The Effect of Using Patency File on Apical Transportation in Canals Prepared with Passive Step Back Technique

Abstract

Background: The purpose of this study was to assess the effect of patency file on apical transportation in curved canals prepared with passive step back (P.S.B) technique. Methods: This is an interceptive experimental, Invitro, study. Human extracted first permanent molars with 19-23mm length and curvature of 15-35 degrees (Schneider method) were considered for use in this study. Simple sampling was done and 35 teeth for each group was selected. In experimental group A canal preparation was done with P.S.B technique and usage of a # 10 file (as Patency file) between successive files. In experimental group B preparation was done in the same way except for usage of patency file. Pre and post operative radiographs were taken with similar condition. Radiographs were scanned and changes in canal curvature was determined using four different methods [Schneider, Weine, Long – Axis techniques (L. A.T), and Digital image overlay technique (overlay. T)] , using Idrisi for windows and AutoCAD softwares. Results: The mean of canal transportation angle in experimental group A with Schneider, Weine , LAT, and Over Lay techniques was: 7.006 ± 3.478, 12. 285 ± 6.032, 4.376 ± 3.516, 3.147 ± 2.744 respectively. Mean of canal transportation angle in experimental group B with the same methods was also determined: 8.009 ± 4.178, 13.55 ± 7.602, 9.464 ± 5.384, and 9.641 ± 5.382 respectively. T- test statistical analysis shows that there are no significant differences between the mean of canal transportation angles in two groups as measured by Schneider and Weine method (P>0.05). Mann- Whitney test shows that there are statistically significant differences between two groups as measured by LAT and Over Lay techniques (P<0.001). Conclusions: Results of this study shows that patency file in conjunction with P.S.B techniques causes significant reduction in apical transportation angle. Shortcomings of Schneider method in determination of canal curvature and specially assessment of apical transportation after instrumentation is mentioned in several studies. Our study shows that both Schneider and Weine techniques are not reliable methods for transportation assessment when compared with Image Over Lay technique. The result of LAT Shows close proximity with Over Lay technique and can be used for evaluation of apical transportation as a simple and reliable technique.
Keywords: Apical transportation, Passive step back, Apical patency, Schneider technique, Weine technique, Long axis technique,
OverLay technique.