Abstract: Objective：To compare the ability of four different root canal preparation methods on the oval-shaped root canal anatomy using 3-dimensional(3D) printing technology. Methods：An extracted maxillary second premolar with a single oval-shaped canal was selected and scanned with micro-computed tomographic imaging, and 80 replicas of the teeth were produced with a 3D printer. Replicas were assigned into 4 groups(n=20) and shaped with ProTaper systems (A); ProTaper systems and 20# H files (B); ProTaper systems and 25# H files (C); ProTaper systems and 30# H files(D) in a crown-down technique. Before and after root canal preparations, all samples were scanned by micro-computed tomography scanner and three-dimensional images were reconstructed. Images recorded were evaluated for morphometric measures regarding increase in canal volume, dentin removed, surface area and untouched walls. Statistical analysis of data was performed using One-way analysis of variance and LSD tests(P<0.05). Results：When comparing among groups, there was no significant difference regarding the volumes and surface areas before preparing root canals (P>0.05).Group C and group D showed more increases in canal volume and dentin removed than those in group A and group B (P<0.05). Group D had the most increase in surface area and the least percentage of untouched walls. (P<0.05). Conclusions：ProTaper NiTi instruments combined with large size H-files presented the best cleaning ability in the oval-shaped root canals.

Key words: oval-shaped canal, Root canal preparation, ProTaper NiTi instrument, H-file, 3-dimensional printing