On the mechanical properties of monolithic and laminated nano-ceramic resin structures obtained by laser printing

The purpose of this study was to evaluate the mechanical properties of laser printed monolithic and laminated nano ceramic resins (NCR) for dental prosthetic applications. Three different types of discs were produced by laser printing: monolithic NCR discs and laminated NCR discs with 100 mu m (laminate_100) and 500 mu m (laminate_500) resin interlayers (n = 10). To assess the adhesion strength of the photosensitive resin used as interlayer to the NCR, cylindrical specimens were produced. The biaxial flexural strength and shear bond strength of the specimens were measured using a universal testing machine. Data was statistically analyzed by one-way ANOVA followed by Tukey HSD test (alpha = 0.05). The microstructure and fracture surfaces were analyzed by SEM/EDS. Results were rationalized with finite element analysis (FEA). Laminate_100 specimens showed significantly higher flexural strength (similar to 50%) than monolithic and Laminate_500 specimens (p < .05). A good adhesion between the resin used as interlayer and the NCR was registered. FEA revealed a more favorable stress distribution in laminates with a thinner interlayer. Modern CAD/CAM systems can be used in the direct manufacturing of correctly designed laminated structures displaying enhanced strength and damage tolerance relative to conventional monolithic ones, thereby positively impacting their clinical performance.