Comparative short-term in vitro analysis of mutans streptococci adhesion on esthetic, nickel-titanium, and stainless-steel arch wires

Objective: To test the hypothesis that there are no differences in mutans streptococci (MS) adhesion between esthetic and metallic orthodontic arch wires based on their surface characteristics. Materials and Methods: Surface roughness (R-a) and apparent surface free energy (SFE) were measured for six wires four esthetic, one nickel-titanium (NiTi), and one stainless-steel (SS)-using profilometry and dynamic contact angle analysis, respectively. The amount of MS (Streptococcus mutans and Streptococcus sobrinus) adhering to the wires was quantified using the colony-counting method. The surfaces, coating layers, and MS adhesion were also observed by scanning electron microscopy. Statistical significance was set at P < .05. Results: The Ra values of the esthetic wires were significantly different from one another depending on the coating method (P < .05). The NiTi wire showed the highest SFE, followed by the SS wire and then the four esthetic wires. The NiTi wires produced a significantly higher MS adhesion than did the SS wires (P < .05). The esthetic wires showed significantly lower MS adhesions than did the NiTi wire (P < .05). Pearson correlation analyses found moderate significant positive correlations between the SFE and the S mutans and S sobrinus adhesions (r = .636/.427, P < .001/P = .001, respectively). Conclusions: The hypothesis is rejected. This study indicates that some esthetic coatings on NiTi alloy might reduce MS adhesion in vitro in the short term.