch.

5. Salt: Certain chemicals can affect chloride in cells can play a role in cavities. In fact, it appears that large amounts of salt may be the reason behind increased cavities in modern civilizations! Increases in salt in a diet can cause an interference with the normal metabolism of teeth. (But unprocessed sea salt contains important minerals, so don’t worry about sprinkling sea salt on your plate in moderation!)

6. Hormones: The endocrine axis related to dentinal fluid flow is called the HPEA axis (Hypothalamus-Parotid gland Endocrine Axis). There are studies dating back to 1934 (Ogata) which proposed salivary gland endocrine theory after noticing bovine salivary glands exhibited hormone-like activity. Later studies, done on rabbits, show that the parotid gland is under direct control of the hypothalamus. Additionally, further studies were needed to investigate whether the parotid hormone may stimulate the health lymph flow, or “sweating” of teeth. I’ll try to simplify this theory:
Dentin (the inner part of the tooth) is made of very tiny tubes that go from the blood supply (pulp) to the outer layer of the tooth (enamel). At the base of this dentin is a layer of “shift worker cells” which are responsible for creating dentin and maintaining it. Teeth are living vital structures and have physiological needs like blood supply, but the extension of dentin limits the blood supply. In order to overcome this, the main blood supply in the body has extensions with windows for the pulp- so nutrients can diffuse out of major circulation and into the pulp chamber. These worker cells possess a dentinal fluid flow transport mechanism that constantly bathes the dentin with nutrients from blood coming in.

The kicker here is that the uptake of nutrients appears to be dependent on the parotid hormone(PH). PH can alter the permeability of worker cell membranes, which can inhibit or enhance nutrient uptake by the tooth. In addition, the odontoblasts contain an additional mechanism that allows them to act like a pump, so DFF is centrifugal in motion. Fluid/lymph will eventually reach the enamel and form a fluid layer. Because the hydrostatic pressure inside the tooth is greater than in the mouth, the tooth has a built-in defense system against bacteria and caries. When the DFF is compromised, cavities can occur.

7. Strep: there are several strains of bacteria that are more cariogenic than others. Strep mutans and it’s closely related friends are one of the primary caries causing bacteria. The bacteria adhere to the tooth surface and form a biofilm. Interestingly enough, a lot of people also have strep overgrowth in their guts. What you swallow can make its habitat in the gut as well (source).

Well, that was a lot of information! However, it’s so important to see how your diet, stress, and hormones all relate to your oral health. As stated in Steinman’s book, Dentinal Fluid Transport, “Beyond changes in digestion, alteration of intestinal function and accompanying a loss of appetite, a change in the water transport system potentially affects every cell and fiber of the system. Perhaps the basic answer to dental caries [cavities] prevention is a total way of life including sound nutrition, freedom from undue stress, regular exercise, fresh air, sunlight, and water intake.”

So give yourself a hug, take a deep breath, and go outside and enjoy this beautiful day!

Kristen Graham

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