Bond strength of a calcium silicate-based sealer tested in bulk or with different main core materials

The aim of this study was to evaluate the influence of a calcium silicate-based sealer (iRoot SP), with or without a core material, on bond strength to radicular dentin, in comparison with various contemporary root filling systems. Root canals of freshly extracted single-rooted teeth (n = 60) were instrumented using rotary instruments. The roots were randomly assigned to one of the following experimental groups: (1) a calcium silicate-based sealer without a core material (bulk-fill); (2) a calcium silicate-based sealer + gutta-percha; (3) a calcium silicate-based sealer + Resilon; (4) a methacrylate resin-based sealer (RealSeal SE) + Resilon; (5) an epoxy resin-based sealer (AH Plus) + gutta-percha, and (6) a mineral trioxide aggregate-based endodontic sealer (MTA Fillapex) + gutta-percha. Four 1-mm-thick sections were obtained from the coronal aspect of each root (n = 40 slices/group). Push-out bond strength testing was performed at a cross-head speed of 1 mm/min, and the bond strength data were analyzed statistically by one-way analysis of variance and Tukey tests (p < 0.05). The highest and lowest debonding values were obtained for the calcium silicate-based sealer bulk-fill and mineral trioxide aggregate-based endodontic sealer + gutta-percha groups, respectively (p < 0.05). It was concluded that the calcium silicate-based sealer showed higher resistance to dislocation in the bulk-filled form than in conjunction with the tested core filling materials. When the calcium silicate-based sealer was placed in bulk, its dislocation resistance was similar to that of commonly used sealer + core root filling systems. Thus, the concept of using a calcium silicate-based sealer in bulk can be more easily advocated in clinical practice

Nonisothermal decomposition kinetics of trona

In the present work, experiments on the nonisothermal decomposition of trona in thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) devices were carried out, and kinetic analysis of the process was performed by employing four different approaches. It was determined that the process fits a first-order reaction kinetic model and that the value of the activation energy changes, to some degree, depending upon the method used in the analysis, with a maximum deviation of 8.9% from the average value. The activation energy was found to be approximately 112 kJ mol(-1), which is in good agreement with the data from similar studies in the literature

Dehydration kinetics of ulexite from thermogravimetric data

In the present study, the kinetic parameters of the thermal decomposition of ulexite were investigated by using TGA data. For the kinetic analysis, the Suzuki and Coats-Redfern methods were applied. It was determined that the process fits a first-order kinetic model, and the value of the activation energies and frequency factors decreased with decreasing particle size, which can be attributed to the increasing particle internal resistance to the escape of water as the grain size increases. The activation energy values were found to be 47.34-60.01 kJ mol(-1) for region I and 0.225-1.796 kT mol(-1) for region II for the range of particle size fraction used. The frequency factors were calculated to be 9821.8-524.9 s(-1) for region I and 3.05x10(-4)-2.807x10(-5) for region II for the same conditions

Thermal performance analysis for solid and perforated blocks attached on a fiat surface in duct flow

The thermal performances of solid and perforated rectangular blocks attached on a flat surface in a rectangular duct were determined with respect to the heat transfer from the same plate without blocks. The data used in the performance analyses were obtained experimentally for varying flow and geometrical conditions. It was found that the solid blocks generated a net energy loss despite significantly enhanced heat transfer due to the increased heat transfer surface area. When the blocks were perforated, the loss in the net energy was recovered and depending on the geometrical and flow conditions, a net gain in energy, up to 20%, was achieved. For both the solid and the perforated blocks, increases in Reynolds number led to decreases in the performance. (C) 2000 Elsevier Science Ltd. All rights reserved

FLASH DEHYDRATION OF ULEXITE AND INVESTIGATION OF DEHYDRATION KINETICS FROM THERMOGRAVIMETRIC DATA

The flash dehydration of a ulexite mineral in an entrained flow reactor was investigated. Flash dehydration experiments were carried out in the range 400-700 degrees C with material of particle size -425+300 mu m. The weight loss at 700 degrees C dehydration temperature was measured as 22%. A thermal gravimetric method was used to obtain the activation energy and rate constants for the dehydration of ulexite. The activation energy was in the range 48.2-53 kJ mol(-1) for different particle sizes. The rate constants for different particle sizes were found to vary between 1.8 x 10(-4) and 1.35 s(-1) in the temperature range 110-530 degrees C