Minimally Invasive Root Canal Cleaning: Evaluating Supplementary Irrigation Techniques

<b>Objectives:</b> This study aimed to evaluate the efficacy of cleaning in minimally shaped mesial and oval distal canals of 3D models of mandibular molars, focusing on positive pressure irrigation, wireless and conventional passive ultrasonic irrigation (PUI), and diode laser (DL) at 980 nm. <b>Methods:</b> Forty-four 3D-printed resin models, based on eleven natural mandibular molars (each with mesial and distal canals), were divided into four groups (<i>n</i> = 11 per group) to evaluate different irrigation methods. A total of 22 mesial canals (size 20/.04) and 11 oval distal canals (size 25/.04) were analyzed per group. Each root canal was uniformly filled with an artificial hydrogel to simulate a biofilm mixture. Following this preparation, the specified irrigation techniques were applied to the respective groups. Quantitative evaluations of pre- and post-irrigation images were performed to assess the efficiency of tissue removal along the entire length of the canal and in the apical, middle, and coronal thirds. <b>Results:</b> The findings revealed no significant differences in the initial amount of tissue between the samples, indicating uniform filling. In the apical region of mesial canals, conventional PUI showed the highest cleaning efficiency (14.1% residual tissue), significantly outperforming the other methods (<i>p</i> < 0.05). Cordless PUI and DL also surpassed positive pressure irrigation, leaving 30.4% and 29.3% residual tissue, respectively, compared to 42.2% with positive pressure. In the middle third, all methods tested performed better than needle irrigation (<i>p</i> < 0.05), but there were no significant differences in the coronal third or over the full canal length. Distal oval canals showed no significant differences in cleaning effectiveness among methods. <b>Conclusions:</b> Although no single method was superior regarding the full canal length, supplementary techniques such as PUI and DL offer potential benefits over conventional irrigation methods, particularly in the apical third of the canal. Complementary approaches such as conventional PUI and diode laser at 980 nm showed superior cleaning efficiency, particularly in the apical third. These results suggest their integration could improve the effectiveness of cleaning in minimally instrumented mesial canals.