Microtensile Testing Research Articles

Effectiveness of self-etching bonding systems on dentin after radiotherapy: perspectives on microtensile and microshear bond strength.

Self-etching dental adhesives bond with dentin through chemical reactions with calcium. This study assessed bond strength (BS) using microtensile (µTBS) and microshear (µSBS) tests on sound and post-radiotherapy dentin, with dental adhesives containing different functional monomers. Sound dentin (SD) and post-radiotherapy irradiated dentin (ID) were tested with two adhesive systems: Clearfil SE Bond (SE, 10-MDP-based) and FL Bond II (FL, containing carboxylic and phosphonic monomers with S-PRG bioactive particles). The tests occurred initially (24h) and six months later; fracture mode was also analyzed (40x). Ninety-six human molars were randomly assigned (n = 12), and half were irradiated with a 70Gy radiation dose. ForµTBS test, teeth were bonded,restored and sectioned them into beams (0.64 mm2). The µSBS test used filled transparent cylindrical matrices with resin composite and light-cured them after dental adhesive applications. Three-way ANOVA and Tukey's test (p < 0.05) analyzed the data. µTBS showed a significant substrate x adhesive interaction (p < 0.001), while µSBS was significant for all factors (p = 0.006). SE and FL performed better on SD and ID, respectively, in the µTBS test. As for µSBS, SE showed higher values on ID (p < 0.05). Lower BS values occurred for SD-FL and ID-SE after six months. Dental adhesive performance varied based on substrate type and test method. FL was more stable for ID in µTBS, while SE excelled in µSBS. As post-radiotherapy irradiated dentin becomes more vulnerable, self-etching systems based on functional monomer and bioactive ingredients may exhibit appropriate bonding to this altered substrate.

Optimal Geometry for Focused Ion Beam-Milled Samples for Direct-Pull Micro-Tensile Testing Performed In Situ in a Scanning Electron Microscope

A thorough procedure was developed to efficiently manufacture dogbone samples using focused ion beam (FIB) milling for micro-tensile testing. A Bruker PI 89 PicoIndenter, Billerica, MA, USA, was used as a case study, although the analysis and results are applicable to other micro-mechanical testing systems capable of mounting a standard, Ø12.7 mm × Ø3.2 mm pin, scanning electron microscopy (SEM) pin stub (Ted Pella, Redding, CA, USA). Nine dogbones were made from an Fe-45Cu alloy additively manufactured using powder-fed laser-directed energy deposition (DED-LB). Testing showed that fracture was confined to the gauge section for all dogbones and that the fracture mode, ductile vs. brittle, was entirely dependent on the grain orientation relative to the loading direction. The analysis showed that the measured plastic strain to failure can vary from &gt;11% (optimal geometry) to &lt;1% (non-optimal geometry) in micro-tensile testing of high-tensile-strength (&gt;1 GPa) metallic materials. Subsequently, a finite element analysis (FEA) was conducted to identify the improved dogbone geometries. A total of ten thousand dogbone geometries were tested, and their dimensions were defined by a set of four adjustable parameters (corner radius, load surface angle, load surface length, and dogbone head length). The gauge width and gauge length were fixed to 4 µm and 10 µm, respectively. Three-dimensional surface plots of the stress concentration as a function of two parameters were used to identify the optimal ranges of parameter values. The addition of maximum width and length constraints, measuring 25 µm and 30 µm, respectively, allowed us to identify an optimal geometry at load surface angles of 30° and 45°. Their respective dimensions (corner radius, load surface length, and dogbone head length) are, in µm, 12, 6, and 7 and 10, 7, and 7. Testing these two optimal geometries with a range of gauge lengths from 4 to 20 µm showed that smaller gauge lengths only slightly reduced the detrimental stress concentration outside the gauge section. However, smaller gauge lengths will notably improve the FIB surface polishing step as tapering is reduced with smaller dogbone lengths.

