Erosion-Driven Enamel Crystallite Growth Phenomenon at the Tooth Surface In Vitro

Abstract

The erosion of tooth enamel is a common oral disease. The erosion pattern and location and the effects of nanoscale chemical composition on the erosion susceptibility of enamel have been well documented. However, the enamel remineralization accompanied by erosion and its underlying physicochemical mechanisms still remain poorly understood. Here, using rat molars selected for its good relevancy to human teeth, we investigated the remineralization behavior of the outermost enamel surface at the nanoscale level during erosion in diluted hydrochloric acid solutions. While particles on the outermost enamel surface that represent the termination of crystallites protruding to the surface from the near-surface core eroded by acid-attack, the lateral-growth of the particles (i.e., the main remineralization picture of the surface enamel) occurred concurrently. Ionic analyses indicate that the particle growth is driven by the local increase in pH near the eroding enamel surface as a result of the combination of the PO4 3– and CO3 2– released from the enamel surface with H+. As the pH increases eventually to the equilibrium pH level (∼5.5), a local supersaturation of solute ions is induced, resulting in particle growth. A simple growth model based on the experimental results together with an assumption that the particle growth is a diffusional process suggests that the particle growth rate is controlled by the degree of supersaturation and accommodation site for solute ions, which are affected by the pH of solution eroding the enamel surface. The remineralization mechanism presented by our study can explain how the enamel on being acid-exposed or tooth decay progress by beverage or food can naturally remineralize in the oral cavity and how remineralization can foster different surface topology at the nanoscale, depending on the pH value of etchant before the dental filling material is applied.

Amelogenin-inspired peptide, calcium phosphate solution, fluoride and their synergistic effect on enamel biomimetic remineralization: an in vitro pH-cycling model

“…A supersaturated calcium phosphate remineralizing solution was used in the current study to be tested alone and in conjugation with the peptide. It was produced with an initial molar ratio of Ca 2+ to PO 4 3- ions equals 1.67 with a relatively high supersaturation degree that would thermodynamically accelerate the nucleation of crystals by precipitating numerous Ca-P clusters [ 11 , 42 ]. It was interesting to investigate the ability of fluoride to enhance and augment the remineralizing potential of the peptide and the remineralizing solution and to evaluate the mineral layer developed using such a combination.…”