Effect of apical preparation size on bacterial reduction within root canals in vivo and in vitro

Abstract

OBJECTIVES: To determine if increasing the apical preparation size significantly reduces bacterial counts in vivo and in vitro. METHODS: In vivo DNA extraction was performed from samples of single rooted teeth (n=50) with necrotic pulps (first sample, S1) and after instrumentation to an apical size of 35/.04 (S2) and 50/.04 (S3). Analysis of total bacteria and that of Streptococci was done using real-time polymerase chain reaction. For the in vitro experimentation, root canals (n=45) with biofilms of Enterococcus faecalis were instrumented similar to the in vivo model (n=15 per group) and sampled. Untreated teeth served as control. Percentage of live/dead bacteria within the root canal lumen and dentinal tubules was determined using confocal laser scanning microscopy. Results were compared using Mann-Whitney U test (in vivo) and one-way ANOVA (in vitro). RESULTS: Compared to the control, S2 and S3 showed significant bacterial reduction (P0.05). The in vitro results were similar to the in vivo result for samples obtained from the root canal lumen, but not within the dentinal tubules, which showed significantly more dead bacteria for S3, compared to S1 or S2 (p