Mechanical Behavior of Ceramic Monolithic Systems With Different Thicknesses

Prior research has shown that ceramic materials are widely used in dental applications due to their aesthetic and mechanical properties. However, the mechanical behavior of these ceramics can vary significantly based on composition and thickness. Established knowledge includes the use of zirconia and lithium disilicate in dental prosthetics, with known differences in strength and durability. No prior work had resolved how thickness affects the fracture load of these materials when cemented on substrates. This gap motivated the need to evaluate how different ceramic types and thicknesses influence mechanical performance. The study of biaxial flexural strength and Weibull statistics has been used in prior work to assess ceramic reliability. However, the specific interaction between material type, thickness, and cementation remains unclear. This uncertainty drove the current investigation into the mechanical behavior of monolithic ceramic systems. The goal is to provide data relevant to clinical applications where ceramic thickness is a variable.

The aim of this study was to evaluate the mechanical behavior of three ceramic materials—fully stabilized zirconia (FSZ), partially stabilized zirconia (PSZ), and lithium disilicate (LD)—under different thicknesses and cementation conditions. The specific problem addressed is how ceramic type and thickness influence fracture load and flexural strength. The motivation comes from the clinical need to understand how these variables affect the performance of dental restorations. The study focused on comparing the mechanical properties of these ceramics when used in monolithic systems. The research sought to determine whether differences in composition and thickness lead to measurable changes in mechanical behavior. The study also aimed to assess whether cementation to a substrate alters the mechanical performance of these materials. The findings could inform material selection for dental prosthetics based on thickness requirements. The study sought to provide data that could guide clinical decisions regarding ceramic use and design.

The study used disk-shaped specimens of three ceramic types—fully stabilized zirconia (FSZ), partially stabilized zirconia (PSZ), and lithium disilicate (LD)—for mechanical testing. Specimens were fabricated with a diameter of 12 mm and thicknesses of 0.5 mm, 1 mm, and 1.5 mm for fracture load static tests. Biaxial flexural strength (BFS) was measured using a standard protocol with a sample size of 30 per group. Weibull statistics were applied to assess the reliability and variability of the mechanical data. Fracture load static tests (FLST) were conducted on specimens cemented to an epoxy-resin substrate. The study compared the mechanical performance of each ceramic type across thicknesses. Statistical analysis included one-way and two-way ANOVA to evaluate differences in strength and load. The Tukey post hoc test was used to identify specific differences between groups.

The highest biaxial flexural strength (BFS) was observed in PSZ with a mean of 683.0 MPa, followed by FSZ at 438.6 MPa, and LD at 248.6 MPa. One-way ANOVA confirmed significant differences in BFS among the three ceramic types. Weibull modulus values showed no significant differences across the materials. For fracture load static tests (FLST), PSZ showed higher values at 1.0 mm and 1.5 mm thicknesses compared to the other materials. At 0.5 mm thickness, all ceramics exhibited similar FLST values. LD at 1.5 mm thickness had a higher FLST than FSZ at the same thickness. Two-way ANOVA confirmed significant effects of ceramic type, thickness, and their interaction on FLST. The results suggest that both material composition and thickness significantly influence mechanical performance.

The authors propose that PSZ exhibits the highest biaxial flexural strength among the tested ceramics. They suggest that when cemented on a substrate, all materials with 0.5 mm thickness behave similarly in terms of fracture load. The researchers propose that LD, despite lower BFS, may offer comparable fracture load performance to FSZ when used in thicker forms. The study concludes that both material composition and thickness are important variables in determining mechanical behavior. The authors suggest that PSZ is more resilient to thickness variations than LD or FSZ. They propose that the choice of ceramic should consider both mechanical properties and intended thickness in clinical applications. The findings indicate that cementation to a substrate can influence mechanical performance. The authors suggest that these results may guide material selection for dental prosthetics based on thickness requirements.