Evaluation of implant-supported connecting crowns fabricated by optical and conventional impression methods

Purpose To investigate the accuracy of implant-supported connecting crowns fabricated with digital definitive casts and conventional definitive casts.Methods Using a master model with two implant bodies inserted into the right mandibular molar area, 10 digital definitive casts were fabricated. Additionally, 10 conventional definitive casts were fabricated. The distance and angle between the two abutments of each definitive cast were compared. To compare the amount of lift of the incisal pin, each of the 10 superstructures was fabricated via computer-aided design/computer-aided manufacturing and then returned to the master model.Results No significant difference was observed for either the angle or the distance between the two abutments. The amount of lift of the incisal pin when the superstructure obtained via the optical method was returned to the master model was significantly larger than that when the superstructure obtained via the conventional method was returned to the definitive cast and the master model. No significant difference was observed after occlusal adjustment of the superstructures obtained using the conventional method.Conclusions The precision of definitive casts obtained via the optical method was virtually equal to that of definitive casts obtained via the conventional method. The accuracy of implant-supported connecting crowns fabricated using the optical method was significantly lower than that of implant-supported connecting crowns fabricated using the conventional method. This is attributed to the alignment of the maxillary and mandibular digital definitive casts.