Introduction: The aim of the present ex vivo research was to compare the remaining filling material and the volumes of dentine removed after retreatment of curved canals with two rotary systems naming ProTaper Universal Retreatment and Mani NRT-GPR using Micro-computed tomography (Micro-CT). Methods and Material: Forty mandibular molars containing two completely separated canals, with curvature angle of 25-35° and a curvature radius <10 mm were prepared to the Mtwo instrument 35/0. 04 and filled with warm gutta-percha and AH-Plus sealer. The teeth were randomly divided into 2 groups (n=20), according to the retreatment system evaluated: ProTaper Universal Retreatment (PR group) or Mani NRT-GPR (MR group). Retreatment was considered complete when the working length was reached and when smooth dentinal walls were observed, with no evidence of filling material adhered to instruments or in the irrigating solution. Preoperative and postoperative Micro-CT images were obtained with an isotropic voxel size of 11. 88 μ m to observe the volume of residual filling material in the canals and dentine removed after retreatment. Statistical analysis was performed by Student’ s t-test (P<0. 05). Results: The mean percentage of remaining filling material was 12. 96% for PR group and 24. 26% for MR group (P=0. 0056). The percentage of dentin removal was greater in the PR group (5. 02%) than MR group (1. 36%) (P=0. 0028). Both systems failed to completely remove the filling material from the canals. Conclusion: ProTaper Universal Retreatment system was more effective than Mani NRT-GPR system regarding removal of root filling material and also removed significantly more dentine after retreatment of curved mesial root canals of mandibular molars.

The routine measurement of direction-dependent reservoir rock properties like permeability often takes place along the axial direction of core samples. As permeability is a tensor property of porous materials, it should be fully described by a tensor matrix or by three main permeabilities in principal directions. Due to compaction, cementation, and other lithification processes, which take place after sedimentation, or later distortion and fractionation of the regional earth’ s crust, the axial direction of core samples, may not be always one of the main permeability directions. In this paper, a computational technique to find principal permeability directions from Micro-CT images of core samples was developed by us. Moreover, an assumed cube inside the core sample data with dimensions small enough to be able to imaginarily rotate inside the core limits has been chosen by us. Also, connected pore network was extracted from Micro-CT data, and permeability was calculated in all space directions. In addition, stepwise rotation process continued until all possible space directions were covered. Then calculated permeabilities from all directions have been compared with each other by us. Afterwards, maximum and minimum values have been found by us. In this paper, two Micro-CT datasets, which were taken from the Imperial College website, are used. Finally, the obtained results showed that the direction of maximum permeability within the carbonate core sample is about 30° deviation from the axial core direction. In addition to the main direction, the proposed computational technique can be effectively used to describe the permeability tensor of the reservoir rocks.

Prediction of porous media relative permeabilities from digital image data is of high demand nowadays when the power of the tomographic equipment is growing with an increasing order. In this work three phase relative permeabilities are estimated with co-applying Darcy’ s and Stokes equations in two case studies, namely Bentheimer sandstone and Estaillades limestone which their Micro-CT data files were downloaded from Imperial College website. In order to perform calculations firstly we extracted pore connected network from the Micro-CT data and it is estimated fluids distribution within pore channels during two-phase flow. Then we calculated pressure distribution of each phase solving its continuity and momentum equations within the obtained connected phase network. Pressure distribution and fixed volumetric flow rate ( that flows through all cross-sections perpendicular to the supposed flow direction), then were applied to solve for effective permeabilities. Effective permeabilities were then related to the relevant saturation and curves of two-phase relative permeabilities were derived in this manner. Stone’ s equation was finally applied to estimate three phase permeability ternary curves. Results showed that application of correlations for determining fluid distributions is accurate enough for multiphase relative permeability estimation in real case studies. This paper also shows that performing calculations on the segmented REVs is more accurate than work on simplified pore network models extracted from Micro-CT data.

Background: The background of this study was to improve the longevity of a restoration and optimal adaptation of restorative material to the prepared cavity walls is crucial. The study aimed to evaluate the interfacial adaptation of Activa, Micron, and Predicta bulk bioactive restorative materials to coronal dentin using Micro‑, computed tomography (CT) analysis. Materials and Methods: In this in vitro Micro‑, CT assessment study, Class II mesio‑,and disto‑, occlusal cavities were prepared on 60 extracted human mandibular molar teeth. After etching and bonding procedures, all the mesial cavities (n = 60) were restored with Tetric N‑, Ceram and the disto‑, occlusal cavities with Activa or Micron or Predicta bioactive (n = 20 each) restoratives. Interfacial gap percentages were evaluated under Micro‑, CT before (baseline) and after thermo‑, mechanical load cycling (TMC). Acquired data were analyzed statistically using one‑, way analysis of variance, Paired t‑, test, and Tukey’, s multiple post hoc procedures, at P < 0. 05 level of significance. Results: The interfacial gap percentages were lowest for Predicta bioactive and highest for the Micron group (P < 0. 05). The number of gaps increased significantly after TMC in all the groups (P < 0. 05). The adaptation of tested materials was inferior to axial wall and pulpal floor, whereas considerably better adaptation was observed on buccal and lingual walls. Conclusion: Predicta bioactive followed by Activa bioactive has shown superior interfacial adaptation, whereas Micron bioactive demonstrated maximum Microgaps compared to nanohybrid composite. Artificial aging with TMC has a negative influence on the internal adaptation of all tested materials.