Post-localized blast experimental investigation of mechanical properties and microstructural evolutions in austenitic stainless steel 316L

Mechanical loading causes material deformation, resulting in changes in mechanical properties due to microstructural alterations such as the multiplication of dislocations and evolution of grain morphology. Blast loading, a condition where materials deform at high strain rates, results in significant plastic deformation. This rapid deformation induces intense mechanical stresses, causing complex microstructural changes that influence the mechanical behavior and performance of the materials. Consequently, designing structures to withstand blast loading requires understanding the relationship between microstructure and property evolution. As the primary objective of this study, post-localized blast experiments have been conducted to elucidate the variability in microstructural response of Austenitic stainless steel (ASS) 316 L, characterized by its face-centered cubic crystal structure. Localized blast loads were applied to square test plates, 2 mm thick, with a circular exposed area of 106 mm in diameter. Quantitative mechanical property data from key zones within the deformed dome were determined through using a novel micro-tensile testing approach and nanoindentation tests. Electron backscatter diffraction (EBSD) in scanning electron microscopy (SEM) technique was employed to characterize the microstructural changes in the selected samples. The results revealed that blast loading induced complex mechanical and microstructural changes in ASS 316 L, including enhanced material strength, reduced ductility, and significant alterations in grain orientation and misorientation distributions. The materials underwent significant strain hardening due to the increased stress and deformation, resulting in a more resistant to plastic deformation and the greatest internal strain accumulations. Texture analysis underscored the influence of deformation geometry, with Goss and Copper emerging as predominant texture components.

Predicting mechanical properties of low-alloy steels using features extracted from Electron Backscatter Diffraction characterization

Machine learning (ML) approaches have recently been increasingly employed to establish quantitative relationships between material composition, processing, microstructure, and properties. However, the complexities of microstructure pose challenges for straightforward modeling, thereby complicating research efforts. This study introduces a series of multi-parametric quantification methods based on Electron Backscatter Diffraction (EBSD) data tailored to the microstructural characteristics of low-alloy steels. These methods include quantification of boundary densities across various misorientation angles, distinct types of boundaries, and geometrically necessary dislocation densities. Through thermomechanical simulation and micro-tensile testing of low-alloy steels, data on yield and ultimate tensile strengths were obtained, alongside EBSD-based extraction of microstructure characteristics. Several ML methods, including Random Forest (RF), Gradient Boosting Decision Trees (GBDT), and Extreme Gradient Boosting (XGBoost), were utilized to predict yield strength (YS) and ultimate tensile strength (UTS) using the aforementioned microstructural features. The GBDT model outperformed other algorithms, demonstrating high accuracy in predicting YS, UTS, and elongation. The model achieved an Mean Squared Error (MSE) of 972.18, an Mean Absolute Error (MAE) of 24.75 and an Coefficient of Determination (R2) of 0.864 for YS, and an MSE of 812.28, an MAE of 22.87 and an R2 of 0.823 for UTS. These results confirm GBDT's effectiveness in predicting mechanical properties from microstructural data.This successful integration of ML with multi-parametric description microstructural features underscores its potential in facilitating material design and development processes.

Assessment of Surface Roughness, Color, and Bonding Efficacy: Self-Adhesive vs. Conventional Flowable Resin.

