Surface quality of gypsums when poured against alginates.

Alginate impression materials are universally accepted for the fabrication of dental casts. Since casts reflect a direct link between the patient and the dentist, it is imperative that their surfaces be of highest quality. This study assesses the quality of dental cast surfaces when poured against alginate impression materials. A standardized system previously designed by the authors allowed the evaluations of 16 different gypsums poured against 32 different alginate surfaces, including a plexiglass control surface. Five hundred and twelve gypsum surfaces were produced and evaluated for quality in the following manner: 1) assessed visually with the aid of photomicrographs for surface smoothness; 2) evaluated by a modified Vickers scratch test for surface hardness. The results indicate that certain gypsum-alginate combinations provide superior surfaces with respect to hardness and smoothness, while other combinations suggest a high degree of incompatibility.