Comparing Streptococcus Mutans Adhesion by Using Different Orthodontic Bracket Ligations: An In Vitro Study

Introduction: Orthodontic treatments and brackets application with various ligature methods have increased worldwide, but the growth rate and mechanism of microorganism adhesion to these ligatures is not fully discovered. The current study aimed to compare the level of streptococcus mutans adhesion to three different ligation methods. Materials and Methods: This in vitro study was performed on 30 samples. Three different ligature methods were used and 10 samples were used in each group. In group A, conventional brackets with elastomeric ligature, in group B, conventional brackets with steel wire ligature and in group C, self-ligated brackets were used. Resin composite was condensed on the mesh surface of the brackets and cured for 40 seconds. Then, the coated samples with saliva were put into glass vials, immersed in 2 mL of streptococcus mutans suspension (×109 CFU) and incubated at 37ºC for 24 h. Then, the samples were washed 3 times with normal saline, immersed into 2 mL of normal saline and shaked for 2 min. The obtained suspension was cultured on blood agar incubated at 37ºC for 48 h and the formed colonies counted. In analysis, we performed 1-way analysis of variance with Tukey test with multiple comparison in SPSS version 16.  Results: According to the results, streptococcus mutans growth rate showed statistically significant differences in the three groups. It was minimum in the steel wire (23.80±1.40), and maximum in elastomeric ligatures (38.60±1.84). Conclusion: Steel wire ligatures had better effect on decreasing bacterial adhesion. The findings high light to decrease the use of elastomeric ligation brackets in patients with poor oral hygiene.