The results showed that acid treatment of the titanium surfaces for 20 or 60 min did not affect cell proliferation, either after 24 h (p = 0.484), 48 h (p = 0.698), or 72 h (p = 0.287) (Fig. 2a).

For the cell viability test, loss of viability was observed for the machined surface after 48 h of culture compared to the groups submitted to acid treatment for 20 or 60 min, which did not differ statistically between each other (Fig. 2b). No significant difference between groups regarding cell viability was verified after 24 h (p = 0.590) and 72 h (p = 0.799).

As for type I collagen synthesis, the lowest yields were observed on acid-treated surfaces, regardless of the application times (20 min or 60 min) after 48 h (Fig. 3). One-way ANOVA showed no significant difference between the groups regarding the expression of type I collagen at 24 h and 72 h.