Table 1. Composite resin materials used in the study.

Type of composite	Composition		Manufacturer
	Inorganic matrix	Fillers
Ceram.X SphereTec One	Poly-urethane-methacrylate Bis-EMA TEGDMA	• Spherical, prepolymerized SphereTEC™ fillers (d3,50 ≈ 15 μm) • Non-agglomerated barium glass (d3,50 ≈ 0.6 μm) and ytterbium fluoride (d3,50 ≈ 0.6 μm)	Dentsply, UK
Filtek Z 350XT	Bis-GMA UDMA TEGDMA Bis-EMA PEGDMA	• Non-aggregated 20 nm silica, 4–11 nm zirconia • Aggregated zirconia/silica clusters	3M ESPE, United States