This in vitro study aimed to analyze the surface roughness (Ra) and color stability (ΔEab, ΔE00) following simulated mechanical brushing and to evaluate the microtensile (μTBS) of self-adhering resin flowable (SARF) to dentin. The selected materials were Constic, Yflow AS, and Tetric N flow (TNF/control). Thirty composite resin cylinders were fabricated for surface property evaluation. Ra and color were assessed both before and after simulated brushing. The thresholds of 50:50% perceptibility and acceptability of color differences in the evaluated resins were assessed. For μTBS analysis, fifteen molars were selected, sectioned to expose flat dentin surfaces, and restored according to the manufacturers' instructions for microtensile testing. There were statistically significant differences in Ra among the groups, with Constic exhibiting the highest Ra value (0.702 µm; p < 0.05), whereas Yflow AS presented the lowest Ra value (0.184 µm). No statistically significant difference in color was observed among the groups (p > 0.05). The 50:50% perceptibility and acceptability thresholds were set at 1.2 and 2.7 for ΔEab and 0.8 and 1.8 for ΔE 00. All the results fell within the acceptable limits. The mean μTBS values of Constic, Yflow AS, and TNF were 10.649 MPa, 8.170 MPa, and 33.669 MPa, respectively. This study revealed increased Ra and comparable color stability among all the tested composite resins after abrasion. However, the SARF exhibited lower μTBS compared to conventional using an adhesive system.

Effects of lactic acid etching on immediate and aged bond strength of resin-dentin bonding interface.

To investigate the effects of lactic acid etching on the immediate and aged bond strength of the resin-dentin bonding interface, the resin-dentin bonding interface was evaluated 24 hours and 6 months later. A total of 42 isolated third molars were randomly divided into 6 experimental groups according to different lactate concentration (35%, 40%, 45%) and acid etching time (30 s, 45 s), with 37% phosphoric acid etching 15 s as a control. In each group, dentin samples were etched under different acidic conditions and bonded with Adper Single Bond 2 (3M ESPE) as directed. The immediate group was immediately stored in deionized water at 37 °C for 24 h, and the aging group was stored in artificial saliva at 37 °C for 6 months. Immediate and aged bond strengths were measured by a micro-tensile tester, and the specimen fracture surface was observed under a microscope. 14 isolated third molars were randomly divided into 7 groups, and each group was etched with acid. Collagen fibers morphology in dentin was examined after gradient dehydration with ethanol by scanning electron microscopy (SEM). Statistically, there was no difference between the resin-dentin immediate bonding strength of 35% lactic acid for 30 s and 37% phosphoric acid for 15 s, but the aged bond strength was greater than that of the phosphoric acid group. According to scanning electron microscope observations, the collagen fiber morphology in 35% and 40% lactate etching dentin 30 s groups was relatively intact compared with other groups. In conclusion, 35% lactic acid etching of dentin 30 s ensures both immediate and aged resin-dentin bond strength.

The influence of neutral MDP-Na salt on dentin bond performance and remineralization potential of etch-&-rinse adhesive

ObjectivesTo investigate the effect of neutral 10-methacryloyloxydecyl dihydrogen phosphate salt (MDP-Na) on the dentin bond strength and remineralization potential of etch-&-rinse adhesive.MethodsTwo experimental etch-&-rinse adhesives were formulated by incorporating 0 wt% (E0) or 20 wt% (E20) neutral MDP-Na into a basic primer. A commercial adhesive, Adper Single Bond 2 (SB, 3 M ESPE), served as the control. Sixty prepared teeth were randomly allocated into three groups (n = 20) and bonded using either one of the experimental adhesives or SB. Following 24 h of water storage, the bonded specimens were sectioned into resin-dentin sticks, with four resin-dentin sticks obtained from each tooth for microtensile bond strength (MTBS) test. Half of the sticks from each group were immediately subjected to tensile loading using a microtensile tester at a crosshead speed of 1 mm/min, while the other half underwent tensile loading after 6-month incubation in artificial saliva (AS). The degree of conversion (DC) of both the control and experimental adhesives (n = 6 in each group) and the adsorption properties of MDP-Na on the dentin organic matrix (n = 5 in each group) were determined using Fourier-transform infrared spectrometry. Furthermore, the effectiveness of neutral MDP-Na in promoting the mineralization of two-dimensional collagen fibrils and the adhesive-dentin interface was explored using transmission electron microscopy and selected-area electron diffraction. Two- and one-way ANOVA was employed to assess the impact of adhesive type and water storage on dentin bond strength and the DC (α = 0.05).ResultsThe addition of MDP-Na into the primer increased both the short- and long-term MTBS of the experimental adhesives (p = 0.00). No difference was noted in the DC between the control, E0 and E20 groups (p = 0.366). The MDP-Na remained absorbed on the demineralized dentin even after thorough rinsing. The intra- and extra-fibrillar mineralization of the two-dimensional collagen fibril and dentin bond hybrid layer was confirmed by transmission electron microscopy and selected-area electron diffraction when the primer was added with MDP-Na.ConclusionsThe use of neutral MDP-Na results in high-quality hybrid layer that increase the dentin bond strength of etch-&-rinse adhesive and provides the adhesive with remineralizing capability. This approach may represent a suitable bonding strategy for improving the dentin bond strength and durability of etch-&-rinse adhesive.

