A study of the surface hardness and dimensional stability of several intermaxillary registration materials.

This study compared the surface hardness, the effect of time on surface hardness, and the dimensional stability of various intermaxillary relationship registration materials. The Shore hardness values of one zinc oxide-eugenol material, one polyether, and seven poly(vinyl siloxane) materials were obtained at 30 minutes and 24 hours after the start of mixing. The dimensional stability of one polyether and seven poly(vinyl siloxane) materials was measured using a standard mold as described in American Dental Association (ADA) Specification No. 19. All materials exhibited relatively high surface hardness despite some statistical differences among them. Four materials possessed higher surface hardness at 24 hours than at 30 minutes. Although the polyether showed significantly lower dimensional stability than the other materials, all materials satisfied the minimum requirement for Type I elastomeric impression material.