Average Fracture Research Articles

Management of paediatric fifth metacarpal neck fractures: a systematic review.

Fifth metacarpal neck fractures (FMCNFs) are common among paediatric patients. Complications include reduced metacarpophalangeal (MCP) range of motion and grip strength, which impede the hand's functional abilities. Various management options are available, but indications are not standardised. This systematic review aims to assimilate all available evidence on the management of paediatric FMCNFs to determine appropriate treatment pathways. PubMed (Medline), EMBASE, Scopus and Google Scholar were used to identify evidence pertaining to the management of these fractures. Ten studies were identified, involving 237 patients with a mean age of 14.4years (Range 9-17). Ninety percent of patients were male. Sixty-one (26%) patients, with an average fracture angulation of 27° (Range 16°-33°) and no rotational deformities, were managed with immobilisation alone. These patients returned to normal metacarpophalangeal range of motion and grip strength. Fifty-four (23%) patients, with an average fracture angulation of 42.7° (Range 33°-54°), were managed with fracture reduction and immobilisation. This technique did not yield sustained reduction of fractures with significant angulation or rotation after intervention. One hundred twenty-two (51%) patients, with an average fracture angulation of 48.3° (Range 30°-58°) and including cases of malrotation, were managed with fracture reduction and surgical fixation. These patients experienced good functional outcomes. This review suggests paediatric FMCNFs can be safely managed with immobilisation alone when there is an absence of rotational deformity and an angulation of < 30°. In the case of a higher fracture angulation or rotational deformity, fracture reduction and surgical fixation is an appropriate method of management.

Temporal Variations in Frequency‐Dependent Shear‐Wave Anisotropy Above a Plate Interface Following Episodic Slow‐Slip Events

AbstractRecent observations beneath Kanto, Japan have shown that seismic activity and seismic attenuation within the overlying continental plate change with time due to drainage caused by slow‐slip events (SSEs) along the upper boundary of the Philippine Sea plate. However, associated changes in rock properties have not been investigated. In this study, we estimate frequency‐dependent shear‐wave anisotropy to provide a detailed insight into the structural change associated with drainage. We perform shear‐wave splitting analysis in frequency ranges of 1–4, 2–6, and 4–8 Hz for 306 earthquakes that occur during September 2009–August 2021 and recorded at the Metropolitan Seismic Observation network. Obtained time differences between fast and slow S waves (delay time) range from almost zero to 0.16–0.18 s, exhibiting spatio‐temporal variation and frequency dependence. The fast S‐wave polarization directions are generally consistent with the direction of the maximum horizontal compressional axis in the study region, which suggests that the observed anisotropy is probably caused by the NE–SW‐oriented fractures developed under the regional stress field. The temporal variation in delay times is correlated with SSEs activity with a lag time of 0.0–0.1 year. Furthermore, comparisons between observed frequency‐dependent delay times and numerical calculation of fracture‐induced anisotropy suggest that the average fracture radius is almost constant (0.30–0.35 m) over time but fracture density temporally varies from 0.025 to 0.035. We infer that the fracture density is probably enhanced by opening of the NE–SW‐oriented fractures during the upward migration of fluids that are expelled from the plate interface.

Fracture resistance of cement-retained lithium disilicate implant-supported crowns: Effect of material used for two-piece abutments.

This study compared the fracture strength of single lithium disilicate implant-supported crowns fabricated on two-piece abutments with various materials: ceramic-reinforced PEEK, zirconia, and lithium disilicate. Thirty-six implants were embedded in acrylic cylinders. A two-piece abutment and a crown were designed following a pre-operation scan for a maxillary left central incisor. The designed crown was used to fabricate 36 lithium disilicate crowns. The designed abutment was used to manufacture 36 abutments from 3 materials, 12 each: (A) zirconia; (B) lithium disilicate; and (C) ceramic-reinforced PEEK. Abutments were surface treated and bonded on the titanium base abutments with resin cement. Then, lithium disilicate crowns were bonded on the assigned abutments. Specimens were then subjected to dynamic loading for 1,200,000 cycles. The fracture strength (N) of the assembly was assessed using a universal testing machine. One-way ANOVA followed by multiple comparison tests was used to evaluate the effect of abutment material on the fracture strength of single implant-supported restorations at a significance of .05. The average fracture strength for the groups with zirconia, PEEK, and lithium disilicate two-piece abutments were 1362N ± 218N, 1235N ± 115N, and 1472N ± 171N, respectively. There was a significant (p < 0.05) difference in fracture strength among the groups. The lithium disilicate group had significantly higher fracture strength (p = 0.0058) than the group with PEEK; however, there was no significant (p > 0.05) difference between the other groups. Two-piece abutments restored with lithium disilicate crowns investigated in the study have the potential to withstand the average physiological occlusal forces in the anterior region.

