HIGH-STRENGTH DENTAL GYPSUM PREPARED BY COLD ISOSTATIC PRESSING

Powder of a dental plaster (Moldabaster(R), Bayer) was compacted by co ld isostatic pressing (CIP) at 300 MPa for 10 min and immersed in wate r for 1 h. The compressive strength of the CIP-processed material was compared with that of conventionally processed material. The green blo ck of plaster before water immersion was carvable with a green density and green strength of 50% and 5 MPa, respectively. The compressive st rength of the CIP-processed gypsum after 24 h was three times higher t han that of conventionally processed, 103 compared with 29 MPa, and th e microhardness (Vickers hardness number, VHN) of CIP-processed materi als was 40 compared with 12VHN. An increase of density was also record ed. It seems that the CIP process produced a dense and pore-free gypsu m with a composite-like structure. The high-strength gypsum processed by CIP may extend the applications of this material in the medical fie ld as implant materials.