Influence of framework configuration on the marginal adaptation of zirconium dioxide ceramic anterior four-unit frameworks

Abstract

Objective. To evaluate the influence of the framework configuration on the marginal adaptation of four-unit anterior fixed partial denture (FPD) frameworks made of partially sintered zirconium dioxide (ZrO₂) ceramics. Material and methods. Forty-eight standardized partially sintered ZrO₂ ceramic four-unit FPD frameworks were fabricated using three different CAD/CAM systems: Cercon Smart Ceramics (group CE), Vita YZ/Cerec In-Lab (group YZ/CL), and Xawex (group XA). Two different framework configurations (straight and curved) were manufactured for each group. The marginal adaptation of the frameworks was measured at 60 different points across the entire circumferential margin using a stereomicroscope. Marginal discrepancy values were compared between the two framework designs and between the three test groups using the t-test. The overall level of statistical significance was 5% after correcting the p-values using the Bonferroni–Holm method. Results. The following geometrical means of the marginal discrepancies were obtained for the curved/straight design: group CE, 120.0 μm/88.0 μm; group YZ/CL, 96.8 μm/86.5 μm; and group XA, 147.3 μm/113.4 μm. Significant differences were detected between the straight and curved designs for groups CE (p=0.001) and XA (p=0.003), but not for group YZ/CL (p=0.225). For both designs, the marginal discrepancies were significantly smaller in group YZ/CL than in group XA. For the curved design, the marginal discrepancies in group YZ/CL were also significantly smaller than those in group CE. Conclusions. Within the limitations of this study, the framework configuration influences the marginal adaptation of anterior four-unit FPD frameworks that are manufactured from partially sintered ZrO₂ ceramics independently of CAD/CAM system.