Background Endodontic success depends heavily on effective chemo-mechanical debridement of root canals through the use of instruments and irrigating solutions

Objective To compare the effectiveness of chamomile hydroalcoholic extract, BiopureTM mixture of tetracycline isomer, acid and detergent (MTAD) and 2.5 % sodium hypochlorite (NaOCl) on removal of the smear layer. Study design Randomised controlled trial

Methods Thirty extracted single-rooted, primary human teeth were allocated at random into three experimental groups of 10 teeth each. For each tooth, the canal was prepared using the step-back technique. During instrumentation, 2 ml of the irrigant was used for at least 10 s after each file and 10 ml as a final flush for 2 min for chamomile and NaOCL irrigants. Whereas for MTAD, an initial rinse with 1.3 % NaOCl for a cumulated period of 20 min, and use of MTAD as the final rinse for a period of 5 min was followed. Longitudinal grooves were made on root segments, then split into two halves with a chisel, stored in 2.5 % glutaraldehyde solution and fixed in ethanol series. Specimens were examined for the smear layer according to Hulsmann et al. (Int Endod J 35:668–679, 2002) criteria using a scanning electron microscope

Statistics Kruskal–Wallis and Mann–Whitney U tests were used

Results The most effective result in removal of smear layer occurred with the use of MTAD, followed by chamomile extract. The chamomile extract was found to be significantly more effective than 2.5 % NaOCl solution which had only minor effects

Conclusions The efficacy of chamomile to remove the smear layer was superior to 2.5 % NaOCl alone, but less effective than MTAD mixture