Crystallization and colour of apatite - Leucite glass-ceramics

Needle-like fluorapatite and leucite containing glass-ceramic was prepared in a glass from the system SiO2 - Al2O3 - Na2O - K2O - CaO - P2O5 - CeO2 - F- using high heating rates and crystallization temperatures between 700 - 1150 degreesC for dental restoration. Phase separation followed by both vol ume and surface crystallization of apatite and leucite respectively [1] wer e found after a two-step heat treatment of the powdered glass samples. Crys tallization is demonstrated by X-ray diffraction patterns and electron micr ographs. CIELAB colour differences (DeltaE*(ab)) and CIE 1976 lightness dif ferences (DeltaL*) [4] were calculated utilizing rectangular coordinates (L *, a*, b*) measured by tristimulus colorimeter in function of heat treating temperature. Results indicate that both colour and lightness differences d ecrease down to a scarcely shade of difference in temperature range of 1000 degreesC - 1150 degreesC.