Our long-term strategy for understanding normal and pathological enamel mineralization is to determine: a) the driving force for precipitation of calcium phosphate salts during amelogenesis, b) the cellular role in establishing such a driving force, and c) the possible regulatory mechanism(s) of amelogenesis related to the matrix-mineral interaction. The information obtained will be applied to the study of pathological amelogenesis using animal models (minipigs and rats) under various fluoride regimes. The present proposal includes the following specific aspects: 1) Separation of the fluid phase from the secretory enamel of a single animal (minipig), determination of its ionic composition, and changes in it induced by pathological agents (fluoride). Analyses of micro volumes of the fluid will be conducted by the use of ion chromatography and micro- electrodes. 2) Identification of the calcium-binding ligands in the fluid. The protein constituents in the fluid will be separated by microdialysis, electrophoresis, and chromatography. The calcium-binding properties of the separated fluid constituents will be determined through the use of ion- specific electrodes, 45Ca autoradiography, and flow-rate dialysis. Based on the foregoing results, we will re-evaluate the degree of saturation of enamel fluid with respect to enamel and other calcium phosphates of interest. 3) Investigation of the properties of amelogenins and enamelins of porcine and murine models, and their degradation in situ. The properties concerned are: a) their selective adsorption onto apatitic surfaces, b) their solubility in physiologic aqueous solutions, and c) their hydrophobic/hydrophilic nature. 4) The mechanism of adsorption of the secreted amelogenin onto apatitic surfaces. The selective adsorption of the amelogenin will be related to the presence of specific segments at the N- and C-terminals, both of which have a high homology in the matrix proteins of mammal enamel. Efforts will also be made to ascertain the effect of segments on the molecular conformation in solutions and on solid surfaces. 5) Investigation of the functional aspects of the matrix-mineral interaction in enamel mineralization. Interest will be focused on the effects of protein coatings of apatite crystals on (a) the incorporation of ions (calcium, phosphate, and fluoride) from solutions onto the crystal surfaces, (b) kinetics of precipitation in fluid-like environments, and (c) the aggregation and morphology of growing crystals.
Showing the most recent 10 out of 22 publications
