[Influence of acid buffer on the crystallinity of enamel apatite]

Abstract

The affects of acetic buffers on the crystallinity of an enamel apatite were examined in the present study. Dual aspects, crystallite size and lattice imperfection related to the crystallinity were analyzed by the process of Variance and Fourier analysis based on the X-ray diffraction line profiles. For this purpose both enamel apatite and synthetic hydroxyapatite were analyzed through acetic acid buffer decalcification, and comparison was made. In addition to the analysis, morphological change of the apatite after acid decalcification was observed by a transmission electron microscope (TEM). The results obtained in the present study were as follows: 1) Wedge-shaped defects formed on a prism plane were observed. In the further stage, wedge-shaped defects were also formed on a basal plane, and it proceeded into the center of the crystallite and consequentry slit similar to defected image was observed. 2) Lattice imperfection of the enamel and synthetic apatite were noticed both on the c-axis and a-axis. Among the factors which contributed to the variance, the "mistake" of lattice was much more likely than the crystallite size, and more mistakes in the direction of the a-axis rather than the c-axis was noticed. 3) A diminished crystallites size was found after acid treatment and diminishing on the c-axis was more apparent than the a-axis. 4) The crystallinity of the apatite was improved through acid treatment, and this improvement was attributed to a diminishing of mistakes. 5) Diminishing of mistakes through acid treatment was detected apparently along the c-axis. According to the results obtained in the present study, crystallite of enamel apatite showed decrease in size, although crystallinity through acid treatment was improved due to the diminishing of mistakes along the c-axis. This may be explained as following in that when apatite crystals were acid treated, the loci of lattice dislocation was selectively dissolved and consequently the more stable crystallite was left.