Effects of polyvinylpyrrolidone on the crystallization of amorphous griseofulvin: fracture and molecular mobility

This study aims to investigate the fracture, molecular mobility and crystallization behaviors of amorphous griseofulvin (GSF) in the presence of polyvinylpyrrolidone (PVP). In the presence of 10%(w/w) PVP K90, the fracture resistance of griseofulvin was greatly improved. Compared with the pure GSF system, the average fracture temperature of the griseofulvin–PVP K90 system was decreased to approximately −6.1°C. More importantly, a statistical study revealed that the direct connection between fracture and nucleation of griseofulvin was weakened in the presence of PVP K90. This study also explored the effects of PVP K90 on the molecular dynamics and crystallization behaviors of amorphous GSF. In the presence of PVP K90, the crystal growth kinetics and molecular dynamics were both slowed down. Interestingly, needle-like crystal growth was observed, exhibiting approximately the same rates as the bubble-induced process. These findings are important for understanding the complex mechanisms of physical stability of polymer-based amorphous solid dispersions.

The Impact of Bonding Agents and Bone Defects on the Fracture Resistance of Reattached Vertically Root-Fractured Teeth

Many patients experience vertical root fractures, and clinicians often consider conservative treatment options like reattaching the fractured root segments. The study investigated the impact of different bonding agents on the fracture resistance of rebonded vertically fractured teeth with various alveolar bone defects. Human premolar teeth with a single root were sectioned and reattached using dual-cure resin cement (DCRC), resin-modified glass ionomer (RMGI), and cyanoacrylate. The reattached teeth were then restored with a resin fiber post, composite resin core, and full veneer metal copings. These teeth were embedded in acrylic blocks with angular, V-shaped, and step-shaped bone defects to simulate various alveolar bone conditions. After subjecting the samples to thermal cycling, the fracture resistance was evaluated using a universal testing machine. Teeth samples reattached with RMGI exhibited a higher average fracture resistance. The study also found that DCRC proved to be an effective bonding agent for VRF teeth. However, cyanoacrylate-rebonded teeth exhibited the lowest fracture resistance. The V-shaped defects had a significant impact on the fracture resistance of reattached VRF teeth, with largely unfavorable fractures observed in these cases. Predominantly favorable fractures were observed in the teeth treated with RMGI. The fracture loads in both RMGI and DCRC groups exceeded the expected masticatory load.

Biomechanical analysis of a new cannulated screw for unstable femoral neck fractures.

The treatment of unstable femoral neck fractures (FNFs) remains a challenge. In this study, a new cannulated screw for unstable FNFs was designed to provide a new approach for the clinical treatment of these injuries, and its biomechanical stability was analyzed using finite element analysis and mechanical tests. An unstable FNF model was established. An internal fixation model with parallel inverted triangular cannulated screws (CSs) and a configuration with two superior cannulated screws and one inferior new cannulated screw (NCS) were used. The biomechanical properties of the two fixation methods were compared and analyzed by using finite element analysis and mechanical tests. The NCS model outperformed the CSs model in terms of strain and stress distribution in computer-simulated reconstruction of the inverted triangular cannulated screw fixation model for unstable FNFs. In the biomechanical test, the NCS group showed significantly smaller average femoral deformation (1.08 ± 0.15mm vs. 1.50 ± 0.37mm) and fracture line displacement (1.43 ± 0.30mm vs. 2.01 ± 0.47mm). In the NCS group, the mean stiffness was significantly higher than that in the CSs group (729.37 ± 82.20N/mm vs. 544.83 ± 116.07N/mm), and the mean compression distance was significantly lower than that in the CSs group (2.87 ± 0.30mm vs. 4.04 ± 1.09mm). The NCS combined with two ordinary cannulated screws in an inverted triangle structure to fix unstable FNFs can provide better biomechanical stability than CSs and exhibit a length- and angle-stable construct to prevent significant femoral neck shortening.

