Marginal and internal fits of fixed dental prostheses zirconia retainers

Objectives. CAM (computer-aided manufacturing) and CAD (computer-aided design)/CAM systems facilitate the use of zirconia substructure materials for all-ceramic fixed partial dentures. This in vitro study compared the precision of fit of frameworks milled from semisintered zirconia blocks that were designed and machined with two CAD/CAM and one CAM system. Methods. Three-unit posterior fixed dental prostheses (FDP) (n = 10) were fabricated for standardized dies by: a milling center CAD/CAM system (Etkon), a laboratory CAD/CAM system (Cerec InLab), and a laboratory CAM system (Cercon). After adaptation by a dental technician, the FDP were cemented on definitive dies, embedded and sectioned. The marginal and internal fits were measured under an optical microscope at 50x magnification. A one-way analysis of variance (ANOVA) was used to compare data (alpha = 0.05). Results. The mean (S.D.) for the marginal fit and internal fit adaptation were: 29.1 mu m (14.0) and 62.7 mu m (18.9) for the milling center system, 56.6 mu m (19.6) and 73.5 mu m (20.6) for the laboratory CAD/CAM system, and 81.4 mu m (20.3) and 119.2 mu m (37.5) for the laboratory CAM system. One-way ANOVA showed significant differences between systems for marginal fit (P < 0.001) and internal fit (P < 0.001). Significance. All systems showed marginal gaps below 120 mu m and were therefore considered clinically acceptable. The CAD/CAM systems were more precise than the CAM system. (C) 2008 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.