Comparative Evaluation of Flexural Strength of Nano-zirconia-integrated Pressable Feldspathic and Lithium Disilicate Ceramics.

AIM: The purpose of the study was to evaluate and compare the flexural strength of nano-reinforced zirconia feldspathic porcelain, lithium disilicate ceramics, and zirconia. MATERIALS AND METHODS: Ten bar-shaped specimens of computer-aided design (CAD)/computer-aided manufacturing (CAM) zirconia, reinforced feldspathic porcelain, and reinforced lithium disilicate were fabricated in accordance to International Organization for Standardization (ISO 6872; n = 10). Feldspathic porcelain and lithium disilicate ceramic specimens were reinforced with 5, 10, 15, and 20% of zirconia nanoparticles through a customized technique. The specimens were subjected to three-point flexural strength test using universal testing machine (UTM) and examined for crack propagation using a scanning electron microscope (SEM). Oneway analysis of variance (ANOVA) and Tukey test were used to analyze the data (p < 0.05). RESULTS: The flexural strength of feldsphatic porcelain increased with the increase in the concentration of zirconia particles. The mean flexural strength of 5, 10, 15, and 20% nano-zirconia-incorporated lithium disilicate was 93.8, 97.1, 100.6, and 100.8 MPa respectively, and was lower than the control group (221.7 MPa). A significant difference in the flexural strength was found with the incorporation of nano-zirconia particles. CONCLUSION: The flexural strength of zirconia-integrated feld-spathic porcelain increased and lithium disilicate ceramics decreased with the nano-zirconia reinforcement. CLINICAL SIGNIFICANCE: The simplified approach of reinforcing feldspathic porcelain with zirconia nanoparticles can be adapted in clinical situations of higher masticatory forces.

Comparison of cytotoxicity between 3D printable resins and heat-cure PMMA.

Aim: The aim of this study was to evaluate and compare the cytotoxicity of polyurethane and polyoxymethylene printable resins with conventional heat cure polymethyl methacrylate denture base resins. Methods: The study followed ISO-10993-5 guidelines. It comprised of three groups. Fifteen cuboidal samples measuring 10x10 × 10mm dimension were prepared for each group. The polymethylmethacrylate samples were fabricated using conventional denture processing techniques, while the polyoxymethylene samples were printed using fused deposition modeling and the polyurethane samples using stereolithography technique. Post fabrication the samples were evaluated for cytotoxicity using the MTT assay with the VERO cell line. The percentage of cell viability was calculated to determine the cytotoxic effects. Results: Statistical analysis revealed a significant difference in the cell viability of the experimental groups (p ≤ 0.0001). The polyoxymethylene group showed the highest % cell viability (62.78 %), followed by the polymethylmethacrylate group (52.43 %), and the least was observed in the polyurethane-based resin group (46.47 %). The findings indicate polyoxymethylene group displayed least cytotoxicity, followed by polymethylmethacrylate, and polyurethane-based resin. Conclusion: Polyoxymethylene resin exhibited the minimum cytotoxic properties among the tested materials, followed by polymethylmethacrylate and polyurethane resin.