Abstract
INTRODUCTION: Eradication of residual biofilm from root canal dentine is critical for the success of regenerative endodontic procedures (REPs). THE AIM OF THE STUDY: To evaluate the influence of ultrasonically activated irrigants in concentrations used for REPs for removal of dual-species biofilm from three-dimensionally printed tooth models with attached dentine samples. METHODOLOGY: Seventy-two three-dimensionally printed teeth models were fabricated with a standardized slot in the apical third of the root to ensure a precise fit with a human root dentine specimen. Dual-species biofilms (comprising Enterococcus faecalis and Streptococcus mutans) were cultivated in the root canal for a period of three weeks. Models with dentine specimens were randomly assigned into 5 groups according to the irrigation protocol; G1(dis H2O): infected root canals irrigated with distilled water to serve as controls; G2(1.5% NaOCl): 1.5% NaOCl for five minutes; G3(1.5% NaOCl + PUI): 1.5% NaOCl + passive ultrasonic irrigation (PUI) for 30 s; G4(3% NaOCl): 3% NaOCl for five minutes; G5(3% NaOCl + PUI): 3% NaOCl + PUI for 30 s. Bacterial reduction was determined by colony-forming unit (CFU) counting (n = 12/G), whilst biofilms were analyzed using field emission scanning electron microscopy in additional samples. RESULTS: The four experimental groups showed a significant reduction in CFU counts compared to the control group (p < 0.05). When compared with (dis H2O), the highest reduction in bacterial count was obtained in G5 (3% NaOCl + PUI) followed by G4 (3% NaOCl), then G3 (1.5% NaOCl + PUI), and finally G2 (1.5% NaOCl). CONCLUSION: Results of the current study propose that a 3D-printed mature tooth model can be effectively used to analyze the antimicrobial effects of different irrigation protocols on dual-species biofilm. The use of NaOCl in concentrations used for regenerative endodontics can effectively remove bacterial biofilms. Furthermore, the use of PUI did not significantly enhance antibacterial effects of NaOCl.