Effects of TiO(2)-Coated Stainless Steel Orthodontic Wires on Streptococcus mutans Bacteria: A Clinical Study

INTRODUCTION: The aim of this study was to clinically evaluate Streptococcus mutans adhesion on titanium dioxide–coated stainless steel orthodontic wires to decrease white-spot formation. METHODS: In this study, four groups of 17 patients each (n=68) aged 12–25 years participated. A titanium dioxide coating layer was deposited on 0.4572 mm stainless steel orthodontic wires using physical vapor deposition. The coated wires were randomly assigned to one jaw, and the opposite jaw received an uncoated wire as control. Patients were divided into groups according to the duration that wires were in their mouths: A) 1 week, B) 2 weeks, C) 3 weeks, and D) 4 weeks. Block randomization was used to assign patients to each group. At the end of the experiment, 20 mm of each wire (canine-to-canine area) was cut and cultured in S. mutans–specific medium. The culture plates were placed in an incubator containing 5% CO(2) for 72 hours at 37°C, and then colonies were counted. MTT was used to test the biocompatibility of the coated and uncoated wires. To evaluate the stability of the coated titanium dioxide layer on the wires, titanium concentration on the saliva was determined using inductively coupled plasma mass spectroscopy. RESULTS: The Kruskal–Wallis test showed that there was no significant difference in colony counts among the coated wires during 1–4 weeks (p<0.48). In the uncoated-wire groups, colonys count at week 1 were higher than weeks 24 –(p<0.022). Wilcoxon’s test showed that the number of colonies was significantly different in groups A and C, but there was no significant difference in groups B or D. MTT-assay results showed that there was not a significant difference between cell viability in the coated-wire group and the control. The Kruskal–Wallis test showed that there was no significant difference in titanium concentration in the studied groups (p<0.834). CONCLUSION: Application of titanium dioxide coating is effective in reducing bacterial adhesion at wire insertion.