Evaluating the Impact of Ultrasonic Irrigation on Bacterial Levels and Activity Following Chemomechanical Procedures

This single-arm interventional trial aimed to investigate the efficacy of ultrasonic irrigation as a supplementary disinfection approach after chemomechanical procedures (CMP) using molecular techniques based on ribosomal RNA (rRNA) and rRNA genes (referred to as DNA).

Samples were collected from 35 single-rooted teeth with radiographic evidence of apical periodontitis. Samples were taken after gaining root canal access (S1), (S2), and ultrasonic irrigation (S3). DNA-targeted quantitative polymerase chain reaction using universal primers was used to estimate total bacterial levels, while rRNA-targeted quantitative polymerase chain reaction 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).

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.

Ultrasonic irrigation improved the disinfection of root canals after CMP by reducing bacterial levels. However, persisting bacteria remained active in the root canals after CMP and ultrasonic irrigation.