The effect of investment materials on the surface of cast fluorcanasite glasses and glass-ceramics.

Modified fluorcanasite glass-ceramics were produced by controlled two stage heat-treatment of as-cast glasses. Castability was determined using a spiral castability test and the lost-wax method. Specimens were cast into moulds formed from gypsum and phosphate bonded investments to observe their effect on the casting process, surface roughness, surface composition and biocompatibility. Both gypsum and phosphate bonded investments could be successfully used for the lost-wax casting of fluorcanasite glasses. Although the stoichiometric glass composition had the highest castability, all modified compositions showed good relative castability. X-ray diffraction showed similar bulk crystallisation for each glass, irrespective of the investment material. However, differences in surface crystallisation were detected when different investment materials were used. Gypsum bonded investment discs showed slightly improved in vitro biocompatibility than equivalent phosphate bonded investment discs under the conditions used.