Digital evaluation of marginal and internal fit of single-crown fixed dental prostheses

The present study used a new, digitized version of the impression replica technique, namely the dual-scan technique, to evaluate the adaptation of single-crown fixed dental prostheses (FDPs). Scans of the bare master model and of the master model with a silicone layer representing the cement layer were superimposed and analyzed using designated software. Single crowns produced using the lost-wax metal casting technique were included. The cement space of the band width, 0.5-1.0 mm from the preparation margin (marginal fit), was smallest for crowns made from laser-sintered cobalt-chromium. The internal fit in both mesial-distal and buccal-palatal directions was statistically significantly better for crowns made using the conventional lost-wax metal casting technique than for crowns produced using computer-aided design/computer-aided manufacturing (CAD/CAM). Fixed dental prostheses produced by milled cobalt-chromium had the loosest internal fit. The results agree with those of our previous study of the same test specimens, in which the triple-scan method was used, and imply that the dual-scan method is well suited for adaptation studies.