RESUMO
AIM: This was to assess the antimicrobial effectiveness of pastes used as intracanal medicaments against Enterococcus faecalis in necrotic immature teeth. METHOD: An agar-disc diffusion method over a period of 30 days was used. The following medications were analysed: triple antibiotic paste (TAP) I; double antibiotic paste (DAP) I; DAP I with calcium hydroxide; calcium hydroxide paste with saline solution 0.9 %; calcium hydroxide paste with chlorhexidine 2 % gel; DAP II; DAP II with zinc oxide; DAP II with calcium hydroxide; and saline solution 0.9 % as control. The diameters of the halos of inhibition (in mm) of tested medicaments were determined and analysed with one-way analysis of variance and Tukey's post hoc tests. RESULTS: TAP I (G1) was significantly more effective against E. faecalis, and showed the largest halo of inhibition during all the experiments. DAP groups (G2 and G6) also showed inhibiting bacterial growth with said inhibition remaining stable throughout the 30-day period. In contrast, G4 and G5 groups, in which Ca(OH)2 was added to saline and chlorhexidine, had no antibacterial effect. CONCLUSIONS: TAP and DAP showed better antibacterial efficacy and remained active for 30 days. Combination of Ca(OH)2 with antibiotics should be avoided, due to the possibility of antibiotic hydrolysis.