Analysis of fracture mechanism and fracture energy prediction of lightweight aggregate concrete

The fracture energy of lightweight aggregate concrete (LWAC) is comparatively lower than that of normal weight concrete (NWC), primarily due to the propensity for fracture exhibited by lightweight aggregates and their characteristics that modify the damage softening mechanism at the crack tip. Few studies have been done on how to precisely predict the LWAC fracture energy. In this work, 111 sets of three-point bending test data were gathered, and the impact of aggregate types and size, concrete density, water-cement (w/c) ratio, and compressive strength on the total average fracture energy (GF) and the initial fracture energy (Gf) was thoroughly evaluated. Five fracture energy prediction methods’ applicability were compared, and a fracture energy prediction expression appropriate for LWAC was presented. Finally, the three-point bending test was used to confirm the prediction. The results show that the fracture energy of LWAC is significantly influenced by changes in aggregate and mortar characteristics. The compressive strength has substantial correlations with the fracture energy of LWAC. After adjusting the aggregate and mortar coefficients, the prediction formula can correctly predict Gf and GF.

Fracture resistance and failure mode of three esthetic CAD-CAM post and core restorations

BackgroundThe rising demand for improved aesthetics has driven the utilization of recently introduced aesthetic materials for creating custom post and core restorations. However, information regarding the fracture resistance of these materials remains unclear, which limits their practical use as custom post and core restorations in clinical applications.Aim of the studyThis study aimed to evaluate the fracture resistance of three non-metallic esthetic post and core restorations and their modes of failure.Materials and methodsThirty-nine single-rooted human maxillary central incisors were endodontically treated. A standardized post space preparation of 9mm length was performed to all teeth to receive custom-made post and core restorations. The prepared teeth were randomly allocated to receive a post and core restoration made of one of the following materials (n=13): glass fiber-reinforced composite (FRC), polyetheretherketone (PEEK) and polymer-infiltrated ceramic-network (PICN). An intraoral scanner was used to scan all teeth including the post spaces. Computer-aided design and computer-aided manufacturing (CAD-CAM) was used to fabricate post and core restorations. Post and core restorations were cemented using self-adhesive resin cement. All specimens were subjected to fracture resistance testing using a universal testing machine. Failure mode analysis was assessed using a stereomicroscope and SEM. The data was statistically analyzed using One-Way ANOVA test followed by multiple pairwise comparisons using Bonferroni adjusted significance level.ResultsCustom PEEK post and core restorations displayed the least fracture load values at 286.16 ± 67.09 N. In contrast, FRC exhibited the highest average fracture load at 452.60 ± 105.90 N, closely followed by PICN at 426.76 ± 77.99 N. In terms of failure modes, 46.2% of specimens with PICN were deemed non-restorable, while for PEEK and FRC, these percentages were 58.8% and 61.5%, respectively.ConclusionsWithin the limitation of this study, both FRC and PICN demonstrated good performance regarding fracture resistance, surpassing that of PEEK.

The effect of Ding’s screws and tension band wiring for treatment of olecranon fractures: a biomechanical study

