Efficacy of irrigant activation techniques in removing intracanal smear layer and debris from mature permanent teeth: a systematic review and meta-analysis

Aims: To establish whether irrigant activation techniques (IATs) result in greater intracanal smear layer and debris removal than conventional needle irrigation (CNI). Methodology: Six electronic databases were searched to identify scanning electron microscopy studies evaluating smear layer and/or debris removal following the use of manual dynamic activation (MDA), passive ultrasonic irrigation (PUI), sonic irrigation (SI) or apical negative pressure (ANP) IATs in mature permanent teeth. Meta‐analyses were performed for each canal segment (coronal, middle, apical and apical 1 mm) in addition to subgroup analyses for individual IATs with respect to CNI. Outcomes were presented as standardized mean differences (SMD) alongside 95% confidence intervals (95% CI) and chi‐squared analysis. Results: From 252 citations, 16 studies were identified. The meta‐analyses demonstrated significant improvements in coronal (SMD: 1.15, 95% CI: 0.72–1.57 / SMD: 0.54, 95% CI: 0.29–0.80), middle (SMD: 1.30, 95% CI: 0.59–2.53 / SMD: 0.8, 95% CI: 0.58–1.13) and apical thirds (SMD: 1.22, 95% CI: 0.83–1.62 / SMD: 1.86, 95% CI: 0.76–2.96) for smear layer and debris removal, respectively. In the apical 1 mm IATs improved cleanliness; however, differences were insignificant (SMD: 1.15, 95% CI: ‐0.47–2.77). Chi‐squared analysis revealed heterogeneity scores of 79.3–92.8% and 0.0–93.5% for smear layer and debris removal, respectively. Conclusions: IATs improve intracanal cleanliness across a substantial portion of the canal, and therefore, their use is recommended throughout root canal preparation. However, current data is too heterogeneous to compare and identify superiority of an individual technique highlighting the need to standardize experimental protocols and develop a more representative research model to investigate the in vivo impact of IATs on clinical outcomes and periapical healing following root canal treatment.