Preparation of a Calcium Titanium Phosphate Glass-Ceramic with Improved Chemical Durability

A calcium titanium phosphate glass-ceramic for use as a dental material with excellent chemical durability was derived from a mother glass with a small amount of fluorine. The laser Raman spectroscopic analysis showed that 35CaO-10CaF(2)-30P(2)O(5)-25TiO(2) glass, as the nominal composition, consists of ortho-, pyro-, and meta-phosphate groups. On heating the glass at 865 degrees C, orthophosphate crystals, such as fluorine-containing oxyapatite (Ca(10)(PO(4))(6)(O,F(2))) and the Nasicon-type phase (CaTi(4)(PO(4))(6)), were preferentially precipitated; the apatite particles of several tens of nanometers in size were embedded in the CaTi(4)(PO(4))(6) phase. The pale bluish color of the glass-ceramic indicated that titanium ions were included in the residual glassy phase. When the glass-ceramic was treated with dilute hydrochloric acid, only the apatite particles at the surface were leached out, while no CaTi(4)(PO(4))(6) phase was etched; the dissolution of the glass-ceramic was effectively controlled. Almost no dissolution of ions from the glass-ceramic occurred in water. It was suggested that the behavior is a result of the microstructure of the glass-ceramic, which consists of crystalline and glassy phases with excellent chemical durability.