Evaluation of the effect of different staging platform preparation and instrument removal techniques on broken instrument removal from root canal and fracture strength of teeth

The aim of this study is to evaluate the effectiveness of preparation different staging platforms to access the broken instrument, partial or full dentin removal at the coronal and around the broken instrument and removal of broken instrument using ultrasonic tips or BTR Pen and to examine the effect of these methods on the fracture strength of teeth. The crowns of 100 extracted human teeth of similar size were removed and the root canals were shaped with #15 and #20 K-type hand files. The samples were randomly divided into 1 control (n=10) and 6 experimental groups (n=15). A 25.06 rotary file was broken at a length of 4 mm in the middle third region of the canal in the experimental groups. Access to the broken instrument was performed with Gates Glidden burs or ultrasonic tips. Then, dentin was removed from the coronal and surrounding areas of the broken instrument to create partial or full platforms. Finally, the broken instruments were removed from the canals with ultrasonic tips or BTR Pen. The effectiveness of broken instrument removal, duration of removal, and the complications occurred were recorded. All root canals were filled with cold lateral condensation technique. Fracture strength analysis was performed using a universal testing machine. Data were analyzed statistically with Kruskal Wallis and Games-Howell tests (p=0.05). Although in some samples the broken instruments were pushed apically and, secondary instrument fractures and root canal transportation occurred, all broken instruments in the groups were successfully removed from the canals. In general, access time to the broken instrument in the groups using Gates Glidden burs were shorter than in the groups using ultrasonic tips (p<0.05), while there was no significant difference in the total instrument removal time between the groups (p>0.05). The control group showed similar fracture strength to the group in which ultrasonic tips and BTR Pen were used (p>0.05), and showed higher fracture strength than the other experimental groups (p<0.05). In conclusion, accessing the broken instrument with ultrasonic tips, creating a full platform and removing the broken instrument from the canal using BTR Pen can be recommended for clinical applications. Keywords: Broken file, BTR Pen, Lasso&Anchor technique, Staging platform, Ultrasonic