Assessment of Antibacterial Effects of Chlorhexidine and Two Herbal Irrigants on Disinfecting Primary Tooth Root Canals Using Central Composite Design

Background: Primary endodontic infections are caused by necrotic colonization of the pulp tissues by microorganisms. The success of endodontic treatment depends on complete debridement and disinfection of the root canal space. Maximum antibacterial effects, maximum dissolving effects on necrotic tissues, and minimum toxic effects on the periapical tissues are essential characteristics of ideal root-canal irrigants. Recently, researchers have become further interested in medicinal plants as herbal medicines due to their good antimicrobial activities and natural origins. Objectives: This study aimed to compare the antimicrobial properties of chlorhexidine solution alone and mixed with two herbal solutions in root dentine and optimize factors affecting the disinfection of primary tooth root canals. Methods: Teeth infected with pure Enterococcus faecalis suspensions were treated with chlorhexidine solution alone and mixed with chamomile and Satureja khuzestanica. After selecting the most efficient solution, factors possibly affecting the disinfection process were optimized using a central composite design. These factors were the CHX concentration, chamomile concentration, and contact time. Results: The microbial colony count showed that the minimum colony count belonged to 1% chamomile essence and 1% CHX solution, while the maximum colony count belonged to 1% S. khuzestanica and 1% CHX solution, with significant differences. In the optimization process, the best chlorhexidine concentration, chamomile concentration, and contact time were 1.13%, 1.39%, and 11.33 min, respectively. Conclusions: A combination of chlorhexidine and chamomile provided protection against oral microbial pathogens for endodontic infections. However, further comprehensive in vivo studies seem necessary.