Fracture Resistance of Functionally Graded Three-unit Fixed Partial Denture with Titanium Dioxide and Silica Nanoparticles: An In Vitro Study

Abstract

Purpose: The objective of this study was to assess the fracture resistance of functionally graded monolithic zirconia with different nanoparticles in three-unit fixed dental prostheses (FDPs) after undergoing thermal and mechanical aging. Materials and methods: A total of 32 three-unit monolithic zirconia prostheses were machined and randomly assigned to four groups (n = 8 each) as Group A - control group (without any nanoparticle), Group B - titania sol group, Group C - silica sol group, and Group D - silica and titania nano-sol group. Grading with nanoparticles was carried out on presintered monolithic zirconia and then was sintered. Fixed prostheses were exposed to thermocycling for 5-55°C for 10,000 cycles. The long-term clinical performance of monolithic zirconia was assessed by quasistatic fracture strength of 0-300 N for 1,00,000 cycles. After following loading conditions, prostheses were loaded until fracture. Fracture mode and evaluation of nanoparticles were seen under a field-emission scanning electron microscope (FE-SEM). Energy dispersive spectroscopy (EDS) was done to find an elemental composition of nanoparticles in zirconia. Weibull's modulus implies the reliability of material for each of the four materials. Kruskal-Wallis analysis of variance (ANOVA) followed by a post hoc test done for the between-group differences in the maximum load-bearing capacity of the four groups. Results: Significant variance (p = 0.001) in the fracture resistance of three-unit FDPs after mechanical and thermal cycling was observed. The fracture resistance of the control group A (703.60 N) was significantly lesser than that of the titania sol group B (1031.35 N) and silica and titania nano-sol group D (1094.74 N). Weibull moduli values of all four groups are as follows in descending order groups D > A > B > C. Conclusion: Functional grading of monolithic zirconia with silica and titanium dioxide nanoparticles can increase the fracture resistance of three-unit FDPs after aging. The addition of titanium to zirconia has been shown to increase the Weibull modulus, which corresponds to a higher level of homogeneity of the material and more excellent reliability as a structural material.