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<p>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&#xa0;mm × 7&#xa0;mm × 3.5&#xa0;mm) were allocated to nine groups (<i>n</i> = 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&#xa0;°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 (<i>p</i> &lt; 0.001); the Ra–SBS correlation was assessed with Pearson’s coefficient (α = 0.05). Application sequence significantly affected both Ra and SBS (<i>p</i> &lt; 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&#xa0;MPa), while the post-crystallization HF→Laser group produced the greatest Ra (1.538 ± 0.058&#xa0;μm). A moderate positive Ra–SBS correlation was identified (<i>r</i> = 0.411; <i>p</i> &lt; 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.</p>

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

  • 期刊论文

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  • 发表日期：

    2026年7月20日

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  • Remzi Fırat,
  • Berivan Dündar Yılmaz

摘要

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.