The effect of maintaining apical patency on canal transportation

To evaluate, ex vivo, the effect of maintaining apical patency on the original canal shape during preparation of curved roots by two different techniques.

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).

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).

In this laboratory study, maintaining apical patency did not influence canal transportation in the apical 4 mm.