Objective: The aim of this study was to investigate the effects of two different self-adjusting file (SAF) working times and three different chelating agents on the push-out bond strength of root canal fillings in oval root canals. Materials and Methods: Eighty mandibular premolars were selected and distributed into 8 groups (n=10): 4 min SAF (G1), 4 min SAF + 17% ethylenediaminetetraacetic acid (EDTA) (G2), 4 min SAF + 10% citric acid (CA) (G3), 4 min SAF + 1% peracetic acid (PAA) (G4), 6 min SAF (G5), 6 min SAF + 17% EDTA (G6), 6 min SAF + 10% CA (G7), and 6 min SAF + 1% PAA (G8). The root canals were filled using guttapercha and AH Plus root canal sealer, and the teeth were prepared for the push-out assessments using 1.0 mm thick root slices. Loading was performed with a universal testing machine at a speed of 0.5 mm/min; and then, collected data were analyzed statistically (α=0.05). Results: While the different chelating agents significantly affected the push-out bond strength of the root canal filling (p<0.05), the different SAF working times did not (p>0.05). There were no significant differences among the groups in the apical and middle thirds of the roots (p>0.05). In the coronal thirds, G6 and G8 indicated significantly greater bond strength values than G1 and G5 (p<0.05). Conclusion: According to the results, the 4 and 6 min SAF working times did not affect the bond strength of the root canal filling. PAA and EDTA can be recommended for root canal irrigation after SAF usage.

The aim of this study was to evaluate the forces required to fracture roots obturated with different calcium silicatebased materials, after applying a fractured instrument removal simulation. Material and Methods: Seventy-five mandibular premolars were selected and decoronated. Then, all root canals were instrumented using Reciproc system. To mimic the root canal anatomy after the removal of a fractured instrument, each canal was enlarged with a size-3 Peeso reamer. The specimens were distributed into experimental groups according to the materials used for the root fortification: G1: Negative control, G2: ProRoot MTA, G3: Ortho MTA, G4: Biodentine, G5: Endocem MTA. Then, the teeth were embedded into acrylic blocks. A vertical fracture test was applied, and the fracture loads were recorded. Statistical interpretations were made (α=0.05). Results: G2, G3, G4, and G5 showed greater fracture resistances than G1 (p<0.05). There was no significant difference among G2, G3, G4, and G5 (p>0.05). Conclusions: Any of the tested materials could be chosen to reinforce the root after the removal of a fractured instrument.

Aim: The aim was to evaluate the effects of antioxidant application and delayed cementation on the bond strength of fiber posts after intracoronal bleaching. Methodology: Fifty-five maxillary central incisors were used. Root canals were enlarged using Reciproc system up to R40 instrument. Root canals were irrigated, dried with paper-points, and obturated with gutta-percha and a sealer. In 44 teeth, root canal fillings were removed 2-mm coronally and canal orifices were sealed with glassionomer-cement. A 37% carbamide peroxide (CP) gel was used to bleach the teeth. Five experimental groups were defined (n=11). G1: No bleaching, G2: Immediate fiber post cementation (FPC), G3: Immediate FPC after sodium ascorbate (SA) application, G4: 14-days delayed FPC, G5: 14-days delayed FPC after SA application. Push-out tests were performed. Statistical interpretations were made (α=0.05). Results: There was no significant difference among the groups in apical thirds (p>0.05). However, significant differences were detected among the groups in middle and coronal thirds (p<0.05). Conclusions: The 14-days delayed cementation seems to be a more reliable method than the SA application before FPC procedure after intracoronal bleaching.