[ invitro study of the influence of [tug-back] on the apical seal in root canal therapy]

ABSTRACT

The final objective of root canal therapy is to create a complete seal along the length of the root canal system from the coronal opening to the apical termination and to accomplish the best adaptation from obturation material with canal walls. The tug-back of the master cone is recommended to provide apical seal. The purpose of this study, was to determine the influence of tug-back on the quality of the apical seal. In this experimental in vitro study, seventy single canal teeth were selected. The crowns were removed, the canals were prepared using a step-back instrumentation technique. Patency of the apical foramen was maintained and the teeth were divided into 2 experimental groups of 32. In the first group obtruration was achieved by tug-back in master cone and in the second group without tug-back using lateral condensation technique. Six teeth were used as control group, out of which three served as negative and three as positive controls. The teeth were placed in 100% humidity and 37 degree c for three days. The roots of the teeth were coated with two layers of nail varnish and one layer of stick wax except for the 2mm of apical end. Teeth were immersed in methylenblue 2% solution for one week and finally the teeth were sectioned vertically. The depth of maximum dye penetration for each tooth was recorded by two evaluators with stereomicroscope. All results were submitted for statistical analysis using Student's t-test. The mean linear dye penetration for experimental group with tug-back in master cone was 6.918 +/- 2.140 mm while this was 8.110+/-1.929mm in the group without tug-back. This difference was statistically significant [P=0.02]. The results of this study showed that the tug-back in master cone provided a significantly better apical seal