Physico-Chemical Properties of Calcium-Silicate vs. Resin Based Sealers—A Systematic Review and Meta-Analysis of Laboratory-Based Studies

Introduction: The aim of this systematic review is to analyse the effect of physico-chemical properties of calcium silicate-based sealers in comparison to epoxy resin sealers in permanent teeth using a single-cone obturation technique. Methods: The study was conducted according to the guidelines of Cochrane Handbook for Systematic Reviews of Interventions and Preferred Reporting Items for Systematic Review and Meta-Analyses (PRISMA) statement. Literature search was performed using the PubMed/MEDLINE, Cochrane Central Register of Controlled Trials, Web of Science, DOAJ, Open Gray with no language restrictions until October 2020. Two reviewers assessed the studies for eligibility. Grading of Recommendations, Assessment, Development, and Evaluations (GRADE) was carried out to assess the evidence. Meta-analysis of the pooled data with subgroups was performed using the RevMan software (p < 0.05). Results: Results from the 28 included studies showed that the mean difference in adaptation to root canal walls (marginal adaptation, interfacial gaps and void volume) for both sealers were non-significant. However, void volume values showed a significant mean difference (p < 0.00001) favouring the calcium silicate-based sealers. The pooled meta-analysis reported statistically significant differences for apical microleakage (p = 0.0007) whilst there were non-significant mean differences for fracture resistance (p = 0.09) and push-out bond strength (p = 0.63). The heterogeneity among the included studies was 97% (I2). Conclusions: Within the limitations of this review, calcium silicate-based sealers demonstrated a similar or superior performance in comparison to resin-based sealers in terms of the physico-chemical properties.

Comparison of Obturation Quality between Calcium Silicate-Based Sealers and Resin-Based Sealers for Endodontic Re-treatment

Background: The objective of this micro-computed tomography (micro-CT)-based study was to compare the filling quality of endodontic treatment and endodontic Re-treatment between two sealers with matched obturation techniques: calcium silicate-based sealer (Endoseal TCS) with a single-cone technique (SCT) and resin-based sealer (AH Plus) with a continuous wave technique (CWT). Methods: Forty maxillary premolars were selected and assigned into four groups, according to the obturation methods of the first endodontic treatment and Re-treatment (n = 10). The AP/AP group was first treated with AH Plus/CWT, then re-treated with AH Plus/CWT. The AP/ET group was first treated with AH Plus/CWT, then re-treated with Endoseal TCS/SCT. The ET/AP group was first treated with Endoseal TCS/SCT, then re-treated with AH Plus/CWT, and the ET/ET group was first treated with Endoseal TCS/SCT, then re-treated with Endoseal TCS/SCT. The specimens were scanned using micro-CT at three time points: after the first endodontic treatment, after gutta-percha (GP) cone removal, and after Re-treatment. The void volume of root canal obturation and the volume of the remaining filling materials were calculated. Data were analyzed using Student’s t-tests and ANOVA. Results: The Endoseal TCS groups (ET/AP and ET/ET) showed a lower percentage of voids than the AH plus groups (AP/AP and AP/ET) on the whole canal and the apical third, after first obturation (p < 0.05). The AH plus group showed significantly fewer remnants than the Endoseal TCS group after GP removal (p < 0.05). Re-treated canals and initially treated canals had similar void volumes (p > 0.05). There was no significant difference in void volume after Re-treatment, regardless of whether the same or different sealers were used for the first treatment and Re-treatment (p < 0.05). Conclusions: Endoseal TCS sealer and AH Plus sealer had a similar Re-treatment efficacy, regardless of which sealer was used in the previous treatment.

THE ANALYSIS OF ADMISSIBLE LEVEL OF FORMALDEHYDE IN AIR

By production of glued and plate wood-base materials with use of carboamidoformaldehyde pitches (KFS) the main lack of technology of which is toxicity of these materials to the person. Toxicity is caused by allocation from these materials of gas, harmful to the person, - formaldehyde which is cancerogenic substance. Wood-shaving plates from needle (DSTP) and large-size shaving (OSB), fiber boards (DVP) including the Intermediate-density fiberboard (MDF), and also plywood of general purpose and different types of special plywood (decorative, bakelized, etc.), first of all, belong to such materials. The Russian Ministry of Health has established very strict requirements on release of formaldehyde in air both in premises, and in free air the admissible level of which makes (DU) only 0,01 mg/m3 of air when testing materials by chamber method. The plate materials released now can exceed DU of 17 times stated above. Especially it concerns DSTP. Despite attempts of institute Vniidrev through appeals to relevant authorities of the Ministry of Health to increase such admissible level in our country, generally for plate materials, were not crowned with success yet and this level in real time remains in force. It is possible to use such plates in premises only at very small saturation them room void volume (the saturation is defined as the relation of surface area of plates indoors to room void volume). So, by our researches for example it is proved that the written dvukhtumbovy table made of DSTP of class of release of formaldehyde E2 can be established in living room of 20 sq.m only one and no more. Only in this case, at small saturation room void volume plates, the release of formaldehyde in air of the room will meet requirements of domestic DU. In premises the case furniture is in reality with much bigger saturation that leads to room gas contamination formaldehyde. In too time abroad formaldehyde size DU in air much more also makes 0,124 mg/m3 of air. In this regard the purpose of our work consisted in the analysis of DU of formaldehyde in air of foreign researches.

