The Influence of Material and Veneering on Fit of CAD-CAM-crowns

Objectives: To evaluate in vitro the marginal fit of CAD-CAM crowns made from Lithium Disilicate (IPS e.max CAD, Ivoclar Vivadent) and Zirconia (Zenostar, Ivoclar Vivadent) materials as a function of the veneering technique.
Methods: One ideally prepared model tooth #46 was duplicated into 64 identical plaster models. From the model a standardized wax pattern for a monoliothic crown and a coping were produced and used to mill 16 Lithium Disilicate monolithic crowns and 16 cores with CEREC. In an analog process using a 3-shape 810 scanner and Zenotec Mini Milling machine (Wieland USA) 16 Zirconia crowns and cores were fabricated. A factorial design with “material” (Lithium Disilicate [ECAD] or Zirconia [ZEN]); “design” (Monolithic, [M] or “core” [C]); and “finish” (as produced [AP]or veneered/glazed [VG]) was used to create the following groups: ZEN-M-AP, ZEN-M-V, ZEN-C-AP, ZEN-C-VG, ECAD-M-AP, ECAD-M-VG, ECAD-C-AP, ECAD-C-VG (n=8) and the milled objects were treated accordingly using ZirLiner, IPS e.max Ceram, and IPS e.max Glaze (Ivoclar Vivadent). The restorations were cemented to their dyes using stained Multilink Automix (Ivoclar Vivadent) and adhesive techniques, embedded into epoxy resin and sectioned into two planes with a diamond saw (Isomet 1000, Buhler). Using a Keyence VX-1000 digital microscope the vertical and horizontal fit at the finishing line was measured in a standardized way at 4 locations (mesial, distal, facial, oral).
Results: ANOVA (SAS 9.4) showed no differences between all ZEN groups; however, they had significantly higher horizontal gaps (116 µm) than ECAD groups (50 – 84 µm). For ECAD veneering significantly decreased the horizontal gaps to approximately 50 µm.
Conclusions: ZEN was not affected by the experimental parameters, but was less accurate. The fit of ECAD was better, but influenced by experimental parameters. Veneering and/or glazing of ECAD improved the fit significantly.
The authors thank Ivoclar Vivadent for supplying the materials and milling the restorations.