Effect of hydrofluoric acid and femtosecond laser application sequence on nano-lithium silicate CAD/CAM ceramic bonding: an in vitro study.

Authors

Remzi Fırat, Berivan Dündar Yılmaz

Published in

BMC oral health. Jul 20, 2026. Epub Jul 20, 2026.

Abstract

This in vitro study investigated whether the sequence of combining hydrofluoric acid (HF) etching and femtosecond Ti: Sapphire laser irradiation influences the surface roughness (Ra) and shear bond strength (SBS) of a nano-lithium silicate CAD/CAM ceramic (Amber Mill; HASS Bio Core). Ninety rectangular block-shaped specimens (5 mm × 7 mm × 3.5 mm) were allocated to nine groups (n = 10): untreated control; HF only applied before or after crystallization; femtosecond laser only applied before or after crystallization; HF followed by laser (HF→Laser) applied before or after crystallization; and laser followed by HF (Laser→HF) applied before or after crystallization. Ra was measured with a contact profilometer (Mahr M2); surface morphology was evaluated by field emission scanning electron microscopy (GeminiSEM 300; ZEISS, Germany); and crystalline phase integrity was verified by X-ray diffraction (Rigaku DMAX-2200). Shear bond strength was determined after thermocycling (5000 cycles, 5-55 °C) using a universal testing machine (Instron Model 1082). Data were analysed with one-way ANOVA and Tukey HSD post hoc test; a supplementary two-way ANOVA (crystallization stage × treatment protocol) performed on the eight treatment groups further confirmed that application sequence remained a significant factor for both Ra and SBS (p < 0.001); the Ra-SBS correlation was assessed with Pearson's coefficient (α = 0.05). Application sequence significantly affected both Ra and SBS (p < 0.01). Combined protocols consistently outperformed single-treatment protocols in SBS. The post-crystallization Laser→HF group achieved the highest SBS (19.295 ± 2.881 MPa), while the post-crystallization HF→Laser group produced the greatest Ra (1.538 ± 0.058 μm). A moderate positive Ra-SBS correlation was identified (r = 0.411; p < 0.01). FE-SEM and XRD analyses confirmed that neither protocol altered the fundamental crystalline phase of the material. Within the limitations of this study, application sequence is a critical determinant of bonding performance in nano-lithium silicate CAD/CAM ceramics; the post-crystallization Laser→HF combined protocol is recommended for optimal resin-cement adhesion.

PMID:
42472811
Bibliographic data and abstract were imported from PubMed on 20 Jul 2026.

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