Fig. 1

The representative 3-D models of round and oval canal in mandibular incisors. A Oval and round canal model before root canal preparation. B Oval and round canal after root canal preparation. C Matched and superimposed root canal indicated the untouched surface (red) and touched surface (green) from mesio-distal view. D Matched and superimposed root canal indicated the alteration of canal geometry after preparation, pre-operative canals (red) and the post-operative canals (green) from buccal-lingual view. E Cross-sectional views of the coronal, middle and apical thirds of before and after root canal preparation