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The mouth is a test tube

And you are the chemist. Practical advice on manipulating oral chemistry.

By Dr. Douglas Young

The set-up:  “No physician would treat a patient without a disease diagnosis and a medication (if needed) to treat that disease. Now dentistry has finally arrived at the place of treating the disease Caries with a diagnosis and medication. Dr. Doug Young, one of the world’s leading researchers in caries management, shares a course of action for every dentist to take in treating the world’s number one disease.”—Dr. Joe Whitehouse, Team Lead

FACT: Teeth dissolve in acid. It is a major problem dental professionals must deal with on a daily basis, whether it is a cavitation from bacterial generated acids, erosion of exposed root surfaces or more drastic destruction from stomach acid.

These problems often are treated solely with a restorative approach. Have a cavity? Get a filling. Have excessive wear on the occlusal secondary due to acid? Get several crowns. Cervical erosion? Place a Class V. This surgical approach will not stop this problem, and in fact, your work will be adversely affected if left untreated. Demineralization is all about the chemistry of the oral cavity.

It does not matter what specialty of dentistry you practice; if you work in the oral cavity and your work is bathed in oral fluid, then you have a responsibility to address this dynamic oral chemistry. In that sense, the mouth is a test tube and you can be the chemist who saves the day.

This article will review the science and logic behind the preventive and curative chemistry of CAMBRA, or Caries Management By Risk Assessment.

Know Your Acids

There are many sources of acid: bacterial, extrinsic (diet or environmental), and intrinsic (reflux, bulimia), and they can happen in any combination.

Bacterial generated acids (Formic, Lactic, Acetic and Proprionic acids) are weak small chain organic acids generated by a cariogenic biofilm in the pH range of 3.8-4.8. The size of these molecules is significant because they are small enough to fit into the diffusion channels of enamel and diffuse into the subsurface layer, causing mineral to be lost (demineralization).

This subsurface demineralization is first seen as a white spot lesion (see Fig. 1). The fact that the surface layer is still intact is clinically significant, because as long as the surface layer is intact bacteria are still too big in size to penetrate this surface, and we have the chance to remineralize the lesion.¹

Remineralization will happen if certain conditions are met. That is the beauty of chemistry. It is a science that is predictable as long as the recipe is followed correctly.

Obviously, for remineralization to occur, one must first stop the demineralization. This simple fact is quite often overlooked. Stopping the demineralization is done by raising the pH. In the short term, this is done by salivary buffers or oral products that raise pH.

In the long term, the makeup of the biofilm must be altered to a non-acid producing community and oral environment rebalanced to favor remineralization.²

The exact pH at which hard tissues will dissolve varies in individuals, but for purposes of this discussion, we can generalize that enamel dissolves at about pH 5.5 and cementum and dentin at approximately pH 6.2.

Simply put, you must neutralize before you remineralize. No amount of fluoride will help while the tooth is actively demineralizing. Healthy saliva in adequate amounts contains all the natural buffers to stop the demineralization process after a snack and maintain a neutral environment of approximately pH7. However, if the stimulated and/or resting saliva flow is inadequate or if the pH of the saliva is low due to lack of natural buffering agents, the patient will need help from oral products designed to raise the pH.

Unlike the weak organic acids produced by the cariogenic bacteria (pH 3.8-4.8), dietary acids (pH 3) and acids from the stomach can be much stronger (pH 1-2) and lead to surface dissolution (see Fig. 2) rather than subsurface dissolution. Surface dissolution cannot be corrected by chemical remineralization procedures. Once the surface is gone, it is gone for good. In that sense, treating the disease of dental caries gives dental professionals the unique opportunity to reverse and prevent this type of damage, whereas surface dissolution usually is not reversible.

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