In vivo evaluation of microbial reduction after chemo‐mechanical preparation of human root canals containing necrotic pulp tissue

Abstract

Aim To determine in vivo, the degree of microbial reduction after chemo‐mechanical preparation of human root canals containing necrotic pulp tissue when using two endodontic irrigating reagents, sodium hypochlorite (NaOCl) or chlorhexidine gel (CHX). Methodology Thirty‐two single rooted teeth with necrotic pulp were divided into two groups. One group (n = 16) was irrigated with 2.5% NaOCl, whilst the other group (n = 16) was irrigated with 2% CHX gel. Assessment of the bacterial load was accomplished by use of real‐time quantitative‐polymerase chain reaction (RTQ‐PCR) directed against the small subunit ribosomal DNA using the SYBRGreen and TaqMan formats. Statistical analysis was performed using the Mann–Whitney test. For contrast, bacterial load was also determined by traditional culture techniques. Results The bacterial load was reduced substantially in both groups (over 96%). However, using RTQ‐PCR the bacterial load before and after chemo‐mechanical preparation was greater when compared with evaluation using colony forming units (CFU). Furthermore, as measured by RTQ‐PCR, the bacterial reduction in the NaOCl‐group (SYBRGreen 99.99%; TaqMan: 99.63%) was significantly greater (P < 0.01) than in the CHX‐group (SYBRGreen 96.62%; TaqMan: 96.60%). According to culture technique 75% of cases were free of bacteria after chemo‐mechanical preparation in the NaOCl‐group, whilst 50% of cases were bacteria free in the CHX‐group. Conclusion NaOCl has not only a higher capacity to kill microorganisms but is also more able to remove cells from the root canal.