Aim:To compare the smear layer and debris removal in root canals instrumented with two different kinematic motions after ultrasonic and sonic irrigation activation.Materials and Methods:Eighty freshly extracted teeth were selected for the study and randomly divided the samples into two groups (n = 40) for instrumentation with either rotary ProTaper NEXT (PTN) or reciprocating WaveOne (WO) file systems. These (n = 40) were further divided into two groups (n = 20) where the final irrigant was activated using either Ultrasonics (Passive Ultrasonic Irrigation; PUI) or Sonics (EndoActivator; EA). Group 1: PTN + EA; Group 2: PTN + PUI; Group 3: WO + EA; and Group 4: WO + PUI. During instrumentation, a total of 4 ml of 5.25% NaOCl was used for irrigation. The final irrigation protocol included NaOCl and Smear Clear Solution. The samples were processed by scanning electron microscopic examination for debris and smear layer scoring, and statistical analysis was done.Results:The mean debris and smear layer score was less in the group instrumented by PTN with sonic activation of the irrigant.Conclusion:A combination of PTN instrumentation with sonic irrigation activation by EA is more effective in debris and smear layer removal in the groups tested.

Aim:To compare the fracture resistance exhibited by teeth after primary endodontic treatment and retreatment.Materials and Methods:One hundred freshly extracted human teeth were selected. 20 samples served as control (untreated). Eighty experimental samples were divided into two groups (n = 40) for instrumentation using rotary Protaper NEXT (PTN) or reciprocating WaveOne (WO) files and obturated using warm lateral compaction. Half of the samples (n = 20) from each group were subjected to a load. The remaining half were subjected to retreatment using Protaper universal retreatment files (RFs) followed by a file larger than the master apical file used in groups 1 and 2 and reobturated. Group A: Control, Group B: PTN + obturation, Group C: WO + obturation, Group D: RF + PTN + obturation and Group E: RF + WO + obturation. The retreatment specimens were also subjected to load and the readings acquired were statistically analyzed.Result:When compared between the groups, control group exhibited the highest fracture resistance (P < 0.01). When multiple tests were performed, Group E exhibited significantly less fracture resistance (P < 0.01).Conclusion:Endodontic treatment and retreatment both results in lowering the fracture resistance of a tooth.