J.M.P.M. Borggreven

Biological calcium phosphates and their role in the physiology of bone and dental tissues I. Composition and solubility of calcium phosphates

SummaryVariations in the composition of bone and tooth mineral are consistent with the model that the constituents are a mixed microcrystalline apatite (AP)-octocalcium phosphate (OCP) like phase and an amorphous or submicrocrystalline calcium phosphate (ACP) like phase whereby these phases can occur in different proportions. An appropriate model for a description of the variable composition and the solubility behavior of the apatite phase is given by the formulan

Solubility behaviour of whole human enamel.

begin{array}{*{20}c} {begin{array}{*{20}c} {Ca_{5 - x - y - u} Na_{frac{2}{3} y} } {{ (PO_4 )_{3 - x - y } (CO)_{x + y} } (H_2 O)_{y + z} OH_{1 - x - frac{1}{3} y - 2u} } end{array}} end{array}

Posteruptive Maturation of Tooth Enamel Studied with the Electron Microprobe

n in which the compositional parameters x, y, z, and u each account for one type of defect mechanism. Other point defects are formed as well by incorporation of minority amounts of ions such as Cl−, K+, and F−; a number of trace elements can substitute for Ca2+ ions under in vivo conditions. It is suggested that the incorporation of ions in or loss from the crystals in contact with aqueous solutions is reversible. Literature data are used to show the direction in which the solubility product of the apatite phase shifts by incorporation of the different physiologically relevant ions. A quantitative evaluation of the available literature data revealed that Na+ and CO3= incorporation is the main cause for shifts in the solubility product of biological apatites.

Influence of Fluoride on in vitro Remineralization of Artificial Subsurface Lesions Determined with a Sandwich Technique

In this study a mathematical model for the caries process is presented. It includes diffusion of ions, dissolution of mineral and complexation of ions. The conclusions from experiments with the model

Variations in the mineral composition of human enamel on the level of cross-striations and striae of Retzius

The rate of dissolution of whole human enamel was studied by carrying out artificial caries experiments in buffers of known pH and known degree of undersaturation with respect to hydroxyapatite and by

Acid-susceptibility of Lesions in Bovine Enamel after Remineralization at Different pH Values and in the Presence of Different Fluoride Concentrations

Extensive ‘white spot’ and ‘brown/white spot’ lesions with intact surfaces in 11 molars were investigated by microradiography and electron microprobe analysis for Fe, Ca, Na and Cl. At the surface of the brown spots some Fe was found. Within the lesions a preferential dissolution of Na and a slight enrichment of Cl was found. This suggests that Na and Cl are sited in different parts of the mineral and the Na-containing part appears to be more soluble. The Na and Cl contents of a lamination approach those of adjacent sound enamel. This indicates that laminations do not result from major reprecipitation of a less soluble calcium phosphate within the formed lesion, but that the mineral is protected from local dissolution early in the process. A possible mechanism is discussed.

Electron Microprobe Analysis and Microradiography of Some Artificial Laminated Carious Lesions

Third molars just erupting and premolars (before eruption or half a year or 3.5 years after eruption) were extracted and sawn vertically through the buccolingual plane. Tracings of the Ca, P, Na and M

MICRORADIOGRAPHY AND ELECTRON-MICROPROBE ANALYSIS OF SOME CARIES-LIKE LESIONS OF ENAMEL PREPARED IN VITRO IN HUMAN TEETH

Remineralization experiments of bovine enamel with subsurface lesions were carried out with the use of a sandwich technique. The remineralizing solutions contained no or 2 ppm fluoride added to the solution. The amount of remineralization was determined after remineralization periods up to 324 by means of quantitative microradiography. After 84 h the group with fluoride showed significantly (p less than 0.05) less remineralization than the nonfluoride group. This inhibition of fluoride on the remineralization may be explained by the inhibiting effect that fluoride at certain concentrations has on the crystal growth of apatites.