Effect of phosphoric acid etching and blasting with aluminum oxide on the enamel topography and adhesion of resin composite to intact or abraded enamel

ObjectivesTo evaluate the effects of the phosphoric acid (PA) etching, self-etching technique (SE) and blasting with Al2O3 particles (BL) on the bonding of a dental adhesive to intact (INT) or abraded (ABR) enamel. MethodsEnamel surfaces were treated as follows: 1- ABR-PA: INT was abraded with SiC paper and etched with PA (20 s) before Clearfil Universal Bond Quick adhesive application; 2- ABR-SE: ABR was SiC and adhesive applied in SE mode; 3- INT-PA: INT was etched with PA and adhesive applied; 4- INT-SE: the adhesive (SE mode) was applied to INT; 5- INT-BL: INT was BL and the adhesive was applied (SE mode), and 6- INT-BA: INT was BL, etched with PA and adhesive applied (SE mode). The enamel surface treated was examined with scanning electron microscopy (SEM) (n = 3) and Al2O3 particles were characterized using SEM and EDX. The enamel bond strength was measured by microtensile test (24 h and 1 year) (n = 8) and the morphology of enamel-adhesive interfaces were analyzed by SEM (n = 3). Bond strength data were analyzed by two-way ANOVA and Tukey’s test (α = 0.05). ResultsAl2O3 particles had an irregular shape, their length varied (50–20 µm) and the perimeter mean was 38.8 µm. The enamel morphology significantly influenced the enamel bond strength. ABR-PA, INT-BL, and INT-BA provided greater and stable enamel-dentin interaction and bond strength. SignificanceThe enamel morphology significantly influenced the enamel bond strength. Using the adhesive in etch-and-rinse mode, enamel must be abraded before etching and must be Al2O3-blasted when used in SE mode.

The Effect Of Different Caries Removal Methods On The Surface Hardness and Micro-tensile Bond Strength

Objective: This study aims to evaluate the effects of five different caries removal methods on caries removal effectiveness according to microhardness and micro tensile bond strength values. Materials: In this study, for the microhardness test, micro-tensile bond strength test (n = 10) SEM analysis (n = 2), and a total of 72 human molar teeth were used. Caries lesions were removed with conventional (steel bur, ceramic bur, polymer bur) methods, chemomechanical method (Brix-3000), and fluorescence-aided caries excavation method (Siroinspect). Then, teeth were sectioned longitudinally through the cavity center and were subjected to the microhardness test, micro tensile test, and SEM atomic analysis. Statistical analyses were performed using one-way ANOVA and Duncan post-hoc tests. Results: A statistically significant difference was found between all caries removal methods and measurement levels at certain distances from the cavity floor (0, 25, 50, 75 μm) (p

Influence of bioceramic sealer residues on the adhesion interface with a universal adhesive in the etch-and-rinse strategy, based on the application protocol and evaluation time.

