*2.5. Statistical Analysis*

All statistical analysis was performed using SPSS 12 for Windows (SPSS Inc., Chicago, IL, USA). A one-way analysis of variance with Tukey's post-hoc test was used to evaluate the differences between each group after performing a test of normality. A *p*-value less than 0.05 was set as the threshold for statistical significance.

#### **3. Results**

## *3.1. Formation of Cell Spheroids with Human Gingiva-Derived Stem Cells*

Spheroids were well-established in each microwell on Day 1 (Figure 2). Furthermore, no noticeable changes in the shape of the cell spheroids were observed with the addition of BMP-4 at concentrations of 2, 6, or 10 ng/mL. There were no noticeable changes at the longer culturing times. The spheroid diameters are shown in Figure 3. There was a general decrease in the diameter of the spheroids with longer incubation time.

**Figure 2.** Spheroid morphology on Days 1, 3, 5, and 7. The scale bar indicates 200 μm.

**Figure 3.** Diameter of the spheroids on Days 1, 3, 5, and 7. The spheroids were treated with BMP-4 at concentrations of 0, 2, 6, or 10 ng/mL.
