Effects of different Er,Cr:YSGG laser parameters on dentin shear bond strength and interface morphology: an in vitro study

Purpose: The aim of this in vitro study is to evaluate the effect of Er,Cr:YSGG laser parameters, specifically power (Watt) and frequency (Hertz), throughout both, shear bond strength (SBS) and dentin-composite interface morphology, when using laser etch as an alternative to acid etching with a “two-step” total etch adhesive. Methods: Thirty-six human sound molars were mounted on acrylic blocks, randomly divided into six groups, six teeth into each group, where five teeth were selected for the SBS test, and one sectioned for the scanning electron microscope (SEM) analysis. Teeth were sliced occlusally to expose a flattened dentin surface, then grouped according to various treatments: control group, only treated with phosphoric acid etchant; and groups 1–5, only treated with Er,Cr,:YSGG laser irradiating at 3 W/25 Hz, 3 W/50 Hz, 4 W/25 Hz, 4 W/50 Hz, and 5 W/75 Hz respectively. The adhesive was applied followed by composite build up. SBS test was carried out using a universal testing machine. The resin-dentin interface was analyzed utilizing a SEM. Results: The control group showed the highest SBS values (11.38 ± 2.03 Mpa). Group 5 (5 W/75 Hz) was the second highest (8.46 ± 1.82 Mpa), yet the highest among the entire laser-irradiated groups, showing a marginal/borderline significance with the control group (P = 0.044). Group 3 (4 W/25 Hz) came second through the laser samples (7.41 ± 0.97 Mpa). SEM analysis manifested premier retentive composite dentin interface among the control group and groups 5 and 3. Conclusion: When applying Er,Cr,:YSGG laser solely for dentin etching, adjusting the settings to a power of 5 W and frequency at 75 Hz will lead to optimum results regarding both SBS and interface morphology.