Efficacy of Er,Cr:YSGG laser-activated irrigation with HEBP on smear layer and debris removal in the isthmus area of mandibular molars: A scanning electron microscopy and micro-computed tomography study

Objectives: To evaluate the effectiveness of Er,Cr:YSGG laser-activated irrigation combined with different final irrigants on smear layer and debris removal in the isthmus region of mandibular molars using scanning electron microscopy (SEM) and micro-computed tomography (micro-CT). Methods: Twenty extracted mandibular molars with confirmed isthmi on preoperative micro-CT were randomly allocated into four groups (n=5). After standardized canal preparation, final irrigation protocols included conventional needle irrigation with sodium hypochlorite and EDTA (control), laser activation with distilled water, laser activation with 17% EDTA, and laser activation with 18% HEBP. SEM images from isthmus regions were evaluated by blinded observers for smear layer and debris scores. Post-irrigation micro-CT scans were analyzed using 3D Slicer software to quantify hard tissue debris removal. Results: The HEBP group demonstrated the lowest smear layer and debris scores, followed by EDTA, distilled water, and control groups, with statistically significant intergroup differences (p < 0.05). Micro-CT analysis showed the highest percentage of hard tissue debris removal in the laser-activated HEBP group. Conclusions: Er,Cr:YSGG laser-activated irrigation combined with HEBP and EDTA significantly improves cleaning efficacy in the isthmus region compared to conventional irrigation. HEBP demonstrated effective debris removal with the potential advantage of reduced dentin erosion.