Influence of tissue conditioners upon the surface hardness of dental stone and improved dental stone.

The surface hardness of dental stone and improved dental stone was investigated when crystallised in contact with tissue conditioners and compared with that observed when the two types of gypsum are crystallised in contact with impression materials used clinically. Vickers hardness tests were performed 45 minutes, 2 hours and 24 hours after the beginning of stone mixing. The tissue conditioners did not have adverse effects on the surface hardness of gypsum products. On the contrary, they gave casts with excellent surface hardness, as did the elastomeric impression materials.