The aim of this study was to evaluate the effects of the application of universal adhesive in the etch-and-rinse (ER) strategy with a manual brush (MB) or rotary brush (RB) in adhesion to dentin impregnated (WB) or not (NB) with bioceramic sealer, at 24 h and 1 year. Eighty-eight crowns of bovine incisors were divided into four groups (n=22): WB-MB, WB-RB, NB-MB, NB-RB. After the restorative protocol, dentin penetrability was evaluated by confocal microscopy. Bond strength was evaluated by microtensile test. Data were analyzed using one-way ANOVA/Tukey tests (α=0.05). NB-RB and WB-RB exhibited greater extensions of resin tags in dentin. At 24 h, WB-RB and NB-MB showed the highest and lowest values of bond strength, respectively. At 1 year, WB-MB and WB-RB demonstrated the highest bond strength values. The RB increases the formation of resin tags and residues of bioceramic sealer provides higher bond strength in the ER strategy.

Effects of the application protocol and bonding strategy of the universal adhesive on dentin previously impregnated with bioceramic sealer

PurposeTo evaluate the effects of the application of universal adhesive with manual brush (MB) or rotary brush (RB), in the etch-and-rinse (ER) or self-etching (SE) strategy, on the bond strength, adhesive layer thickness, and adhesive failure pattern to dentin impregnated with bioceramic sealer, at 24 h and 1 year. Materials and methodsEighty-eight bovine incisor crowns were impregnated with bioceramic sealer was kept for 15 min and cleaned with cotton soaked in distilled water. They were then divided into four groups (n = 22): ER-MB, ER-RB, SE-MB, SE-RB. Subsequently, the specimens were restored with Filtek Z-250 resin. The adhesive layer thickness was individually analyzed using laser confocal microscope. Bond strength was assessed through microtensile testing, and the failure pattern was examined using a stereomicroscope. Data were analyzed by one-way ANOVA/Tukey's tests (α = 0.05). ResultsThe adhesive layer thickness provided by ER-MB and SE-MB was greater than that provided by ER-RB and SE-RB (P < 0.05). ER-MB showed the lowest bond strength at 24 h (P < 0.05). At 1 year, SE-MB and SE-RB exhibited the highest bond strength values (P < 0.05). ER-MB demonstrated a higher incidence of adhesive failure at 24 h. At 1 year, SE-RB and SE-MB showed a higher incidence of mixed failure. ConclusionThe use of Scotchbond Universal® adhesive in the etch-and-rinse strategy applied with a MB negatively affects bond strength at 24 h, worsening after 1 year of control, regardless of the application protocol.

Comparison analysis of moisture-dependent orthotropic elasticity between earlywood and latewood in Chinese fir using digital image correlation

Given its orthotropic and hygroscopic nature, Chinese fir exhibits varying mechanical behaviors in earlywood and latewood due to its naturally inhomogeneous structure when exposed to changes in loading direction and given moisture content (MC) range from 7.9 % to 16.1 %. In this study, we combined micro-tensile testing and the digital image correlation (DIC) technique to derive the moisture -dependent orthotropic elastic constants, i.e., Young’s modulus (E), Poisson’s ratio (ν) and shear modulus (G) for both earlywood and latewood in Chinese fir. The findings revealed that when loading in the parallel direction, the restraining effect caused by latewood on earlywood resulted in a difference compared with loading in series. Interestingly, the loading direction impacted the restraining effect more significantly than MC. Additionally, both Young’s modulus and shear modulus exhibited decreases with increasing MC within above range for both earlywood and latewood. Notably, the Young’s modulus of earlywood showed a higher sensitivity to MC variations compared to latewood. However, Poisson’s ratio did not consistently correlate with MC within above range in all orthotropic directions. A three-dimensional coordinate system visualization of the compliance parameters highlighted the differing sensitivities of earlywood and latewood to moisture. The independent moisture-dependent elastic components of earlywood and latewood derived in this study extended the moisture-dependent mechanical model of wood, offering theoretical guidance for the practical application of Chinese fir and other wood species.

