Evaluation of smear layer removal using polymer and metal tips of ultrasonic irrigation device: an in vitro study

The aim of this study was to evaluate smear layer removal using a scanning electron microscope (SEM) following the use of 17% ethylenediaminetetraacetic acid (EDTA) and 5% sodium hypochlorite (NaOCl) irrigation solutions activated using metal-tipped and polymer-tipped irrigation devices in vitro. Sixty single-rooted mandibular premolars were prepared to a 15mm root length and assigned to three groups: conventional syringe irrigation (CSI), passive ultrasonic irrigation (PUI) with a polymer tip, and PUI with a metal tip. All canals were irrigated with 5% NaOCl and 17% EDTA, and ultrasonic activation was performed for 60 s with NaOCl and 30 s with EDTA in the PUI groups. Roots were longitudinally split, and smear layer removal in the coronal, middle, and apical thirds was evaluated under SEM by two blinded observers. Data were analyzed using the Kruskal–Wallis test and Dunn-Bonferroni test. Statistically significant differences were observed between irrigation methods across all regions (p < 0.001). The polymer tip was more effective for smear layer removal in the apical region than the metal tip (p < 0.001). Both the polymer and metal tips provided more successful results than the CSI in the coronal and mid-regions. In the apical region, only the polymer tip was statistically significantly more effective than CSI (p < 0.001). A polymer tip on a PUI device was more effective than a metal tip for smear layer removal, especially in the apical region.