CHEMICAL CHARACTERIZATION OF IN-VIVO AGED ZINC PHOSPHATE DENTAL CEMENTS

The chemical composition of zinc phosphate dental cements aged in vivo was studied. Twenty-seven samples aged 2 to 43 years were investigate d using X-ray diffraction, infrared spectroscopy, P-31 nuclear magneti c resonance spectroscopy, thermogravimetric analysis and differential scanning calorimetry. Evidence for the presence of zinc oxide, amorpho us zinc phosphate, water of hydration and crystalline zinc phosphate t etrahydrate was found. The latter was identified as hopeite; it was pr esent in 92% of the cements studied. No correlation with time concerni ng either the chemical structure of the components or their relative a mounts was found. Zinc phosphate dental cements show very good chemica l stability on long-term use.