Margin quality, homogeneity, and internal porosity assessment of experimental short fiber-reinforced CAD/CAM composite

Objectives: 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 microstructure, homogeneity, and porosity of the SFRC CAD compared with other commercial CAD/CAM materials.

Methods: 40 anterior crowns were milled from five CAD/CAM blocks divided into five groups (n = 8/group). The first group was made of lithium disilicate ceramic blocks (EM), the second of zirconia-reinforced lithium disilicate blocks (CD), the third of hybrid polymer-infiltrated ceramic network blocks (VE), the fourth of hybrid nanoparticle-filled resin blocks (CS), and the last of SFRC CAD blocks (SFRC). Crowns were inspected with stereomicroscope and margins irregularities were measured using FIJI software. Specimens were scanned using micro-CT to investigate porosity and homogeneity. Crowns were then subjected to cyclic fatigue aging (120,000 cycles, Fmax = 220 N) and margin irregularities were measured again. SEM/EDS and XPS analyses were employed.

Results: SFRC CAD group resulted in the least margin irregularity values compared to other groups before and after cyclic fatigue aging, and lithium disilicate group resulted in the highest margin irregularity values (p < 0.05). Micro-CT scanning revealed a homogenous distribution of fillers of tested materials with low internal porosity.

Significance: Material type and fatigue aging significantly affect crown margin irregularities. Hybrid and resin-based groups resulted in less margins irregularities than ceramic-based ones. All tested materials have homogenous structures with low internal porosity within the range of imaging resolution.