Pathogenesis
Acids with pH below the critical threshold (5.5 for enamel, 6.0-6.7 for dentin) dissolve calcium and phosphate ions from the tooth surface through a direct chemical process — no bacteria required.
Chelating acids (citric, malic, oxalic) are particularly damaging because they both lower pH and chelate calcium ions, keeping the acid in contact with the tooth and preventing remineralization.
Erosion begins with softening of the outermost enamel layer, which is then removed by mechanical forces — toothbrushing, tongue action, occlusal forces. This is why dentists advise not to brush immediately after acid exposure.
Saliva is the primary protective mechanism: it dilutes and clears acids, buffers pH (bicarbonate system), and provides calcium and phosphate for remineralization. Reduced salivary flow (medication side effects, Sjögren's syndrome) dramatically increases erosion risk.
Peristaltic motion of the esophagus normally prevents reflux; in GERD, the lower esophageal sphincter is deficient, allowing gastric acid to reach the oral cavity repeatedly during the day and especially at night.