Evaluation of Experimental Short Fiber-reinforced CAD/CAM Composite Using Micro-CT and SEM : (Crown Margin Quality, Chemical Microstructure, Porosity, and Homogeneity)

Abstract

The aim of this study was to evaluate the margin quality of anterior crowns made of experimental short fiber-reinforced CAD/CAM composite (SFRC CAD) block before and after cyclic fatigue aging. Moreover, to investigate the chemical microstructure, homogeneity, and porosity of the SFRC CAD in comparison with other commercial CAD/CAM materials. 40 anterior crowns were milled from five CAD/CAM blocks divided into five groups (n=8/group). The first group made of lithium disilicate ceramic blocks, the second made of zirconia-reinforced lithium disilicate blocks, the third made of hybrid polymer-infiltrated ceramic network blocks, the fourth made of hybrid nanoparticle-filled resin blocks, and the last made of SFRC CAD blocks. Crowns were inspected with stereomicroscope and margins discrepancies were measured. Specimens were scanned using micro-CT to investigate the porosity and homogeneity. The same crowns were subjected to cyclic fatigue aging (120,000 cycles, Fmax=220 N) margin discrepancies were measured again. SEM/EDS and XPS analyses were employed. SFRC CAD group resulted in the least margin discrepancies compared to other groups before and after cyclic fatigue aging, while IPS e.max group resulted in the highest margin discrepancy values (p<0.05). Micro-CT scanning revealed a homogenous distribution of the fillers of the tested materials with low porosity. After cyclic fatigue aging test, the SFRC CAD crowns have the highest survival rate, followed by IPS e.max. Material type and fatigue aging can significantly affect crown margin quality, with hybrid and resin-based groups resulted in better margin quality than ceramic-based ones. All tested materials have homogenous structure with extremely low porosity.