Effect of radiotherapy, immediate dentin sealing and irrigation simulating single- or two-visits endodontic treatment on the bond strength to pulp chamber dentin: an in vitro study.

This study aimed to evaluate the influence of radiotherapy and different endodontic treatment protocols on the bond strength to pulp chamber dentin. Eighty mandibular molars were randomly divided into two groups (n = 40): non-irradiated and irradiated (60Gy). The pulp chambers were sectioned, and each group was subdivided (n = 8), according to the endodontic treatment protocol: no treatment (Control); Single-visit; Two-visits; Immediate dentin sealing (IDS) + single-visit; and IDS + two-visits. Each endodontic treatment visit was simulated through irrigation with 2.5% NaOCl, 17% EDTA and distilled water. IDS was performed by actively applying two coats of a universal adhesive to the lateral walls of the pulp chamber. After, the pulp chambers were restored with resin composite and four sticks were obtained for microtensile test. In addition, the dentin of the pulp chamber roof was assessed for surface roughness, chemical composition, and topography after each treatment protocol. Two-way ANOVA, Tukey's post hoc, Mann-Whitney, Kruskal-Wallis and Dunn's post hoc were performed (α = 5%). The treatment protocol affected bond strength (p < 0.05), while the irradiation did not (p > 0.05). The control group presented the highest values (p < 0.05). The single-visit group demonstrated better performance compared to the other groups (p < 0.05), which did not differ from each other (p > 0.05) The use of IDS changed the surface roughness (p < 0.05), chemical composition (p < 0.05) and topography of the dentin. In conclusion, the treatment protocol influenced dentin adhesion, while irradiation did not.

Correlating microstructure and mechanical properties of harvested high dose Zorita light water reactor internals

In this study, microstructural studies and micro-mechanical testing of an ex-plant material harvested from the decommissioned pressurized water reactor (PWR) is carried out. Irradiated 304 stainless steel (SS) components were harvested by the Electric Power Research Institute, U.S. Nuclear Regulatory Commission, and members of the José Cabrera Nuclear Power Station (Zorita) in Spain. The bi-crystalline micro-tensile specimens, atom probe tomography (APT) tips, and transmission electron microscopy (TEM) lamellae were fabricated from the baffle plate materials irradiated to 0.05, 15 and 50 dpa to elucidate microstructural, microchemical, and local mechanical properties changes as a function of dose. TEM and APT studies reveal radiation induced Ni, Cr, and Si rich precipitates in the 15 dpa sample that become smaller and partially redissolve into the matrix of the 50 dpa sample (decreasing size and number density). Dislocation loop and cavity number density and size were quantified as a function of dose as well as swelling. Intergranular Ni and Si enrichments with concomitant Fe and Cr depletion were observed in the 15 dpa sample and were more pronounced in the 50 dpa sample. Micro-tensile testing performed in the scanning electron microscope (SEM) at room temperature and 300 °C shows that the material's local yield strength and ultimate tensile strength decreases with increased dose and elevated test temperature and provides further insights via localized strain mapping. Current and previous mechanical data was compared with calculated values using the dispersed barrier hardening model with inputs of dislocation loops, precipitates, and cavities from microstructural characterization.

Microstructural and micromechanical characterization of Cr diffusion barrier in ATR irradiated U-10Zr metallic fuel