Although tension band wiring (TBW) is popular and recommended by the AO group, the high rate of complications such as skin irritation and migration of the K-wires cannot be ignored. Ding’s screw tension band wiring (DSTBW) is a new TBW technique that has shown positive results in the treatment of other fracture types. The objective of this study was to evaluate the stability of DSTBW in the treatment of olecranon fractures by biomechanical testing. We conducted a Synbone biomechanical model by using three fixation methods: DSTBW, intramedullary screw and tension band wiring (IM-TBW), and K-wire TBW, were simulated to fix the olecranon fractures. We compared the mechanical stability of DSTBW, IM-TBW, and TBW in the Mayo Type IIA olecranon fracture Synbone model using a single cycle loading to failure protocol or pullout force. During biomechanical testing, the average fracture gap measurements were recorded at varying flexion angles in three different groups: TBW, IM-TBW, and DSTBW. The TBW group exhibited measurements of 0.982 mm, 0.380 mm, 0.613 mm, and 1.285 mm at flexion angles of 0°, 30°, 60°, and 90° respectively. The IM-TBW group displayed average fracture gap measurements of 0.953 mm, 0.366 mm, 0.588 mm, and 1.240 mm at each of the corresponding flexion angles. The DSTBW group showed average fracture gap measurements of 0.933 mm, 0.358 mm, 0.543 mm, and 1.106 mm at the same flexion angles. No specimen failed in each group during the cyclic loading phase. Compared with the IM-TBW and TBW groups, the DSTBW group showed significant differences in 60° and 90° flexion angles. The mean maximum failure load was 1229.1 ± 110.0 N in the DSTBW group, 990.3 ± 40.7 N in the IM-TBW group, and 833.1 ± 68.7 N in the TBW group. There was significant difference between each groups (p < 0.001).The average maximum pullout strength for TBW was measured at 57.6 ± 5.1 N, 480.3 ± 39.5 N for IM-TBW, and 1324.0 ± 43.8 N for DSTBW. The difference between maximum pullout strength of both methods was significant to p < 0.0001. DSTBW fixation provides more stability than IM-TBW and TBW fixation models for olecranon fractures.

Influence of laser treatment on the microstructural evolution and performance of Ti65 alloy

Achieving simultaneous increase in strength and plasticity of metallic materials is a long-term challenge. In this study, we prepared the Ti65 alloy with surface refined structure by laser treatment and studied the evolution of surface and cross-sectional microstructure, as well as its impact on tensile properties. The tensile strength of the Ti65 alloy sheet increases from 1098 to 1136 MPa after laser treatment, and the average fracture strain significantly rises from 6.81% to 10.23%, marking a substantial 50.2% increment. During laser treatment, the fast cooling rate caused the formation of a strengthening layer with fine grains, which leads to an increase in strain hardening rate and non-uniform deformation induced strengthening provided by non-uniform structures. The findings in this work provide a new routine for upgrading mechanical properties of titanium alloy through generating a strengthening layer with fine grains on the surface.

Analytic representative element rate decline models for naturally fractured reservoir depletion

Representative single anisotropic matrix block 2D Green’s function models for depletion through fully-penetrating, vertical fractures through different numbers of fracture faces are constructed that analytically capture both fracture and block depletion with fracture-matrix mass transfer. The 1D Green’s function for a fracture system is likewise solved in terms of the time evolution of average fracture pressure. While transient average pressure values are not inherently measurable, they are transformed into cumulative production or instantaneous flowrate values, thus producing new rate decline model functional forms. Primary variables in assembling the interacting systems model are the volume ratio, Vf /Vm, permeability ratio, kf /kx, and geometry, (a/b)(ky/kx), with the last term accounting for both block shape and permeability anisotropy. We construct interacting systems models in terms of various ratios of Vf /Vm, and kf /kx for three fracture architecture prototypes: representative matrix blocks depleted by 4, 2, or 1 contacting fractures. The single matrix block models can be migrated to ones for heterogeneous systems using superposition and matrix block distributions, as demonstrated with a binary distribution of block sizes with variable fractions. Analytic solutions for rate decline problems can be used to understand the production signatures of naturally fractured reservoirs and interpretation of fracture volume fraction, permeability ratio, average matrix block size, and measures of heterogeneity.

Effect of Cold Isostatic Pressing and VC Grain Growth Inhibitor Addition on WC Grain Size and Mechanical Properties of WC-8Co Cemented Carbide

In this study, sub-micron WC-Co cemented carbides were fabricated by cold isostatic pressing using recycled WC powder, Co powder, and VC grain growth inhibitor as the initial composite powders. The raw WC-8Co and WC-8Co-0.3VC compositions were prepared according to conventional technology. After that, part of the green compacts was CIP-ed under pressure of 200 MPa. Sintering was carried out in an industrial vacuum sintering furnace at a temperature of 1420 ºC simultaneously for all samples. The microstructures and properties, including density, coercivity, transverse rupture strength, A-type Rockwell hardness and fracture toughness were investigated, characterized and compared systematically. The experimental results showed that the action of cold isostatic pressing in combination with grain growth inhibitor addition promoted ultrafine grains with the finest WC grain size of 0.68 μm and an increase in the fracture toughness up to 15.4 MPa·m1/2 ± 0.2 compared to rest cemented carbides, showing the techniquehas potential to fabricate cermets with both small average WC grain size and high fracture toughness, which is key in providing excellent performance.

