Influence of contemporary CAD-CAM milling systems on the fit and adaptation of partially stabilized Zirconia fixed partial dentures

To evaluate marginal fit and internal adaptation of three-unit Zr frameworks fabricated from four Zr CAD/CAM milling systems. Fixed partial denture models were replicated (40 stone models) using Polyvinyl Siloxane impression material (PVS) and type IV stone for Zr framework fabrication. FPDs were milled with four CAD/CAM systems, Group-II: LAVAL Zirconia milled by LAVA , Group-2: Vita In-Ceram YZ milled by Cerec®, Group-3: Zirconia milled by GM1000 and Group-4: Zirconia milled by DWX-50N. Twelve marginal gap measurements per framework were performed at pre-established points, with a metallurgical microscope (Zeiss, Germany) at 500X magnification. Eight measurements of cement space per section were performed for adaptation. Data was analyzed using ANOVA and Tukey post hoc test. Zirconia FPD frameworks exhibited gaps ranging from 16 to 50.1 µm for marginal fit and 26.8 to 102.5 µm for internal adaptation. Group-3 [20.8 (8.3) µm & 50.3 (11.4) µm] and Group-4 [16.0 (4.0) µm & 40.2 (8.8) µm] specimens showed significantly lower marginal fit and internal adaptation gaps compared to Group-I [50.1 (13.4) µm & 100.5 (16.7) µm] and Group-2 [38.9 (8.2) µm & 102.5 (13.4) µm] specimens respectively. Different CAD-CAM systems for fabrication of Zr FPD frameworks displayed a significant influence on marginal fit and internal adaptation of restorations.