In Vitro Study of Comparative Evaluation of Marginal and Internal Fit between Heat-Pressed and CAD-CAM Monolithic Glass-Ceramic Restorations after Thermal Aging

Abstract

The accuracy of newly developed ceramic materials is still being studied. Marginal and internal adaptation are known factors that have an essential impact on the long term success of dental restorations. The aim of this in vitro study was to evaluate the marginal and internal fit of heat-pressed and milled monolithic glass-ceramic restorations based on their ceramic type, processing technique, and in vitro thermocycling. Thirty-two crowns were studied and divided into four groups (n = 8), according to the ceramic material (feldspathic glass-ceramic (F) and zirconia reinforced lithium silicate glass-ceramic (ZLS)) and to their technological obtaining processes (milling (M) and heat-pressing (P)). A typodont preparation was scanned with a D2000 3D scanner to obtain identical 32 resin 3D-printed abutment teeth. Marginal and internal gaps were measured using the silicone replica technique under 40× magnification. The crowns were further cemented and thermally aged for 10,000 cycles After cementation and thermocycling of the samples, marginal and internal gaps were assessed using micro-CT (micro-computed tomography)) analysis. Data were statistically analyzed using statistical tests. Significant differences were found before and after cementation and thermocycling among the tested materials (p < 0.05). Related to technological processing, significant differences were seen in the marginal area between FP and FM (p < 0.05) Significant differences were also found in the axial and occlusal areas between the ZLSP and ZLSM. Thermocycling and cementation did not have a significant effect on the tested materials (p < 0.05). The technological processes influenced the marginal and internal fit of the crowns in favor of the CAD/CAM (computer aided design/computer aided manufacturing)technologies. Thermal aging had little effect on marginal adaptability; it increased the values for all the tested samples in a small way, but the values remained in their clinically acceptable range for all of the crowns.

Evaluation of Marginal/Internal Fit and Fracture Load of Monolithic Zirconia and Zirconia Lithium Silicate (ZLS) CAD/CAM Crown Systems

“…The reasons for the differences could possibly be attributed to the type of abutment used for evaluation (natural tooth abutment replica in the present study versus implant abutment in the other study), crown fabrication technique employed, and software used. The mean marginal gaps in the present study (39.5 ± 7.4 µm) showed similarities with the numbers reported in a recent study, of 38.4 ± 4 µm [ 67 ], but they were also in disagreement with some others, e.g., 77.9 ± 36.7 µm [ 68 ] and 85 ± 40 µm [ 30 ]. The disparities in the mean marginal gap between the present and earlier papers and the relative small marginal gaps seen in this report might be ascribed to the CAD/ CAM system/5-axis milling machine used, milling bur condition, crystallization parameters set, laboratory technician skill and experience, fit evaluation method used, abutment preparation design/margin configuration, and the effect of no cementation.…”

“…Still, research on the marginal and internal adaptation of monolithic zirconia CAD/CAM crowns has mostly been restricted and is especially lacking with the anatomically contoured translucent partially stabilized zirconia (PSZ) and ZLS crowns [ 20 , 21 , 28 , 29 ]. To the authors’ best knowledge, studies evaluating the fit accuracy of complete coverage crowns using nano-computed tomography (CT) methods are also rare, although micro-CT evaluation of indirect fixed restorations has been reported in several papers [ 28 , 30 , 31 ].…”

Evaluation of Marginal Fit and Fracture Resistance of Zirconia Implant Abutment Supporting Two Types of Metal Free CAD/ CAM Restorations

“…Some studies reported values between 40 and 120 μm (28,29) . 200-300 μm was reported as wider marginal discrepancy in other studies (30,31) . Based on these proposals, two metal free CAD/CAM restorations (zirconia and breCAM.BioHPP) were assessed in the current study are clinically appropriate with respect to marginal accuracy.…”

Fractographic and Microhardness Evaluation of All-Ceramic Hot-Pressed and CAD/CAM Restorations after Hydrothermal Aging

“…Studies have shown that, when comparing ZLS and feldspathic glass-ceramics, the best fatigue behavior was statistically presented by the ZLS ceramic because of its reinforced microstructure [ 18 ]. Since their development, several studies have researched ZLS and feldspathic glass-ceramics milled or hot-pressed [ 19 , 20 , 21 , 22 , 23 , 24 , 25 ].…”