(PO40) Evaluation of Nano-diamond Irrigants using Sonic and Ultrasonic Agitation Systems for Smear Layer and Hard-Tissue Debris Removal

Abstract: This study aimed to assess the effectiveness of nano-diamond irrigants agitated with sonic and ultrasonic instruments in removing both the smear layer and hard-tissue debris (HTD). Extracted single-rooted human teeth were instrumented using ProTaper Gold^® nickel-titanium rotary instruments (PTG). Subsequently, each canal was irrigated with 3% NaOCl, 17% EDTA, distilled water, and nano-diamond solutions (10–1000 nm). Sonic and ultrasonic instruments were compared for agitation. Scanning electron microscopy revealed that diamond solutions of 50 nm and above effectively removed the smear layer after 10 seconds of sonic agitation. Ultrasonic assistance with 500 nm and 1000 nm diamond solutions significantly outperformed other sizes in smear layer removal. In the second experiment, 40 mesial roots of human mandibular molars were selected based on 9-μm micro-computed tomography scans. Canals were mechanically prepared with PTG and divided into four groups (n=10): sonic agitation with nano-diamond solutions, sonic agitation with 17% EDTA, sonic agitation with 3% NaOCl, and conventional irrigation with NaOCl using a 30-G needle syringe. Post-preparation and post-final irrigation scans were collected, and data were analyzed for HTD percentage. The result showed sonic agitation with nano-diamond and 17% EDTA solutions achieved higher mean reductions of HTD (68.0% and 68.9%, respectively) compared to sonic agitation with 3% NaOCl and conventional NaOCl syringe irrigation (43.4% and 13.7%, respectively) (p < .05). These results demonstrated that sonic agitation with a nano-diamond irrigation solution can be an alternative approach for removing the smear layer and HTD in root canal treatment.