A Combined Experimental and Numerical Calibration Approach for Modeling the Performance of Aerospace-Grade Titanium Alloy Products

Finite element modeling for designing and optimizing lightweight titanium aerospace components requires advanced simulation tools with adequate material modeling. In this sense, a hybrid strategy is proposed in this work to identify the parameters of the Johnson–Cook plasticity and damage laws using a combined direct-inverse method. A direct calibration method for plasticity law is applied based on the literature-reported data of strain-stress curves from experimental tensile tests at different temperatures and strain rates. The triaxiliaty-dependent fracture parameters of the Johnson–Cook damage law at reference conditions of strain rate and temperature (d1, d2, and d3) are calibrated with the direct method based on new data of experimental evolution of computed average fracture strain with the average stress triaxiality. The validation is performed with numerical results from an accurate micromechanics-based Ti64 model. The inverse calibration method is used to determine the strain rate and temperature-dependent damage parameters (d4 and d5) through large strain simulations of uniaxial tensile tests. The numerical results, including average strain and necking profile at fracture, are then utilized to calculate stress triaxiality by the Bridgman criterion for adjusting parameters d4 and d5. The calibrated model yields a 2.1% error for plasticity and 3.4% for fracture predictions. The experimental and simulated load-bearing capacity using the micromechanics damage model differed by only 1%. This demonstrates that the SC11–TNT model of Ti64 is reliable for identifying the Johnson–Cook damage law through the accurate use of inverse methods. The hybrid calibration strategy demonstrates the potential capability of the identified Johnson–Cook model to accurately predict the design load-carrying capacity of Ti64 aerospace components under different deformation rates and temperatures while accounting for material damage effects.

Extreme massive hydraulic fracturing in deep coalbed methane horizontal wells: A case study of the Linxing Block, eastern Ordos Basin, NW China

Deep coal seams show low permeability, low elastic modulus, high Poisson’s ratio, strong plasticity, high fracture initiation pressure, difficulty in fracture extension, and difficulty in proppants addition. We proposed the concept of large-scale stimulation by fracture network, balanced propagation and effective support of fracture network in fracturing design and developed the extreme massive hydraulic fracturing technique for deep coalbed methane (CBM) horizontal wells. This technique involves massive injection with high pumping rate + high-intensity proppant injection + perforation with equal apertures and limited flow + temporary plugging and diverting fractures + slick water with integrated variable viscosity + graded proppants with multiple sizes. The technique was applied in the pioneering test of a multi-stage fracturing horizontal well in deep CBM of Linxing Block, eastern margin of the Ordos Basin. The injection flow rate is 18 m3/min, proppant intensity is 2.1 m3/m, and fracturing fluid intensity is 16.5 m3/m. After fracturing, a complex fracture network was formed, with an average fracture length of 205 m. The stimulated reservoir volume was 1 987×104 m3, and the peak gas production rate reached 6.0×104 m3/d, which achieved efficient development of deep CBM.

Microstructure evolution and mechanical property of melt-grown Al2O3/GdAlO3/ZrO2 eutectic ceramics prepared by laser directed energy deposition

Highly dense Al2O3/GdAlO3/ZrO2 eutectic ceramics are one-step additively manufactured by laser directed energy deposition technique under different scanning speed to investigate the inherent response relationship between processing parameter, microstructure, and mechanical property. During the layer-wise deposition process, planar-cellular transition occurs near the bottom of the molten pool, leading to the transformation of irregular eutectic structure into eutectic colony structure lengthened along the building direction, accompanied by the refinement of microstructure dimension. With the increase of scanning speed, the eutectic spacing decreases, and the initially irregular “Chinese script” eutectic ultimately transforms into hexagonally arranged rod-like eutectic structure induced by lamellar instability. The rod spacing is 1.136 times larger than the lamellar spacing. The mechanical property of the laser 3D-printed Al2O3/GdAlO3/ZrO2 eutectic ceramic is manifested as isotropic. The hardness increases with the refinement of the microstructure, while the fracture toughness decreases as the eutectic morphology transforms into rod-like structure. The averaged hardness and fracture toughness are 16.27 GPa and 3.39 MPa‧m1/2, respectively.