Chromium (Cr) has been recognized as a promising diffusion barrier candidate to mitigate the Fuel Cladding Chemical Interaction (FCCI) failure in metallic fuels for sodium-cooled fast reactor. This paper, for the first time, conducted an in-depth post-irradiation examination of the microstructure and composition evolution, and micromechanics of the Cr diffusion barrier in U-10Zr fuel/HT9 cladding irradiated in the Advanced Test Reactor (ATR) to 8.7% burnup at an averaged Peak Inner Cladding Temperature of 540–550 °C. Transmission Electron Microscope (TEM) characterization confirmed the preferential intergranular diffusion of Zr and U in the Cr diffusion barrier, suggesting that grain boundaries served as fast path for the diffusion of Zr and U into the Cr diffusion barrier. The interaction zone is dominated by nano crystalline α-ZrCr2 Laves phase. Despite the interaction, there is no microcracks being observed in the preserved Cr diffusion barrier and HT9 cladding, serving as a good barrier to mitigate FCCI under the studied in-reactor irradiation conditions. High density cavities in uniform distribution are observed inside Cr grains, nano particles contains Cr, Mn, and O are confirmed by Electron Energy Loss Spectroscopy (EELS) analysis. However, it is unclear whether the cavities will become an issue to the barrier integrity at higher burnup. In-situ Scanning Electron Microscopy (SEM) micro-tensile testing uncovered mechanical softening in the HT9 cladding nearing the Cr diffusion barrier, possibly due to the coarsening of lath structure and carbides precipitates.

Development of High-Sensitivity Thermoplastic Polyurethane/Single-Walled Carbon Nanotube Strain Sensors through Solution Electrospinning Process Technique

In this study, nanofibers obtained through the electrospinning process are explored for strain-sensing applications. Thermoplastic polyurethane (TPU) flexible structures were fabricated using the solution electrospinning process (SEP) technique. Subsequently, these structures were nanomodified with single-walled carbon nanotubes (SWCNTs) through immersion into an ultrasonicated suspension containing 0.3 wt% SWCNTs. The nanomodification aimed to impart an electrically conductive network to the structures. Micro-tensile tests and electrical resistance measurements were conducted to characterize the apparent mechanical and electrical properties, respectively. The fabricated structures demonstrated potential as wearable strain sensors for monitoring changes in strain across various applications. The samples exhibited excellent performance, high sensitivity, outstanding mechanical properties, and a broad stretching range. Scanning electron microscopy (SEM) observations provided qualitative insights into the activated conductive pathways during operation.

Modeling the heterogeneous and anisotropic plastic deformation of lath martensite

The plastic behavior of microscale lath martensite samples is highly anisotropic. Depending on the orientation, the deformation of such samples may be heterogeneous, with only a few localized slip traces, while the remainder of the sample remains largely elastic. Although several continuum plasticity models that account for the anisotropy exist, they cannot reproduce the heterogeneous response observed in experiments. In this study, a model for lath martensite at the microscale is proposed which captures the orientation-dependent heterogeneous behavior observed in experiments. Before formulating the model we first study in detail two idealized cases, in which two different deformation mechanisms are activated. In both cases, the lath martensite is modeled using a discrete slip plane model. In the model, the activation stress of the individual slip systems varies randomly in space according to a distribution based on the underlying dislocation motion. The two configurations differ only in the orientation of the applied tensile load relative to that of the laths — either perpendicular or at 45°. In the latter case, slip along the so-called habit plane results in localized plastic deformation, while the former results in a more diffuse activation of plasticity. Insights obtained based on the idealized cases are used to formulate a three-dimensional constitutive model which captures both deformation mechanisms. The model is applied to microtensile tests of single-packet lath martensite samples. It is shown that the orientation-dependent heterogeneity is accurately captured by the two deformation mechanisms accounted for by the model.

Bond Strength of Resin Cement Following Biomimetic Remineralization: An in vitro Study

