Experimental model of infection by Enterococcus faecalis biofilms in human root canal and dentinal tubules.

GABRIELA MARTIN, GIULIANA MOSCONI, OMAR GANI, MARKUS HAAPASALO, CARMEN VISVISIÁN, MARÍA G PARAJE.

Rosario

Congreso; X Congreso Argentino de Microbiología General (SAMIGE); 2013

SAMIGE

Root canal irrigations is considered as an important step during endodontic therapy, for cleaning, removal of debris and for its antimicrobial action. Sodium Hypochlorite (NaOCl ) is the most common irrigating solution used during chemo-mechanical preparation, not only because it solves organic components but also for its antibacterial properties. The aim of the present study was to evaluate an experimental model for biofilms infection of human root canals and dentinal tubules with Enterococcus faecalis and compare the antibacterial effect of different solutions. 80 freshly extracted intact human premolars distributed into 4 groups of 20 teeth each were used. Group A: 14 to 25 year-old and Group B: older than 50 year-old. Each one was divided into two subgroups (A1, A2, B1, and B2). The subgroups 2 were irrigated with sterile saline solution. After an appropriate preparation were infected with E. faecalis (ATCC29212) and incubated for 45 days at 37ºC. To confirm the biofilm formation, 2 teeth of each group were selected randomly to be evaluated by confocal laser scanning microscopy (CLSM) and scanning electron microscope (SEM). Following this incubation, the premolars (A1 and B1) were instrumented with ProTaper system and irrigated with NaOCl 1%[1]; 2.5%[2]; or 5%[3]; MTAD (Doxycycline-Tween 80-Citric acid)[4] or iodine potassium iodide solution (IPI). Two bacteriologic samples were taken from the root canal: the first one before instrumentation and irrigation, and the second one after the final irrigation. The samples, followed by serial dilutions, were plated and incubated at 37ºC for 48 hs, 7 and 30 days. The colony forming units (CFU/ml) grown were counted. The E. faecalis biofilms development was evident in the root canals of groups observed by CLSM and SEM. Bacterial populations were slightly higher in group A1 (8,8x 1010 CFU) compared with group B1 (8,3x 1010 CFU), but this difference reached no statistical significance (P=0.1). The intergroup analyses evaluating the reduction of E. faecalis with NaOCl, MTAD and IPI demonstrated that the frequency of negative cultures was of 71% for IPI, 50 % for MTAD and 5% NaOCl; and 42.9% for 1 or 2.5% NaOCl. Immediately after of the instrumentation and irrigation, with all irrigating decreased the number of CFU. At 2 days continued to decline slightly in groups 1 and 3, and markedly in 5, while increased by 2 and 4. At 7 days, continued decline in 1, showing a slight increase in the other groups. At 28 days remained stable the biofilms development in 4 and 5 and observed a slight increase in 1, 2 and 3. The model was suitable for biofilm infections of root canal and dentin in all age groups. During instrumentation and the final irrigation with an antimicrobial agent, disinfection of the root canal increased. IPI was the most effective irrigating solution, followed by MTAD and 5%NaOCl. However, in all cases there was a reinfection, which is a hallmark of infections