The presentstudy, reports the chemicalcomposition of hypoplastic primary teeth examined by electron probe microanalyzer comparing with the normal partin the sametooth; andreports the X-raydiffraction results of the hypoplastic dental enamel and the normal dental enamel, and comparing the crystalline structure between the two dental enamel together with that of the synthetic hydroxyapatite. The aim of this study was to find out any change of crystalline structure. Two exfoliated hypoplastic deciduous anterior teeth were used for the electron probe study. Each tooth was sliced into two parts along the defect lesion border in a labio-lingual direction. The normal part was used as control. Determinations of weight percentage (wt%) per mass volume were made in continuous scan for P,Al, Mg, Ca, Mn, Fe, Zn, Sr, Na, K and F, from the enamel edge of hypoplastic bottom to dentin-enamel junction. Four exfoliated hypoplastic deciduous anterior teeth and eight exfoliated normal deciduous anterior teeth were used for the X-ray diffraction study. We found by X-ray diffraction that the length of the a-axis of enamel crystallite and the d-spacing (corresponding 300) were increased in the defective enamel. These could be associated with the increased content of magnesium detected by electron probe. The presentstudydemonstrated thattherewereboth quantity and qualitychanges in the enamel hypoplasia lesion, which may increase the susceptibility of the defective teeth to caries.

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