Antimicrobial effect of chlorhexidine on Aggregatibacter actinomycetemcomitans biofilms associated with peri-implantitis

Background. This study aimed to assessthe antimicrobial effect of chlorhexidine (CHX) on Aggregatibacter actinomyce-temcomitans biofilms isolated from subgingival plaque of peri-implantitis lesions. Methods. Thirteen patients requiring peri-implantitis treatment were consecutively selected and their subgingival biofilm was collected by inserting fine sterile paper points into peri-implant pockets for 15 seconds. A. actinomycetemcomitans was isolated from the subgingival biofilm and cultured. In this study, the standard strain of A. actinomycetemcomitans served as the positive control group and a blank disc impregnated with water served as the negative control; 0.1 mL of the bacterial suspension was cultured on specific culture medium and blank discs (6 mm in diameter) impregnated with 0.2%CHX mouthrinse (Behsa Pharmaceutical Co.) and negative control discs were placed on two sides of the bacterial culture plate. The size of growth inhibition zone was measured by a blinded independent observer in millimetres. Results. According to the results of disc diffusion test, the mean diameter of growth inhibition zone of A. actinomycetem-comitans around discs impregnated with CHX was larger in both standard (positive control) and biofilm samples of A. acti-nomycetemcomitans compared to the negative control group (blank disc) (P<0.001). Conclusion. Use of0.2% CHX mouthwash had antibacterial effects on A. actinomycetemcomitans species isolated from peri-implantitis sites.