MARGINAL ADAPTATION OF THREE DIFFERENT ZIRCONIUM DIOXIDE THREE-UNIT FIXED DENTAL PROSTHESES

Statement of problem. Marginal adaptation is important for the long-term success of dental restorations. Data on the marginal discrepancy of zirconia-based fixed dental prostheses made with different computer-aided design/computer-aided manufacturing technology is needed. Purpose. The purpose of this study was to evaluate the marginal adaptation of different zirconia 3-unit fixed dental prostheses at different fabrication stages and after artificial aging. Material and methods. Twenty-four zirconia 3-unit fixed dental prostheses (DCS, Procera, and VITA YZ-Cerec; n=8) were fabricated using different manufacturing systems and conventionally cemented with glass ionomer cement on human teeth. Each group was aged in a masticatory simulator with thermal cycling. The marginal gaps were examined on epoxy replicas for frameworks and for restorations before and after cementation, and after masticatory simulation, at x250 magnification. Marginal adaptation was assessed using geometric means of the marginal gap values with 95% confidence intervals. Differences between the manufacturing systems and the effect of artificial aging were tested using repeated-measures ANOVA and post hoc paired and unpaired t tests with Bonferroni-Holm correction (alpha=.05). Results. The geometric mean (95% confidence limits) marginal gap values (mu m) for frameworks and for restorations before cementation, after cementation, and after masticatory simulation were, respectively: DCS: 86 (80-93), 86 (8390), 86 (78-94), and 84 (79-90); Procera: 82 (74-89), 89 (81-97), 89 (84-95), and 88 (82-94); and VITA YZ-Cerec: 64 (57-72), 67 (61-77), 76 (71-82), and 78 (76-80). The repeated-measures ANOVA showed significant group and stage effects (P<.05). Group VITA YZ-Cerec showed significantly smaller marginal gap values than groups DCS and Procera at framework (P<.05) and before-cementation (P<.05) stages. The VITA YZ-Cerec group showed significantly smaller marginal gap values than the Procera group after cementation (P<.05). The marginal gap values between different stages were not significantly different for all groups (P>.05). Conclusions. The marginal accuracy of zirconia fixed dental prostheses is influenced by manufacturing technique. (J Prosthet Dent 2009;101:239-247)