There are varying opinions on the primary cause of cupping/cratering on the incisal edges of anterior teeth and cusp tips of posterior teeth. It is a common belief that only acid causes the cupping or cratering of the exposed dentin surrounded by a rim of enamel. This may not be the case. 


The Effect of Acid Insult on Exposed Dentin

In my research, I highlighted the most interesting thoughts about this topic:

  • Damm stated the ease of exposed dentin dissolution, combined with the acid resistance of enamel, creates the diagnostic pattern of erosion associated tooth wear, in which cup-like depressions of dentin are surrounded by elevated rims of enamel.1  


  • Grippo demonstrated the susceptibility of enamel and the resistance of dentin to acid challenge.2 After 96 hours of citric acid immersion, the tooth structure of his specimens showed affected enamel (acid demineralized) and unaffected dentin. 


  • Dzakovich states that the term biocorrosion should be expurgated from dental nomenclature. He explains that corrosion is an oxidation reduction reaction that occurs by the breaking of covalent bonds. Oxidation of calcium hydroxyapatite is a nonmetallic ionic crystal with ionic bonds, not covalent bonds. Calcium hydroxyapatite is susceptible to erosion (chemical insult) and abrasion (loss of tooth structure due to the application of exogenous compounds such as dentifrices). The combination of dentifrice and toothbrush, not the toothbrush alone, causes the loss of tooth structure. Attrition is the wearing away of tooth structure resulting from friction of an opposing tooth rubbing against it.


  • In Dzakovich's study3, 68 extracted human teeth were used for evaluation, and enamel was reduced to expose the dentin. The variables included were different teeth, position, occlusal reduction of enamel to expose varying amounts of dentin, brushing media, two different abrasiveness levels of dentifrice (low -33.9 and high-139.5 RDA) and water only, and the duration of acid challenge. The time of horizontal brushing (soft bristles)—150,00 strokes—simulated 10-15 years.
Incisal cupping/cratering.
Figure 1: Incisal cupping/cratering.

The In Vitro Study

The following conclusions were also found in Dzakovich's in vitro study:

  1. There was no loss of dentin or enamel when brushing with water only (nonabrasive)
  2. The greater the dentifrice’s RDA, the greater the cupping/cratering within exposed dentin of nonacid-challenged teeth.
  3. Acid challenge accelerated the loss of both enamel and the mineralized component of peritubular dentin, regardless of the cleaning medium.
  4. Acid challenge alone did not affect mantle dentin.
  5. A longer acid challenge resulted in greater demineralization and wear of the inorganic components of enamel and peritubular dentin and thus shallower-appearing cupping/cratering.
  6. Contrary to many published opinions, acid challenge alone did not result in cupping/cratering of incisal/occlusal surfaces of teeth.


When looking at the effects in vivo, you need to consider other sources of abrasion such as the tongue and the mastication of food that may affect your treatment plan. According to the research cited here, it’s not just acid coming in contact with the teeth that causes cupping or cratering of exposed dentin.

Robert Winter, D.D.S., is a member of Spear Resident Faculty.



  1. Damm D. (2007) Cup-like depressions of dentin. Academy of General Dentistry, 55:479-484
  2. Grippo, J. O. (1991). Abfractions: a new classification of hard tissue lesions of teeth. Journal of Esthetic and Restorative Dentistry3(1), 14-19.
  3. Dzakovich, J. J., & Oslak, R. R. (2017). In vitro effects of acid challenge on incisal/occlusal cupping/cratering. The Journal of Prosthetic Dentistry, 117(1), 124-131.