Objectives This research assessed the efficacy of self-assembling peptide P11-4 (Curodont protect) in promoting biomimetic remineralization of dentin, thereby stabilizing the hybrid layer and enhancing the long-lasting of the resin-dentin bond. Methods Five premolar teeth were longitudinally sectioned to assess dentin microhardness before and after demineralization, as well as after the application of P11-4 (Curodont protect). For the microtensile test, ten premolar teeth were sectioned perpendicular to their long axes. The teeth were assigned to different groups. Following acid etching and rinsing, samples in control group I received no pretreatment, while the prepared dentin surface of group II was treated with 0.1 mL of P11-4 before the placement of the adhesive restoration. All specimens were stored in distilled water at 37 ± 2 °C for 24 hours and then underwent thermocycling. The microtensile test was measured, and the type of bond failure was evaluated. The obtained information, expressed in megapascals, was analyzed using a one-way analysis of variance (ANOVA), followed by Tukey’s multiple post hoc test. Results There was a statistically significant difference in hardness values after demineralization, followed by a significant increase in hardness after the application of P11-4 (Curodont protect) (p &lt; 0.001, effect size = 0.985). No statistically significant difference was found in the microtensile bond strength between the two groups (p = 0.384, effect size = 0.582). Adhesive-type failure was more commonly observed. Conclusion The use of self-assembling peptide P11-4 (Curodont protect) on dentin resulted in higher microhardness than the control group without adversely affecting resin cement bond strength.

Microstructure evolution in AM produced superalloy thin struts at low plastic strain

This paper discusses the microstructures and textures that develop in thin struts fabricated in Inconel 718 using laser melting powder bed fusion. Thin struts 1 mm wide were fabricated in the vertical (ZX) and horizontal build (XY) orientations with respect to the build plate. Three distinct regions of well-defined grain structures with centerline symmetry from the outer border to the center of the inner volume were present, which was attributed to the laser scan strategy, consisting of a fill hatch, inner and outer border scan on each 30 μm layer. Using ex situ micro-tensile testing and enhanced Back-Scattered Electrons (BSE) and Electron Back Scattered Diffraction (EBSD), the microstructure evolution to a plastic strain near 1%, in both the ZX and XY build direction was studied in the initial undeformed and final deformed states. For the ZX build direction, grain rotation as well as grain boundary migration was observed and was more significant than in the samples fabricated in XY. This paper discusses the evolution of the microstructure offering valuable insights into the relationship between microstructure and mechanical properties in complex AM produced microstructures.

EVALUATION OF BOND STRENGTH OF NEWER BONDING AGENTS TO HUMAN DENTIN AFTER SIX MONTHS OF STORAGE AN ANALYTIC STUDY

Introduction: Among various materials, composite resins have been developed in order to provide the best aesthetics to the anterior restorations as well as for posterior restorations. Resin-dentin bonds are more difficult to achieve than resin-enamel bonds, because dentin bonding relies on organic components. Materials &amp; Methodology: A total number of 44 extracted human mandibular premolars were collected. Occlusal enamel surface was removed using an airotor and diamond bur.The collected 44 teeth were divided in to four groups according to the bonding agents used. 1st sub group with five teeth that is submitted for microtensile testing within 24 hours and SEM analysis for failure mode, 2nd sub-group contains five teeth which is submitted to microtensile bond strength after six months of storage in normal saline and thereafter for SEM analysis for failure mode, and the 3rd sub-group with one teeth which is prepared for analyzing the bond interface using SEM Results: Summarized data was presented using Tables. Data was normally distributed as tested using the Shaperio‑Wilk W test (p-value was less than 0.05). Therefore, analysis was performed using the parametric tests i.e. Independentt test (for comparing two groups) and One way Anova test (for comparing more than two groups). Level of statistical significance was set at p-value less than 0.05. Conclusion:The lowest bond strength values both at 24 hours and after 6 months in normal saline due to its solvent system (acetone, ethanol, water), which might not create a stable adhesive layer like other agents. Optimal filler load could also reduce bond strength by limiting resin availability. SEM analysis revealed that fewer resin tags, indicating incomplete penetration into dentinal tubules, resulting in weaker bonding and susceptibility to degradation. Adhesive failures indicating poor adhesion at the dentin interface, while mixed failures suggested inadequate bonding with the composite resin. This underscores the importance of refining bonding agent formulations and application techniques to ensure enduring adhesive bonds in restorative dentistry.