A9 Dental Erosion (non-bacterial)

Topic

Non-bacterial dental erosion is the progressive loss of hard dental tissue caused by acids, a process in which bacteria play no part. These acids can be extrinsic—such as those derived from an acidic diet, soft drinks, citrus fruits, or repeated vomiting associated with bulimia—or intrinsic, such as gastric acid reaching the mouth during gastroesophageal reflux.

Unlike dental caries, where biofilm bacteria produce acids that first attack the subsurface of the tooth enamel, non-bacterial dental erosion directly attacks the enamel surface without passing through a subsurface stage; furthermore, biofilm never mediates the contact between the acid and the enamel.

The aggressiveness of an erosive acid depends on three of its inherent characteristics: the lower the pH of the erosive agent, the greater its capacity to dissolve tooth enamel; the higher the acid's buffering capacity, the more acid remains active after dilution with saliva and the longer its erosive effect persists; and the higher the concentration of calcium and phosphate already dissolved in the acid, the lower its capacity to continue dissolving enamel, as the acid approaches its own saturation limit.

Beyond the chemical aggressiveness of the acid, the rate of erosion also depends on the actual duration of contact between the erosive acid and the tooth enamel: the more frequent and prolonged the exposure to the erosive acid, the higher the resulting rate of erosion. Salivary flow acts in the opposite way by diluting and neutralizing the erosive acid and clearing it from the enamel surface; the greater the salivary flow, the lower the final rate of erosion. The dissolution of dental enamel caused by these erosive acids does not proceed in a simply proportional manner; rather, it is highly sensitive to how far the saliva-acid solution is from its saturation point relative to the enamel mineral. The further the solution is from saturation, the faster the enamel dissolves, and even minor changes in the degree of saturation can lead to disproportionate changes in the rate of dissolution.

When erosion progresses in isolation—unaccompanied by other wear mechanisms—it leaves the enamel surface shiny, smooth, and cupped; this contrasts sharply with the matte, scratched surface characteristic of abrasive wear. This difference in surface appearance allows clinicians to distinguish pure erosion from friction-induced wear, such as that caused by bruxism.

The severity of this hard-tissue loss is clinically quantified using an index that classifies each sextant of the mouth on a four-level scale, ranging from the absence of erosion to the most severe loss of enamel and dentin. This index encapsulates—in a single figure per sextant—the cumulative outcome of the erosive acid's aggressiveness, the duration of exposure, and the protective effect of salivary flow; it thus completes the characterization of non-bacterial dental erosion as a progressive loss of hard dental tissue occurring independently of bacterial activity.

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