Evaluation of the Antimicrobial properties and flexural strength of self cured acrylic resin used in removable orthodontic appliances coated by nano and micro layers of titanium nitride

Abstract

Objective: This study aimed to compare the antibacterial properties, flexural strength, hydrophobicity, and adhesion properties of acrylic resin coated with titanium nitride (TiN) and uncoated acrylic resin samples. Methods: In this in-vitro study, 60 self-cure acrylic samples were coated with TiN in nano and micro thicknesses using the magnetron sputtering technique. The thickness and morphology of coatings were determined by SEM. Constituent elements of samples were assessed using EDAX. The anti-bacterial properties of TiN against Staphylococcus aureus, Escherichia coli, and Streptococcus mutans were evaluated. The flexural strength test (three-point flexural test) was performed and the contact Angle test and Cross-cut adhesion test were assessed. The data was analyzed using SPSS 22.0. One-way ANOVA and Tukey’s Post Hoc were applied at the significance level of 0.05. Results: EDAX results showed that all coated samples consisted of titanium and nitrogen elements. The number of colonies was significantly different against Staphylococcus aureus, Escherichia coli, and Streptococcus mutans among the study groups. In four coated groups, the number of colonies of Staphylococcus aureus was fewer than Escherichia coli and the number of colonies of Escherichia coli was fewer than Streptococcus mutans. There was no significant difference between the study groups in terms of flexural strength. The coated samples were hydrophobic while the control group was hydrophilic. The adhesion of the TiN coating layer to the acrylate substrate was suitable. Conclusion: It can be claimed that the coating of acrylic resin used in removable orthodontic appliances with TiN nano-layers and micro-layers induces antibacterial and hydrophobic properties in acrylic resin, without having a negative effect on its flexural strength.