Evaluation of antibacterial activity and shear bond strength of orthodontic adhesive containing chitosan nanoparticles
Saudi Digital Library
Aim and Hypothesis: The study aimed to investigate the effect of orthodontic adhesive that contains various sizes of chitosan nanoparticles (CS-NPs) on Streptococcus mutans growth, enamel integrity, and shear bond strength. The research hypotheses were, first, that smaller-sized chitosan nanoparticles combined with an orthodontic adhesive will reduce white spot lesions when compared to larger-sized chitosan nanoparticles. Second, chitosan nanoparticles combined with an orthodontic adhesive will not affect the shear bond strength. Methods: The antimicrobial activity was tested in two stages. In stage 1, disc agar diffusion test was used. Four 6-mm wells were created in the petri dishes and each was inoculated with 80 µl of broth (negative control), chlorhexidine (CHX, positive control), CS-NPs (20 nm), or CS-NPs (131 nm). In stage 2, a total of 24 teeth were randomly divided into three groups. In group 1 (control), the brackets were bonded with an adhesive with no treatment (Transbond XT), in group 2 the adhesive was blended with CS-NPs (20 nm), and in group 3 the adhesive was blended with CS-NPs (131 nm). Caries assessment and enamel integrity were measured using the International Caries Detection and Assessment System (ICDAS) and the profilometry machine. To measure the shear bond strength, the teeth were placed in an occlusal gingival direction and the occlusal load was directed parallel to the tooth surface. All readings were recorded by an Instron machine in MPa. One-way ANOVA was performed to compare the means of the zones of inhibition, shear bond strength, and enamel integrity, followed by post hoc Tukey’s multiple comparison test. Results: CS-NPs significantly reduced the growth of S. mutans when compared to the control (p = 0.024); however, no statistical significance was noted between the 2 sizes (20 nm and 131 nm, p>0.99). Furthermore, orthodontic adhesive that contained chitosan nanoparticles showed comparable shear bond strength to the control (p = 0.466). For carries assessment, the weighted kappa was (0.87) indicating an excellent agreement between the two investigators. The profilometry readings reported higher surface roughness values for the control group when compared to the CS-NPs groups (p<0.001). However, no statistical significant difference was found between the two CS-NPs groups (p=0.72). Conclusion: CS-NPs exhibited bactericidal effect with no statistical difference between the two sizes. In addition, adhesive containing chitosan nanoparticles showed no effect on shear bond strength and exhibited lower surface roughness.