CARIES VS. EROSION

Claims and warnings of the ill effects of carbonated sweet drinks on dental health have occupied the minds of dentists and the concerned public for some time. In a recent, update one of the dental organizations warned of the harmful effect of the acidic drinks and the decay they can cause.

The acid that causes the demineralization in dental caries is a metabolic byproduct of cariogenic bacteria.  The acid that causes erosion, however, is either dietary, consumed as citrus fruits, vegetables, colas, carbonated drinks, or from the stomach as regurgitated acid, or vomit. Medications such as vitamin C and occupational and industrial exposure can also lead to dental erosion.

So are the two processes of dental caries and erosion interchangeable or does the similarity between these hard tissue lesions end at the involvement of acids?

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Dental Erosion - process by Mandana Donoghue is licensed under a Creative Commons Attribution-ShareAlike 4.0 International License.

The acids that cause erosion are very strong, with an average pH of 2 for the colas, 2-2.5 for citrus fruits and 1 for gastric contents and acid.  Repeated exposure, to acids with pH much lower than 5.4 (critical pH for demineralization)  leads to surface demineralization.  The soft surface is susceptible to loss by abrasion from food, or a toothbrush. The surface lesions are resistant to remineralization. Repeated cycles of acid exposure will lead to smooth, cupped out cavities. These lesions have smooth edges.  Surfaces most susceptible to erosion are the palatal surfaces of maxillary anterior teeth, although, other teeth are also affected.  

Dental caries process by Mandana Donoghue is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

The acid that leads to demineralization in dental caries is a  metabolic product of the acidogenic bacteria of the dental plaque or biofilm. Although the caries process is a multifactorial one and carbohydrate exposure is not by itself a determinant of caries development, repeated carbohydrate exposure tilts the scale towards caries.  The cariogenic bacteria in the plaque, metabolize dietary carbohydrates and release acids. The H⁺ ions released in the bacterial plaque act on the underlying tooth surfaces and lead to subsurface demineralization of the tooth. Dental plaque has a dual role in the caries process. The first is the provision of a suitable microenvironment for attachment and multiplication of the acidogenic bacteria that cause caries.  The second role is the barrier effect it provides to the movement of the calcium and phosphate ions released from the tooth into the saliva, thus making it possible for the minerals to demineralize the surface after the pH level rises above 5.4. Although an argument can also be made that plaque delays the neutralization of acids on the tooth surface by slowing the ingress of saliva. Each carbohydrate exposure produces a cycle of acid production and neutralization.  Repeated exposures eventually lead to a carious lesion. The cavitated lesion develops due to the eventual breakdown of the unsupported enamel. The cavity is not smooth in outline, and the base which is softened dentin does not appear polished as in the erosion cavity.