Table 1 Composition of the materials used in the study

3 M ESPE, St. Paul, MN, USA

Organic: 20 wt.% resin matrix (Bis-GMA, UDMA, Bis-EMA, TEGDMA)

Fillers: SiO₂ (20 nm), ZrO₂ (4–11 nm), ZrO₂/SiO₂ nanoclusters (0.6–10 nm)

Filler content: 80 wt.% nanoceramic

Resin nano ceramic

Lava Ultimate CAD/CAM blocks

GC Corporation, Tokyo, Japan

Organic:29 wt.% resin matrix (UDMA, DMA, Bis-MEPP)

Fillers: barium glass (300 nm),

SiO₂ (20 nm)

Filler content: 71 wt.% nanoparticles

Flexible nano ceramic

Cerasmart

CAD/CAM blocks

Ultradent; South Jordan, UT, USA

Hydrofluoric acid 9% buffered

Hydrofluoric acid gel

Ultradent

Porcelain Etch

Renfert GmbH, Hilzingen, Germany

99.5% Al₂O₃ (50 μm), SiO₂ < 0.06%

Grit blasting particles

Cobra 50-μm Al₂O₃ powder