The effect of maintaining apical patency on canal transportation

AIM: To evaluate, ex vivo, the effect of maintaining apical patency on the original canal shape during preparation of curved roots by two different techniques. METHODOLOGY: Forty extracted human maxillary and mandibular molars were evaluated. Occlusal surfaces were ground and roots sectioned to the level of the cemento-enamel junction to allow only one root to remain for evaluation in each tooth. Specimens were divided into four experimental groups (10 canals each): Group 1--root canals prepared using the balanced force technique with stainless steel K-files, and patency established with size 10 K-files between each instrument; Group 2--same as Group 1 but without the use of a patency file; Group 3--canals instrumented with LightSpeed instruments and patency established with size 10 K-files between each instrument; and Group 4--same as Group 3 but without the use of a patency file. Specimens were mounted and a series of radiographs taken. Initial and post-preparation digital images were superimposed and the distance between two central axes at 1, 2 and 4 mm from the working length (WL) was measured to obtain an indication of the degree of apical transportation. Results were subjected to statistical analysis using two-way analysis of variance (ANOVA). RESULTS: No significant differences were found in degree of apical transportation at different levels of the root canal (P > 0.05) nor in loss of WL between groups (P > 0.05). CONCLUSION: In this laboratory study, maintaining apical patency did not influence canal transportation in the apical 4 mm.