Marginal Fit of Implant-Supported All-Ceramic Zirconia Frameworks
This study evaluated the effect of fabrication techniques and cyclic loading on the vertical marginal fit of implant-supported fixed partial denture (FPD) frameworks. Thirty implant-supported 3-unit FPD frameworks were fabricated on a model system, divided into 3 equal groups (n = 10). The first group (control) was constructed from base metal alloy; the other 2 test groups were constructed from all-ceramic zirconia using a computer-aided design/computer-aided manufacturing (CAD/CAM) Cerec 3 system and a copy milling (Zirkonzahn) system. A cyclic load of 200 N was applied to each framework for up to 50,000 cycles. Linear measurements were made in micrometers of the vertical gap between the framework and the implant-supported abutment at 16 predetermined points before and after cyclic loading. The frameworks were viewed using scanning electron microscopy to inspect any fractographic features. One-way analysis of variance was performed to compare the marginal discrepancy values of the control and the 2 test groups and for each group; a t test was applied to determine whether significant changes in the fit were observed after cyclic loading (α = 0.05). The CAD/CAM group showed significantly higher marginal gap mean values (80.58 μm) than the Zirkonzahn and control groups (50.33 μm and 42.27 μm, respectively) with no significant difference. After cyclic loading, the CAD/CAM group recorded the highest marginal gap mean value (91.50 ± 4.260 μm) followed by control group (72.00 ± 2.795 μm); the Zirkonzahn group recorded the lowest marginal gap (65.37 ± 6.138 μm). Cyclic loading significantly increased the marginal gap mean values in the control group only. A marginal chip was observed in one of the CAD/CAM ceramic frameworks. Within the limitations of this study, the fabrication technique influenced the marginal fit of the implant-supported 3-unit FPD frameworks. Cyclic loading failed to change the fit of all-ceramic zirconia frameworks, whereas significant changes were found in the metal frameworks.
Figure 1. Model system. Figure 2. Metal framework. Figure 3. All-ceramic zirconia framework. Figure 4. A column chart of marginal gap mean values for all groups before and after cyclic loading. Figure 5. Column chart of the marginal gap mean values for all groups as a function of cyclic loading.
Figure 6. Stereomicroscopic photograph (50×) showing the vertical marginal gap and a minor chip at the gingival margin of the computer-aided design/computer-aided manufacturing (CAD/CAM) sample. Figure 7. Scanning electron microscopy (SEM) photograph (at 14×) of one of the CAD/CAM samples showing a minor chip at the gingival margin of the buccal side. Figure 8. The SEM photographs of the failure site of the CAD/CAM sample showed at (a) 60× arrest line. A higher magnification (300× and 1000×) of the squared area pictured in (a) shows (b) a wake hackle and (c) a hackle indicating the direction of the crack propagation toward the margin. Figure 9. The SEM photographs of the Zirkonzahn sample at (a) 300× and (b) 1000× showed no fractographic features.
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