The effect of fracture growth rate on the fracture process zone of salt rock after heat treatment

The importance of rate on the mechanical properties of rocks has been widely acknowledged by numerous scholars. Currently, most researchers mainly focus on investigating the influence of loading rate, while there is limited research on the effects of fracture growth rate on mechanical properties such as fracture process zone (FPZ) and fracture toughness of rocks. In order to explore the impact of fracture growth rate on the mechanical properties of rocks, this study conducted three-point bending pure I-mode fracture experiments on salt rocks at temperatures ranging from ambient to 700 °C using different quasi-static loading rates (0.02–2 mm/min). Meanwhile, digital image correlation (DIC) technology was employed to monitor displacement and strain variations, identify and calculate the fracture growth rate and FPZ size, and subsequently compute the corrected fracture toughness. The study discussed the effects of temperature and fracture growth rate on the FPZ and fracture toughness of rocks. The following main conclusions are drawn based on the analyzed results: (1) Temperature and loading rate have a great influence on the onset of FPZ in salt rocks. The higher the temperature and loading rate, the earlier the onset of FPZ. (2) With the increase of the average fracture growth rate, the FPZ length at the peak load of rock salt and the modified fracture toughness increased continuously, and was divided into two stages, in the stage of the crack extension rate generated by the loading rate of 0.02 mm/min-1 mm/min grew faster, and the growth of the crack extension rate generated by the loading rate of more than 1 mm/min became slower. (3) The effect of temperature on the fracture parameters of rock salt is significant, the peak load moment FPZ length and fracture toughness first increase and then slowly decrease with increasing temperature from room temperature to 700℃. The inflection point is at 500℃, where the fracture toughness and FPZ length reach the maximum value. (4) As the loading rate increases the proportion of transgranular fracture in the rock salt fracture surface gradually rises, and the crack extension path becomes smoother and smoother.

Hot processing performance and fracture toughness control of AlxCrFeNiCu1.5 (x = 0, 0.2, 0.4, 0.6, 0.8) high entropy alloys

In order to develop high-entropy alloys with both good hot processing performance and fracture toughness, AlxCrFeNiCu1.5(x=0, 0.2, 0.4, 0.6, 0.8) alloys were designed and prepared. The alloy was firstly hot rolled by a twin-roll rolling device, and then the hot processing performance of the alloy under different Al contents was explored, whether the fracture toughness was at an ideal level, and if so, why it was at an ideal level. The results showed that the phase composition after hot rolling and annealing were two phases (face-centered cubic FCC and body-centered cubic BCC). With the increase of Al content, the FCC phase gradually transformed into BCC phase, and the increase of BCC phase led to the decrease of plasticity, which led to the decrease of hot processing performance. With the increase of Al content, the average fracture toughness value increased first and then decreased. Among them, the Al0.2CrFeNiCu1.5 and Al0.4CrFeNiCu1.5 alloys had the relatively better fracture toughness, which was because that the alloys had the appropriate proportion of FCC and BCC phases, and the strength and plasticity could achieve an ideal match. Among these alloys, the Al0.2CrFeNiCu1.5 alloy had the relatively better hot processing performance and ideal fracture toughness, and its average fracture toughness was 35.71 MPa·m1/2. And compared with Al0.2CrFeNiCu1.5 alloy, the Al0.4CrFeNiCu1.5 alloy had the worse hot processing performance, but it yielded the best fracture toughness, with an average value of 45.27 MPa·m1/2. In the crack propagation morphology, we found the main crack terminated at the notch upper part for the Al0.2CrFeNiCu1.5 alloy, suggesting that the material has good plasticity. And we also found crack multiple deflections and secondary cracking for the Al0.4CrFeNiCu1.5 alloy, which was helpful to improve the fracture toughness.

In Vitro Analysis of Outcome Differences Between Repairing and Replacing Broken Dental Restorations.

