INTRODUCTION:Minimally invasive endodontics (MIE) is the latest innovation in endodontics that focuses on minimal mechanical preparation; as it leads to preserving the fracture strength of teeth. AIM OF THE STUDY:To compare the fracture resistance of mandibular molars following preparation by TruNatomy versus ProTaper Next rotary instruments. MATERIALS AND METHODS: Thirty permanent mandibular molars were selected in this study. Teeth were randomly distributed into two equal groups. Decoronation of the crown was done and the distal root was sectioned from the mesial root and acted as a control group. Study Group I: Fifteen mesial roots (MB and ML canals) were prepared using TruNatomy (TRN) rotary files up to the prime file (26/.04). Study Group II: Fifteen mesial roots were prepared using ProTaper Next (PTN) rotary files to size X3(30/.07). Control Group: The distal root of each tooth. Roots were placed in acrylic resin blocks and fracture loading was applied. Data were statistically analyzed. RESULTS: Roots prepared with TRN were significantly more fracture resistant than roots prepared with PTN. In addition, a significant difference was noted between the mesial and distal roots within each group. CONCLUSIONS: Mandibular molar mesial roots prepared with TRN rotary files (26/.04) are significantly more fracture resistant than those prepared with PTN rotary files (30/.07). In addition, intact mandibular molar distal roots were significantly less prone to fracture than the mesial roots prepared with both systems.

INTRODUCTION:Removal of initial endodontic filling material during retreatment is mandatory for favorable outcomes. OBJECTIVES: This study aimed to assess the influence of chloroform and passive ultrasonic irrigation (PUI) on the retrieval of endodontic filling material during retreatment using CBCT for evaluation. METHODS: Forty extracted single canaled lower premolars were decoronated, instrumented with ProTaper Next files (X3), and filled with lateral condensation technique. Samples were randomly distributed into two groups with further subdivision into four subgroups according to the use of chloroform and PUI as follows: Group A1 (chloroform/PUI), Group A2 (chloroform /without PUI), Group B1 (without chloroform/PUI), Group B2 (negative control) (without chloroform / without PUI). Retreatment was done with ProTaper Universal retreatment (PTU) files in all teeth. Before and after-retreatment CBCT-scans were done for all samples, and the residual volumes were measured. Statistical analysis was performed with a level of significance set at a P-value of 0.05. RESULTS: Complete removal of endodontic filling material was not achieved by any tested techniques. However, the negative control group (B2) showed the least mean percentage of residual volume (5.95%), while chloroform with the PUI group (A1) showed the greatest mean percentage of the residual volume (17.98%), with no significant difference between the four study groups. The greatest mean residual volume was revealed at the coronal third in all study groups. CONCLUSION: PTU-file without chloroform and PUI was the most effective in removing endodontic filling material.

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BACKGROUND: Calcium hydroxide (Ca(OH)2) is the most currently used intracanal medicament. Its remnants within the root canal have been found to negatively impact the final obturation. Accordingly, its complete removal is critical. OBJECTIVES: This study aimed to compare the removal of Ca(OH)2 paste from root canals using passive ultrasonic irrigation, EDDY sonic activation, Roeko canal brush and manual filing, using cone beam computed tomography (CBCT) for evaluation. METHODS: Forty single canaled extracted human teeth were prepared using ProTaper Next files (X3) and filled with Ca(OH)2 paste. The teeth were assigned randomly to four groups of 10, based on the method of Ca(OH)2 removal: Group A: Passive ultrasonic irrigation (PUI), Group B: EDDY sonic activation, Group C: Roeko canal brush and Group D: manual filing (Control group). Samples were scanned with CBCT and the intracanal Ca(OH)2 volume was measured pre and post retrieval. Statistical analysis was performed using Kruskal Wallis test followed by Bonferroni correction, with a level of significance set at P value of 0.05. RESULTS: Complete removal of intracanal Ca(OH)2 was not achieved by any of the tested techniques. However, PUI and EDDY removed a mean of (99.89% ± 0.19) and (99.86% ±0.34) of the intracanal paste, respectively, with no statistically significant difference between them. The apical third demonstrated the largest volume of residual paste. There was a statistically significant difference when PUI and EDDY were compared to the control group (p <0.0001). CONCLUSION: PUI and EDDY are the most effective methods in removing intracanal calcium hydroxide.