A customized silicon mold with a thickness of 2 mm was fabricated to be used in the composite bonding procedure. A 3‐mm circular hole was made in the center of this mold. The mold was placed within the center of the enamel/dentin surface. In the acid‐etched groups (EA and DA), the demarcated surfaces were etched with 37% (v/v) phosphoric acid (Total Etch; Ivoclar Vivadent, Schaan, Liechtenstein) for 30 s, washed, and dried. In the laser‐conditioned groups (EL and DL), the demarcated surfaces were etched with Er,Cr:YSGG laser (Waterlase iPlus; Biolase, Irvine, CA, USA) and the laser tip (MZ8, 6 mm in length) was applied perpendicular to the tooth surface and moved slowly along the surface for 30 s with 0.5‐mm distance from the surface in scanning mode. The laser had a wavelength of 2780 nm, power of 4.50 W, 50 Hz frequency in H mode, 60% air, 30% water spray, pulse duration of 140 μs, energy density of 90 mJ/pulse, and 800 nm spot size.

Following the above treatments, all 80 specimens were ready for the application of the total‐etch adhesive system (ExciTE F; Ivoclar Vivadent, Schaan, Liechtenstein) per manufacturer's instructions. Resin composite (Filtek Z250XT Universal Restorative; 3M ESPE, St. Paul, MN, USA) was applied to the enamel and dentin surfaces and packed gently with a plastic instrument. A very thin celluloid strip was placed on top of the composite to stabilize it. The composite was vertically light‐cured for 20 s with a previously calibrated LED light‐curing device (Bluephase G2; Ivoclar Vivadent, Schaan, Liechtenstein) per manufacturer's instructions. The celluloid strip and mold were gently removed, and the samples were cured again for 20 s. All the materials used are described in Table Table11.

Description of materials used

Phosphoric acid acrylate, hydroxyethyl methacrylate, methacrylate

(%, g/v)


Highly dispersed silica


Catalysts, stabilizers, fluoride

The filler system:

Surface‐modified zirconia/silica with a median particle size of ≤3 μm

Non‐agglomerated/non‐aggregated 20‐nm surface‐modified silica particles

The filler loading was 82% by weight (68% by volume)

The resin system: