In vivo evaluation of microbial reduction after chemo-mechanical preparation of necrotic root canals with or without apical periodontitis

Objectives: Assessment of bacterial reduction after chemo-mechanical preparation (using3% sodium hypochlorite) with or without intracanal dressing (calcium hydroxide paste(Ca(OH)(2)) or 2% chlorhexidine digluconate gel (CHX)) in necrotic pulps associated or notwith apical lesion. Methods: Prospective clinical trial, in 69 adult patient's teeth with pulpal necrosis associated or not with apical periodontitis. Microbiological root-canal-sampling occurred before treatment (S1), after chemo-mechanical preparation (S2) and after 14 days intracanal dressing (S3). Colony Forming Units (CFU) were counted after growth in aerobic, anaerobic and microaerofilic cultures. Comparison of the median CFUs treatments and culture media was done with the Friedman test. Comparison of the intracanal dressing effect at S3 was done with the Wilcoxon and the Mann-Whitney tests. Because of the huge differences in bacterial counts variations were expressed as log 10 to analyze differences among intracanal medication groups. S2 and S3 counts were expressed as percentage of CFU reduction regarding S1 counts. Results: Significant differences were detected between S1, S2 and S3 (Friedman test; p < 0.001), showing a significant decrease from S1 to S2 (Wilcoxon test; p < 0.004), followed by a significant increase from S2 to S3 (p < 0.001) for the CHX group, maintenance for the Ca(OH)(2) group in aerobic/anaerobic (Wilcoxon test; p = 0.777/0.227), and increase in the microaerofilic culture (Wilcoxon test; p = 0.047). The two groups only differed significantly in S3 (Mann-Whitney test; p <= 0.001), with a worse performance in the CHX group. Conclusions: Treatment significantly reduced the number of bacteria but failed to render all root canals sterile. Ca(OH) 2performed better than CHX gel. (C) 2013 Sociedade Portuguesa de Estomatologia e Medicina Dentaria. Published by Elsevier Espana, S.L. All rights reserved.