Understanding the Chemistry of Dental Erosion

Abstract

The mineral in our teeth is composed of a calcium-deficient carbonated hydroxyapatite (Ca10-xNax(PO4)6-y(CO3)z(OH)2-uFu). These substitutions in the mineral crystal lattice, especially carbonate, renders tooth mineral more acid soluble than hydroxyapatite. During erosion by acid and/or chelators, these agents interact with the surface of the mineral crystals, but only after they diffuse through the plaque, the pellicle, and the protein/lipid coating of the individual crystals themselves. The effect of direct attack by the hydrogen ion is to combine with the carbonate and/or phosphate releasing all of the ions from that region of the crystal surface leading to direct surface etching. Acids such as citric acid have a more complex interaction. In water they exist as a mixture of hydrogen ions, acid anions (e.g. citrate) and undissociated acid molecules, with the amounts of each determined by the acid dissociation constant (pKa) and the pH of the solution. Above the effect of the hydrogen ion, the citrate ion can complex with calcium also removing it from the crystal surface and/or from saliva. Values of the strength of acid (pKa) and for the anion-calcium interaction and the mechanisms of interaction with the tooth mineral on the surface and underneath are described in detail.

Effect of foods and drinks on primary tooth enamel after erosive challenge with hydrochloric acid

“…5 The proposed protocol to simulate an episode of gastro-oesophageal reflux was adapted from the in vitro model of Hove et al 19 HCl, used in intrinsic erosion models, 20 is a strong acid, 21 which, in the presence of water, dissociates completely into hydrogen ions and chloride ions, removing the mineral surface. 22 Short-term acid exposures cause surface changes observed before the loss of tooth structure. 23 Although there has been a standardisation of the methodology applied in the choice of substrate, size of specimens, polishing procedure, pre-treatment with artificial saliva, baseline microhardness measurements, and volume and duration of acid exposure, this study showed a significant difference across samples exposed to HCl, limiting the comparison of snacks within each time period.…”

“…Although it is a weak acid, citric acid chelates calcium from hydroxyapatite 18 and promotes the dissolution of crystals by binding the hydrogen ion to the carbonate and/or phosphate ion. 22 Although the manufacturer does not mention the presence of acidulants (e.g., citric acid) or any other acids, fermented milk (Yakult ® ) has a pH of 3.67 and may cause superficial mineral loss in bovine surface enamel after 20 min of exposure, interspersed with exposure to artificial saliva. 14 In this study, fermented milk did not exacerbate the mineral loss caused by endogenous simulation challenge at 28 days and by a total exposure of 56 minutes.…”

Dietary Habits and Oral Hygiene Practice amongst Dental Students at the College of Dentistry, Princess Nourah University

“…Both incidence and prevalence of dental erosion have increased considerably among children & young adults [4]- [6]. Lifestyles have changed through time with the high consumption of acidic food & carbonated beverages [7]. Dietary acids are one of the most commonly cited causes of erosion [8], and soft drink consumption has been associated with dental erosion [9].…”

Surface roughness of a resin composite

“…Indeed, a more acidic pH does not appear indicate greater erosive potential 26 . Erosion depends on the combined effect of physicochemical properties, total amount of acid, mineral content and titratable acidity [26][27] .…”