Objectives: The purpose of this study was to evaluate the dimensional behavior of working casts for the construction of implant-supported prostheses, using as pouring materials type IV dental stone (group 1), type V dental stone (group 2), resin-reinforced stone (group 3) and polyurethane resin (group 4). A master cast and specific metal trays were developed to obtain these casts.
Methods: Three implants were positioned parallel and in a triangular arrangement in the metal base. Using locating posts at the base, 40 condensation silicone impressions were performed with the use of the trays. For each pouring material, 10 casts were obtained and the distances AB, BC, and AC (distances through the center of the implants) were measured using a coordinate measuring machine (CNC, 550 AMC Model, Zeiss, Germany).
Results: The polyurethane resin casts showed contraction and their inter-implant distances were smaller in AB (-0.72%) and AC (-0.49%). The casts fabricated with type V dental stone presented a statistically significant expansion in distances AB (0.002%) and AC (0.29%). The dimensional behavior of type IV dental stone was one of contraction on AB and AC measures, -0.232% and -0.022%, respectively. Resin reinforced stone presented contraction on the AB measure (-0.24%) and expansion on AC (0.022%).
Conclusions: The data for BC distances in groups 1, 2, 3, and 4 were not statistically significant. When compared to the master cast, groups 1 and 3 presented the best results regarding dimensional stability, showing to be statistically equivalent to the master cast, followed by group 2 and group 4 which exhibited statistically significant differences under the form of expansion (group 2) and contraction (group 4).