Objective In light of several advancements and considerations in endodontic dentistry, there still remains a need to comprehensively evaluate the outcome disparities between repairing and replacing broken dental restorations. This study aims to compare the effectiveness of repairing dental restorations versus replacing them, focusing on how each method affects the structural strength and longevity of the restorations. Methods The study included 60 freshly removed human maxillary premolars. Initial processing involved rigorous washing, descaling, and polishing of the teeth. To ensure preservation, the specimens were stored in sterile, distilled water. To occlude the root canals, a self-hardening composite resin was used, and the roots were coated with two coats of clear nail polish to prevent moisture penetration. A 245 carbide bur attached to a high-speed dental handpiece with air and water spray cooling produced standardized Class II cavities on the occluso-proximal surfaces. Each cavity had a buccolingual breadth of 2 mm, an occluso-cervical length of 4 mm, and a gingival boundary that was 1 mm coronal to the cement-enamel junction. Following this preparation, the teeth were randomly separated into three groups (Group A, Group B, and Group C), each containing 20 teeth. Results Our analysis showed that teeth with entirely replaced restorations had a higher average fracture resistance than those with repaired restorations. However, the difference in fracture resistance between the repair and replacement groups for each type of material was not statistically significant. Conclusion Based on the findings, repairing a dental restoration can be a conservative and less invasive alternative to a full replacement without a significant compromise in the restoration's ability to withstand fracture. Therefore, dental professionals might consider full restoration as a viable option, taking into account the need to preserve dental tissue as well as the restoration's durability and structural integrity.

Effect of in-situ nanoparticles induced by Ti addition on the microstructure and tribological properties of FeCrB alloys

Effect of in-situ nanoparticles (NPs) induced by Ti addition on the microstructure and tribological properties of FeCrB alloys has been investigated systematically by various advanced techniques. The results reveal that the TiC and TiB2 nanoparticles can be in-situ formed when adding Ti into the FeCrB alloys and they show great contribution to the microstructure refinement and tribological performance improvement of FerCrB alloys. With the gradual addition of Ti, the improvement effect of in-situ NPs increases initially and subsequently decreases. The JDF2 alloy (refers to FeCrB alloy containing 1.17 wt % Ti) shows the finest microstructure and the exceptional wear resistance. The average size and fracture toughness of primary borides are only 11.8 % of that in FeCrB matrix alloy (without Ti addition) and increase to 22.7 MPa∙m1/2, respectively. Moreover, the wear rate measures at 3.38 × 10−5 mm3/N·m, which is only 48.8% compared to that of FeCrB matrix alloy. The underlying wear mechanisms of FeCrB alloys have been discussed by unraveling the role of in-situ nanoparticles in the microstructure evolution, which belongs to adhesive wear and abrasive wear.

Determination of the Thickness and Fracture Toughness of Shale Interfacial Transition Zone Near Various Micromineral Aggregates Using Nano-Scratch Tests

Summary Heterogeneously distributed micromineral aggregates (MMAs) are common in shale reservoirs. The interfaces between these MMAs and the surrounding minerals significantly affect fracture propagation behaviors during shale oil exploitation. In this paper, the concept of interfacial transition zone (ITZ) between the MMAs (e.g., striped barite, pyrite, calcite, apatite blocks, and bedding plane) and the surrounding mineral in shale is introduced. Due to the small thickness of the ITZ, its thickness and mechanical properties are very difficult to determine by traditional standard methods. To address this issue, this paper proposes a method combining nano-scratch tests, scanning electron microscopy (SEM), and quantitative evaluation of minerals by SEM (QEMSCAN) techniques to investigate the thickness and fracture toughness of the ITZ near typical MMAs. The results show that the thickness of the ITZ determined by the transverse force FT and scratch depth (-d2) varies from 3.2 μm to 17.3 μm. In addition, the fracture toughness of both MMAs and ITZs is characterized by high heterogeneity ranging from 0.1 MPa·m0.5 to 2.1 MPa·m0.5. Moreover, a formula evaluating the fracture toughness of the ITZ is proposed taking into account the type and content of minerals in the ITZ. A strong linear relationship is observed between the thickness of the ITZ and the average fracture toughness ratio. In addition, a relationship is established between the fracture toughness of the ITZ and MMAs, and an evaluation equation is derived. This study is helpful for understanding the characteristics (i.e., mainly thickness and fracture toughness) of the ITZ within shales.