Enamel Demineralization in Primary and Permanent Teeth

Abstract

Although enamel demineralization is important for our understanding of caries formation, no consensus has been reached regarding the possible differences in susceptibility of primary and permanent enamel. We used the constant composition (CC) technique to investigate the acid-induced demineralization of these tissues at a relative undersaturation with respect to hydroxyapatite (HAP) of 0.902, pH = 4.5, and ionic strength = 0.15 mol L −1 . The demineralization rates showed significant differences, primary enamel having the greater susceptibility to dissolution during an initial linear stage: 1.5 ± 0.5 × 10 −10 mol mm −2 min −1 compared with 2.6 ± 0.5 × 10 −11 mol mm −2 min −1 for permanent enamel. During the reactions, we observed nanosized crystallites which attached to the enamel surfaces or escaped into the bulk solution. These nanosized crystallites were kinetically protected against further dissolution, even though the solutions remained undersaturated. It is hypothesized that they may contribute to the remarkable mechanical and dynamic characteristics of enamel.

Nanosized particles in bone and dissolution insensitivity of bone mineral

“…Residues of these nanoparticles at the end of dissolution reactions or preexisting nanoparticles that are stabilized due to the lack of surface defects/pits are able to resist dissolution. The phenomena of dissolution termination and "critical" pit size are not arbitrary; rather, these self-tuned and dissolutioninsensitive effects for tiny crystallites and biomaterials such as tooth enamel 21,22 occur specifically at the nanoscale. In addition, since traditional solution theories are based on experiments involving soluble salts, these phenomena are not observed since the critical conditions would be outside the range of the experimental techniques employed.…”

Dynamics of crystallization and dissolution of calcium orthophosphates at the near-molecular level

“…The effects become more important as the particle size approaches the critical length because more of the surface is likely to be composed of steps shorter than the critical length. This new dissolution model incorporating particle size considerations [38,39] can explain bulk demineralization of sparingly soluble salts such as HAP [40][41][42][43][44], which is generally initiated and accompanied by the formation and development of pits on the crystal surfaces; the dissolution rates are also determined by the pit densities and spreading velocities. The rate of step movement from a pit of radius r can be obtained from:…”

Effect of Fluoride on the Morphology of Calcium Phosphate Crystals Grown on Acid-Etched Human Enamel

“…The pH of the calcification solution was adjusted with 1 M HCl to 7.60 using a 718 STAT Titrino (Metrohm, Herisau, Switzerland). The relative supersaturation values ( ) were calculated by the SPEC96 speciation program with the Davies extension of the Debye-Hückel equation, using mass balance expressions for total calcium and total phosphate with appropriate equilibrium constants as previously described [Wang et al, 2006]. Fluoride, from NaF ( 1 99%, Sigma-Aldrich, St. Louis, Mo., USA), was added to obtain the final desired concentrations of fluoride just before immersing the tooth slice.…”