Introduction: Surgical endodontic treatment comprises of thorough debridement of pathological periradicular tissue, root end resection followed by a Class I retrograde cavity preparation and insertion of root end filling material into the prepared cavity. The aim of this study was to evaluate the push out bond strength of Biodentine, Mineral Trioxide Aggregate (MTA) and Bone Cement used in the retro cavities, prepared with ultrasonic retro tips. Material and methods: 60 human extracted single rooted teeth were selected and sectioned with a diamond disc (Horico, Germany) to standardize the root length of 15mm. The roots were instrumented with rotary ProTaper Universal (Dentsply Maillefer) system till size F2. The root canals were obturated using gutta percha (Dentsply, Maillefer) and AH Plus sealer (Dentsply, Germany). 3mm of root end resection was performed with high speed hand piece under water coolant. 3mm deep retro cavities were prepared with ultrasonic stainless steel retro tip (Woodpecker). All the specimens were divided into 3 groups (n=20) Group I: MTA (ProRoot, Tulsa Dental, USA), Group II Biodentine (Septodont, France), Group III Bone Cement (Depuy, Johnsons and Johnsons). Each material was mixed according to the manufacturers instructions and filled into the retro cavities. The specimens were sectioned perpendicularly to obtain 1mm thick slices from the apical portion and subjected to push out bond strength testing under Universal Testing Machine (Instron). Results: Biodentine showed more push out bond strength than MTA and Bone Cement. There was no significant difference between MTA and Bone Cement groups. Conclusion: Bone Cement can be considered as one of the potential retro filling material.

Introduction: Biomechanical preparation of root canals is one of the main steps in achieving endodontic success due to enabling bacterial elimination, removal of debris, and facilitating obturation. The aim of this study was to compare the incidence of dentinal cracks observed in the canal wall after canal instrumentation with 3 single-file systems and the ProTaper system (Dentsply Maillefer, Switzerland). Material and Methods: Eighty mandibular premolars with single root canal were selected. Teeth were decoronated and mounted in resin blocks with simulated periodontal ligaments. They were divided into 4 experimental groups (n = 20); then instrumented to the full working length with the ProTaper, OneShape (MicroMega, Besancon, France), Reciproc (VDW, Munich, Germany), and WaveOne Gold (Dentsply Malliefer) was performed. The roots were sectioned perpendicular to the long axis at 3, 6, and 9 mm from the apex and were observed under a stereomicroscope. The presence of cracks was noted. The chi-square test was performed to compare the appearance of cracked roots between the experimental groups. Results: Cracks found after canal instrumentation with the ProTaper, OneShape, and Reciproc and WaveOne Gold files, were 46.6%, 23.3%, 13.6%, 11.6% respectively. The difference between the experimental groups was statistically significant (P < .001). Conclusion: Nickel-titanium instruments cause cracks in root surface or in the canal wall; Reciproc and WaveOne Gold files caused less cracks than the ProTaper and OneShape files.