The remaining debris and biofilm in the anatomical complexities of root canal systems can affect treatment outcomes. Files with asymmetric cross-section design may improve debris and biofilm removal from these difficult spaces during canal preparation. Tooth opacity and different densities of the remaining materials prevent the direct systematic assessment of the preparation process. The present study assessed remaining debris and biofilm using a novel transparent root canal model with novel approaches. Natural and simulated root canal samples with isthmus space were evaluated. Canal preparation by ProTaper Next and Revo-S asymmetric systems was evaluated in comparison to the standard ProTaper Universal symmetric system. The root canals were investigated by microcomputed tomography (micro-CTL confocal laser scanning microscopy (CLSML and optical coherence tomography (OCT) imaging tools. Data analysis was undertaken with SPSS (V. 24). Files with asymmetric cross-section and constant taper removed more debris and biofilm from the complex root canal system. The model allowed direct assessment of remaining materials and confirmed the novel imaging approach with the OCT. In conclusion, the asymmetric design improves debris and biofilm removal especially when used with a constant taper. The model was verified as an ideal system for assessing root canal treatment in vitro
