2.4.2. X-ray Diffraction

The crystallographic features of the deposited films were examined using an X-ray diffractometer (JDX-3500, JEOL Ltd., Tokyo, Japan) with Cu Kα radiation (λ = 0.1541 nm) at room temperature. The 2θ range was 20–80◦, and the XRD profile was recorded at step-scan intervals of 0.02◦ at a scanning speed of 8.0◦/min at 40 kV and 150 mA.

#### 2.4.3. Measurement of the Contact Angle of Water Droplets on the Surfaces

To evaluate the wettability of the titanium disks before and after surface treatment, the contact angle of the water droplets (20 μL) on the surfaces was measured using a contact angle analyzer (Phoenix Alpha, Seoul, Korea) at 0, 3, 7, and 14 days after each surface treatment.

#### *2.5. Evaluation of Cytocompatibility*

#### 2.5.1. Cell Line

The MC3T3E1 cell line was used in this study to evaluate the cell attachment of the titanium samples before and after SPT.

2.5.2. Attachment of Cells on Differently Modified Titanium Surfaces after Four Hours of Incubation

There were 6 groups for each experiment, that is, 30-day aged ("Polished-Ti" and "Ti-AT-SPT"), 7-day aged ("Polished-Ti" and "Ti-AT-SPT"), fresh "Polished-Ti", and fresh "Ti-AT-SPT". Four specimens from each group were placed on a 24-well plate, disinfected with 1 mL of 70% ethanol

for 10 min and washed with sterilized distilled water for 10 min. The number of MC3T3E1 cells was adjusted to be 5 × 104 cells/mL in a regular medium consisting of <sup>α</sup>-modified minimum essential medium (α-MEM; with L-glutamine and phenol red, Wako Pure Chemical Industries Ltd., Osaka, Japan) supplemented with 10% heat-inactivated fetal bovine serum. Adjusted cells were seeded on a sample with 1 mL per well. After 4 h of incubation under a humidified atmosphere of 5% CO2 at 37 ◦C, the cells were detached by trypsin-EDTA (0.25% Trypsin/0.53 mM EDTA in Hanks Balanced Salt Solution without calcium or magnesium) and the number of cells was counted by a hemocytometer.

#### 2.5.3. Statistical Analysis

Statistical analysis was performed using one-way analysis of variance (ANOVA), and the Games–Howell post hoc test with the significance level of *p* < 0.05.
