Spectroscopic analysis was used to study the patterns of changes in the mineral and matrix properties of dentin during maturation of the tissue. Fourier Transform Infrared Imaging (FTIRI) analyses on undecalcified semi-thin sections from fetal bovine incisors and developing mouse molars were performed. In addition, fetal bovine microdissected mantle and circumpulpal dentin specimens of successive tissue age were analyzed by Fourier Transform Infrared (FTIR) analysis and by amino acid and matrix phosphate assays.
In the initial studies, the formation of mantle and circumpulpal dentin as two distinct dentin compartments in the developing fetal incisors was established through analysis of distribution of mineral:matrix and mineral crystallinity values. Changes in the mineral:matrix, mineral crystallinity, acidic phosphate substitution and carbonate substitution in the mineral of mantle and circumpulpal dentin during maturation were subsequently quantitatively analyzed from FTIRI results. In this study, separate patterns of changes in mineral properties were found for mantle and circumpulpal dentin, in terms of initial and final levels and rates of increase or decrease of mineral properties values. Spectroscopic analysis of different maturation stages microdissected mantle and circumpulpal dentin specimens showed a great decrease in the dentin relative water content, affecting the dentin matrix conformation.
Chemical analyses of similar microdissected specimens showed a significant increase in the organic phosphate of dentin matrix occurring during maturation. This increase was associated with continuing phosphorylation of existing phosphoproteins without further changes in the protein density. Finally, the study of dentin maturation using 6 day-old mouse molars by FTIRI was validated. Reproducibility in the pattern of changes in the mineral properties examined was found to be highly dependent on the sectioning orienation of molars. It is likely that higher resolution analytical methods and/or slightly older animal age would enhance the analytical outcome in such studies.
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