SATURATION RESEARCH MAKSIMALNY BY WOOD-SHAVING PLATES OF PREMISES

The wood-shaving plates (DSTP) released by the domestic industry with use of carboamidoformaldehyde pitches (KFS) have very essential shortcoming connected with their toxicity because of considerable allocation from them gas, harmful to the person, - formaldehyde. In recent years formaldehyde is recognized as substance, cancerogenic for the person. It concerns different type of plates: from needle (DSTP) and large-size shaving (OSB), fiber boards (DVP), including medium-density DP-SP (or MDF). The Russian Ministry of Health has established very strict requirements on release of formaldehyde in air both in premises, and in free air the admissible level of which (DU and maximum-permissible concentration – maximum concentration limit) makes only 0,01 mg/m3 of air when testing materials by chamber method. The plate materials released now can exceed DU of 17 times stated above. Despite attempts of institute Vniidrev through appeals to relevant authorities of the Ministry of Health to increase such admissible level in our country, generally for plate materials, were not crowned with success yet and this level in real time remains in force. It is possible to use such plates in premises only at very small saturation room void volume plates (the saturation is defined as the relation of surface area of plates indoors to room void volume). In foreign practice of DU of formaldehyde in air much higher and makes 0,124 mg/m3 of air. Results of researches of the maximum saturation (the relation of surface area of plates to room volume) depending on class of emission of DSTP and DU formaldehyde at values 0,01 and 0,124 of mg/m3 of air in relation to premises are given in the real work.

Fracture Areas Quantitative Investigating of Bending–Torsion Fatigued Low-Alloy High-Strength Steel

In this study, the impact of pseudo-random non-proportional bending-torsion fatigue loadings proportion on the fatigue life and the fracture surface topography was analyzed. Investigation was carried out for 24 specimens made of S355J2 steel with 11 different ratios of maximum stresses λ. For these cases, after the fatigue tests, the surface topography measurements were carried out using an optical profilometer, using the focus variation method. Three fracture zones were analyzed for each specimen: (1) total; (2) propagation; (3) rupture, taking into account the root average square height Sq and void volume Vv parameters. The results pointed that ratio of maximum stresses λ is the most influenced on volume surface parameters represented by void volume at a given height Vv, in the rupture area. A new fatigue loading parameter P was used, depending on fatigue life T and ratio of maximum stresses λ, which shows very good correlation in 4th degree type of fit, to void volume Vv parameter for the rupture area.

New insights into the role of porous microstructure on adiabatic shear localization

This paper provides new insights into the role of porous microstructure on adiabatic shear localization. For that purpose, we have performed 3D finite element calculations of electro-magnetically collapsing thick-walled cylinders. The geometry and dimensions of the cylindrical specimens are taken from the experiments of Lovinger et al. (2015), and the loading and boundary conditions from the 2D simulations performed by Lovinger et al. (2018). The mechanical behavior of the material is modeled as elastic-plastic, with yielding described by the von Mises criterion, an associated flow rule and isotropic hardening/softening, being the flow stress dependent on strain, strain rate and temperature. Moreover, plastic deformation is considered to be the only source of heat, and the analysis accounts for the thermal conductivity of the material. The distinctive feature of this work is that we have followed the methodology developed by Marvi-Mashhadi et al. (2021) to incorporate into the finite element calculations the actual porous microstructure of 4 different additively manufactured materials --aluminium alloy AlSi10Mg, stainless steel 316L, titanium alloy Ti6Al4V and Inconel 718-- for which the initial void volume fraction varies between 0.001% and 2%, and the pores size ranges from ≈ 6 µm to ≈ 110 µm. The numerical simulations have been performed using the Coupled Eulerian-Lagrangian approach available in ABAQUS/Explicit (2016) which allows to capture the shape evolution, coalescence and collapse of the voids at large strains. To the authors' knowledge, this paper contains the first finite element simulations with explicit representation of the material porosity which demonstrate that voids promote dynamic shear localization, acting as preferential sites for the nucleation of the shear bands, speeding up their development, and tailoring their direction of propagation. In addition, the numerical calculations bring out that for a given void volume fraction more shear bands are nucleated as the number of voids increases, while the shear bands are incepted earlier and develop faster as the size of the pores increases.

Influence of Thermochemical Treatment on the Surface Properties of Finish Turned Wire Arc Sprayed 17Cr Steel Coatings

Structural features of thermal spray coatings, e.g., porosity, can be beneficial as oil retention volumes in tribological systems in order to improve emergency running properties. While thermal spray coatings can already have a considerable degree of porosity depending on the coating conditions, the finish machining, e.g., by turning, has a significant influence on the final surface properties. Effects like near-surface deformation and subsequent closing of pores during the machining process should be prevented. In the present study, the influence of thermochemical surface hardening on the surface topography of wire arc sprayed 17Cr steel layers after finish turning was investigated. Successful surface hardening by gas nitriding was shown by light microscopic and phase analyses. The surface properties after the various treatment steps were characterized by the surface roughness parameters Ra and Rz, the valley void volume Vvv, and the Abbott curves. A rise of the valley void volume can be beneficial in tribological applications in which a suitable oil retention volume is required. Accordingly, a thermochemical treatment combined with an appropriate subsequent finishing process is suitable to significantly influence the surface properties of thermal spray steel coatings.

Experimental prediction of internal defects according to defect area on NDI via water absorption behavior

This study analyzed the relationship between the defect area identified through a C-scan and the void volume in CF-PEKK composite materials through the water absorption behavior to predict the void volume. The water absorption content varies with the defect area; however, the defect area identified through a C-scan and the water absorption content did not show a proportional relationship. This is because voids are distributed in the through-thickness. The results indicated that the absorption behavior could be used to predict the void volume. Irreversible absorption was found to be independent of the void volume. Further, no matrix degradation was seen with water immersion at [Formula: see text]C; however, some local swelling was seen.