Evaluation of the removal of residual root canal filling material in extracted teeth by AutoCAD system following removal using different rotary retreatment kits.

Evaluation of the removal of residual root canal filling material in extracted teeth by AutoCAD system following removal using different rotary retreatment kits. Yeditepe University Institute of health sciences, Department of Endodontics, PhD thesis, İstanbul 2011.In some cases, root canal treatment may not be successful and retreatment is rendered necessary. The success of endodontic retreatment is dependent upon the removal of the previous root canal filling and sealer from the canal and successful cleaning and shaping.In the present study, 100 extracted teeth were used. The coronal parts were removed by separating discs to leave a root length of 15 mm. and working length was determined as 14 mm. The root canals were shaped by K file hand instruments (Dentsply Maillefer, Ballaigues, Switzerland) by the step back method.The root canals were filled by the vertical condensation method using continuous wave technique by Calamus Dual 3D Obturation System. The access cavities of the canals were filled temporarily with Coltosol F (Coltène/Whaledent AG, Switzerland). The teeth were stored in an incubator at 37 °C and 100% humidity, for two weeks to allow the sealer to set completely.After completion of root canal fillings, the experimental teeth were separeted into 5 groups. Root canal fillings ( guuta-percha+sealer) were removed using the following techniques.1. Group: R-Endo Retreatment System (Micro-Mega, Besancon, France)2. Group: ProTaper Universal Retreatment System (Dentsply Maillefer, Ballaigues, Switzerland)3. Group: D-RaCe Desobturation System (FKG DENTAIRE, La Chaux-de-Fonds, Switzerland)4. Group: Mtwo Retreatment System (VDW GmbH, Munich, Germany)5. Group: Headström Files (Dentsply Maillefer, Ballaigues, Switzerland)After the removal of root canal fillings, longitudinal grooves were opened on the buccal and palatinal surfaces with the help of a diamond separating disc mounted on a handpiece. The teeth were split longitudinally into 2 halves by the help of a spatula.The tooth halve?s images were placed under Leica DFC320 stereomicroscope and the canal surface images were transferred to the computer screen by Leica DFC Twain Software and were examined under X15 magnification. When the images obtained were clear, the photographs of the teeth were taken by Leica DFC Image Manager Software program. The tooth halves photographed by AutoCAD program were brought side by side and were decreased to the real tooth size. The canals were separated by three lines in the coronal, middle and apical regions. The internal borders of the canals were also drawn. The borders of the remnants of the filling material in the canal were drawn and the area was calculated as square millimeter (mm2), then, the percentage ratio of the remnant filling material in the canal was obtained by dividing the remnant filling material quantity in the canal (mm2) to the whole canal area (mm2) and then multiplying the result by 100. Also, the time to eliminate filling material was recorded by a chronometer. However, the time for irrigating the canals and the change of files were not added to this period.Statistical analysis was performed by ``NCSS(Number Cruncher Statistical System) 2007&PASS 2008?? Statistical Software (Utah, USA) program. Since the parameters were in compliance with the normal distribution when the study data were evaluated, ?Oneway Anova? test was used in the comparison between the parameter groups and ?Tukey HDS? test was used in determination of the group which caused the difference. The significance was evaluated at the level of p<0.05.Although the maximum amount of remnant filling material in the root canals retreated with R-Endo system was observed at the one third of the coronal region, there was no statistically significant difference between the apical, middle and coronal one third regions of the canal.Although the maximum amount of remnant filling material in the root canals retreated with ProTaper was observed at the one third of the coronal region, there was no statistically significant difference between the apical, middle and coronal one third regions of the canal.The maximum amount of remnant filling material in the root canals retreated with D-RaCe is seen at the one third of the coronal region, and there was statistically a high level of difference between the apical, middle and coronal one third regions of the canal.The maximum amount of remnant filling material in the root canals retreated with Mtwo-R was observed at the one third of the coronal region, and there was statistically significant difference between the apical, middle and coronal one third regions of the canal.Although the maximum amount of remnant filling material in the root canals retreated with Headström file was observed at the one third of the coronal region, there was no statistically significant difference between the apical, middle and coronal one third regions of the canal.When the amount of the remnant filling material in the canal was evaluated among the groups, the remnant filling material amount in all the groups except the Headström file group was seen at the maximum level in the coronal one third region when compared to the apical, middle and coronal one third region.When the time for removing the canal filling out of the canal was evaluated, there was statistically a high level of significant difference among the groups. Removal of the filling material by the Headström files required the longest period, followed by R- Endo, ProTaper, Mtwo-R and D-RaCe groups.None of the techniques were able to remove the canal filling material out of the canal completely. There was no statistically significant difference observed between the groups in terms of the quantity of the remnant canal filling material.Keywords: Retreatment, the remnant canal filling material, ProTaper Universal Retreatment, R-Endo, Mtwo R, D-RaCe, Headström hand file, AutoCAD.