RESUMEN

AIM: This single-arm interventional trial aimed to investigate the efficacy of ultrasonic irrigation as a supplementary disinfection approach after chemomechanical procedures using molecular techniques based on ribosomal RNA (rRNA) and rRNA genes (referred to as DNA). METHODOLOGY: Samples were collected from 35 single-rooted teeth with radiographic evidence of apical periodontitis. Samples were taken after gaining root canal access (S1), chemomechanical procedures (CMP, S2), and ultrasonic irrigation (S3). DNA-targeted qPCR using universal primers was used to estimate total bacterial levels, while rRNA-targeted qPCR was used to assess bacterial activity. Ratios between rRNA and DNA levels were calculated to search for active bacteria in the samples (rRNA/ DNA ≥ 1). Wilcoxon matched-pairs signed-rank test was used to compare the differences in DNA levels between samples and DNA and rRNA levels within samples (P <.05). RESULTS: DNA-based methods revealed a significant decrease in bacterial levels from S1 to S2 and S2 to S3 (both P <.05). Notably, 11 out of 35 (31.4%) root canals did not harbor bacterial DNA after CMP, whereas ultrasonic activation increased DNA-negative samples to 17 (48.6%). However, all DNA-positive samples were also positive for rRNA, with significantly higher rRNA than DNA levels (P <.05), indicating bacterial activity at the sampling time. CONCLUSIONS: Ultrasonic irrigation improved the disinfection of root canals after chemomechanical procedures by reducing bacterial levels. However, persisting bacteria remained active in the root canals after CMP and ultrasonic irrigation.