Internal fit of pressed and computer-aided design/computer-aided manufacturing ceramic crowns made from digital and conventional impressions

Statement of problem. No studies have evaluated the internal adaptation of pressed and milled ceramic crowns made from digital impressions. Purpose. The purpose of this in vitro study was to evaluate the internal fit of pressed and milled ceramic crowns made from digital and conventional impressions. Material and methods. Thirty polyvinyl siloxane (PVS) impressions and 30 Lava COS impressions made of a prepared dentoform tooth (master die) were fabricated. Thirty crowns were pressed in lithium disilicate (IPS e.max Press), and 30 crowns were milled from lithium disilicate blocks (IPS e.max CAD) (15/impression technique) with the E4D scanner and milling engine. The master die and the intaglio of the crowns were digitized with a 3-dimensional laser coordinate measurement machine. The digital master die and intaglio of each crown were merged. The distance between the die and the intaglio surface of the crown was measured at 3 standardized points. One-way ANOVA was used for statistical analysis (alpha=.05). Results. One-way ANOVA revealed that the internal gap obtained from the Lava/press group (0.211 mm, +/- SD 0.041) was significantly greater than that obtained from the other groups (P<.001), while no significant differences were found among PVS/press (0.111 mm +/- SD 0.047), PVS/CAD/CAM (0.116 mm +/- SD 0.02), and Lava/CAD/CAM (0.145 mm +/- SD 0.024). Conclusions. The combination of the digital impression and pressed crown produced the least accurate internal fit.