2.1. Specimen Fabrication

Disks with a diameter of 10 mm and thickness of 5 mm were produced and underwent SLA surface treatment, as performed by a dental implant manufacturer (DENTIS; Daegu, Republic of Korea) (N = 12 per surface treatment group). The composition of the Ti disks (grade 4) included 0.08% carbon (C), 0.5% iron (Fe), 0.015% hydrogen (H), 0.05% nitrogen (N), 0.40% oxygen (O), and 98.9% Ti. The zirconia disks were solely composed of ZrO₂ (Y-TZP) without any other additives. The zirconia consisted of 93.0 wt% ZrO₂, 5.0 wt% Y₂O₃, 0.1 wt% Al₂O₃, and 1.9 wt% HfO₂, with a grain size of 0.3 µm. Zirconia disks without any surface treatment were classified as the machined group (M group).

Titanium disks underwent sandblasting via a sandblasting with large-grit alumina particles for 20 s under 4 bar pressure. Subsequently, they were acid-etched using a mixture of HCL and H₂SO₄, diluted with distilled water, and air-dried at room temperature. The resulting specimens were categorized as the titanium SLA surface group (T group).

According to the previous study, we determined the desired form and the parameters [17]. In this study, a custom femtosecond laser system with very short pulses was used for surface treatment of the zirconia disks. Using this system, a linear pattern with 50 µm grooves was formed on the zirconia disk surface at a speed of 10 mm per second using a laser with a wavelength of 343 nm. These zirconia disks were categorized as the hydrophilic with a femtosecond laser group (HF group).

Using a custom nanosecond laser system, a grid pattern with 200 µm grooves was formed on the zirconia disk surface at a speed of 100 mm per second using a laser with a wavelength of 355 nm. These zirconia disks were categorized as the hydrophobic with a nanosecond laser group (HN group).

In the present study, specimens with all surface treatments completed were cleaned and sterilized by the implant manufacturer (DENTIS; Daegu, Republic of Korea) and were packaged to prevent contamination.