Comparison of the fit of Procera crowns made from stone with those made from polyurethane resin

This study compared the average marginal gap of Procera crowns fabricated from a definitive cast made from polyurethane resin with those made from type IV stone. A metallic maxillary central incisor and first premolar were prepared according to the Procera guidelines and incorporated into a U-shaped definitive cast. From this definitive cast, 20 primary casts were made in polyurethane resin. Two sets of impressions (10 with type IV stone and 10 with polyurethane resin) were made and poured onto these casts. Forty pure aluminum oxide substructures for Procera crowns were made for these groups, with 10 incisors and 10 premolars in each group. Each substructure was cemented on the respective primary die and sectioned. Using an optical microscope and special software, sections were measured and compared for marginal adaptation. Based on the findings, both materials were equally adequate for producing a Procera crown. However, the mean margin gap was consistently larger for type IV stone dies than for polyurethane resin dies.