Variables Affecting the Accuracy of Implant Master Casts: An In Vitro Pilot Study

Impression and master cast accuracy have been identified as being the major determinants of superstructure fit in implant-supported restorations. The goal of this in vitro investigation was to determine the effects of different transfer components, impression materials, disinfection, storage time, and stone type on master cast accuracy. Following impression making from a reference model with two internal-hex bone-level implants and master cast fabrication (eight experimental groups; n = 5), a bar-type measurement device equipped with a strain gauge was fixed on all master casts while strain development was recorded. Statistical analysis was performed applying ANOVA and paired t-tests with the level of significance set at α = 0.05. The transfer components with plastic sleeves caused maximum misfit strain which was significantly greater as compared to click (P = 0.02) and open tray transfer components (P = 0.00). No significant effect on master cast accuracy was recorded for the parameters impression material, impression disinfection, and storage of impressions or casts. Lower strain development was observed in casts poured in type 3 stone as compared to casts poured in type 4 stone (P = 0.01). For the bone-level implant system considered here, the great levels of accuracy could be achieved using pick-up impressions with either click or open tray impression components.