Bond Failure Research Articles

Effect of Chitosan Irrigant and Lubricating Gel on Bond Strength of Resin Sealer to Radicular Dentin: An In Vitro Study.

The adhesive strength of sealers to dentin is influenced by various factors, and the presence of a smear layer is among the critical variables. Chitosan, known for its dentin compatibility, has previously demonstrated a reduction in dentin change and resin sealer bond strength comparable to ethylenediaminetetraacetic acid (EDTA) when used as an irrigant and final rinse. The study investigates the impact of chitosan, used as both a lubricating gel and final rinse, on the push-out bond strength of resin sealer. Forty single-rooted premolar teeth, each with a fully formed root and a single root canal, were collected post-extraction. During canal preparation, 1 mlsodium hypochlorite (3%) was used for irrigation at every change ofinstrument, followed by applying specific chelating gel and final rinse for each experimental group. The groups included: Group 1 (17% EDTA chelating gel, final rinse with saline), Group 2 (17% EDTA chelating gel, final rinse with 17% EDTA solution), Group 3 (chitosan chelating gel, final rinse with saline solution), and Group 4 (chitosan chelating gel, final rinse with 0.2% chitosan solution), 10 specimens in each group.After obturation, specimens were sealed and incubated for a week at 37°C with 100% humidity. The universal testing machine was used for push-out tests, and specimens were examined using a scanning electron microscope (SEM) to identify various types of bond failure. Among the four groups, Group 2 exhibited the highest mean push-out bond strength (7.33 ± 0.26 MPa), followed by Group 4 (5.33 ± 0.25 MPa), Group 1 (4.61 ± 0.30 MPa), and Group 3 (2.94 ± 0.32 MPa). The variations in bond strength suggest a notable impact of the chelating agents and final rinse solutions on the resin sealer's interaction with dentin. The study concludes that the use of EDTA as both a lubricating gel and a final rinse significantly enhances push-out bond strength, outperforming chitosan in this study. Groups with saline as the final rinse (Group 1 and Group 3) exhibited the least bond strength, highlighting the importance of the final rinse in root canal therapy.

Experimental study on the bond-slip behavior of steel tube-coal gangue concrete

This study investigated the bond-slip behavior at the interface between steel tubes and coal gangue concrete, considering the coal gangue coarse aggregate replacement rate, the strength grade of coal gangue concrete, and the bond length as variable parameters. Eleven groups of push out tests were conducted on steel tube coal gangue concrete specimens. The bond slip curve and the longitudinal strain distribution curve of the steel tubes were obtained, and the effects of these parameters on bond strength were analyzed. The results showed that the load-slip curves at both the loading and free ends of the specimens were similar, with slip occurring earlier at the loading end. The regularity of the test curves in repeated experiments indicated that interfacial bond stress was primarily determined by friction in the later stages. The longitudinal strain of steel tubes was approximately exponentially distributed along their length. The interfacial bond strength increased with the increase of coal gangue aggregate replacement rate and was more pronounced in specimens with higher strength coal gangue concrete. Longer bond lengths resulted in greater bond failure loads, with a lower rate of increase in higher strength coal gangue concrete specimens compared to those with lower strength. Based on the three stage bond stress-slip relationship for steel tube-concrete, a bond-slip constitutive model for steel tube-coal gangue concrete was established. This provided a reference for mechanical analysis and interface performance design of steel tube-coal gangue concrete.

Calibration of models predicting the load-bearing capacity of bonded anchors using a genetic algorithm

The paper deals with the topic of resistance of bonded headless post-installed anchors to uncracked concrete, in particular with the calibration of selected models predicting their ultimate tensile load. In particular, the optimization of two models for predicting the tensile capacity of an anchor is investigated in this paper. First model is based on the determination of the ultimate capacity based on separated failure modes (failure of the extraction of concrete cone and the bond failure). The second optimised model, proposed in this paper, summarizes the effect of both of these parameters into a single exponential function. A model combining the effect of concrete strength and adhesive strength has the potential to better capture the true nature of failure in which both materials are involved. In order to compare these models, an extensive database of experimental results was compiled (including own experiments and also results from various authors). The calibration consisted in finding the most appropriate values of the individual input parameters of the models to fit the experimental results as closely as possible. The models for predicting the tensile capacity of anchors are multiparametric. Therefore, a method using elements of genetic algorithms was used for optimization, suitable for this purpose. Several possible statistical evaluation criteria were used for the evaluation of the fit of the models. The optimization of the models showed that the proposed model combining the effect of concrete strength and bond strength can be optimized to better fit the experimental results.

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 < 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.

Effect of Polywave and Monowave Light Curing Units on the Microtensile Bond Strength and Failure Types of Different Bulk-Fill Resin Composites: An in vitro Study.

This study aimed to evaluate the effects of polywave and monowave light-emitting diode curing units on the microtensile bond strength and failure types of three bulk-fill resin composites. This in vitro experimental study was performed on 180 microbars obtained from human third molars and were distributed into 12 groups according to the type of bulk-fill resin composite and the light-curing unit. Third molars were restored using Filtek One Bulk Fill Restorative, Tetric® N-Ceram Bulk Fill, and Opus Bulk Fill resin composites was light-cured with Elipar Deep Cure L and Valo in three modes: standard, high power, and extra power. Subsequently, microtensile analysis was carried out with a universal testing machine and the type of failure with an optical stereomicroscope. For statistical analysis, the Kruskal-Wallis H-test was used, with the Bonferroni post hoc test and Fisher's exact test, considering a significance of p<0.05. There were significant differences in the microtensile bond strength between the Filtek One Bulk Fill restorative and Opus Bulk-Fill (p = 0.042) when light was cured with the polywave unit at standard power. On the other hand, the Filtek One Bulk Fill Restorative and Opus Bulk Fill resins showed significant differences in microtensile bond strength when light was cured with the monowave unit compared with the polywave unit (p<0.05). The presence of alternative photoinitiator systems that are more reactive than camphorquinone produced higher microtensile bond strength in Tetric N-Ceram Bulk Fill and Opus Bulk Fill resins when light-cured with a high and standard polywave unit, respectively, compared to Filtek One Bulk Fill resins. Finally, Tetric N-Ceram Bulk Fill and Opus Bulk Fill resins had the highest percentage of mixed failures, while Filtek One Bulk Fill resin had adhesive failures, which was related to its lower microtensile bond strength.

Assessment of Nanosilver Fluoride Application on the Microtensile Bond Strength of Glass Ionomer Cement and Resin-modified Glass Ionomer Cement on Primary Carious Dentin: An In Vitro Study.

Nanosilver sodium fluoride (NSF) has recently gained popularity in dentistry as an alternative to silver diamine fluoride (SDF) due to its drawbacks of staining the tooth black and possibly causing soft tissue injury, which has been eliminated in NSF due to the nanoparticle size of silver. This study aims to assess the microtensile bond strength of glass ionomer cement (GIC) and resin-modified glass ionomer cement (RMGIC) with pretreatment of NSF on extracted primary carious teeth. Teeth were stored in 10% formalin. The roots were severed, and the pulp chambers were cleaned. The occlusal enamel was ground, reducing the dentin thickness by 1 mm. The specimens were covered with nail varnish, leaving only the area of flat dentin exposed. Caries were induced microbiologically by inoculating Streptococcus mutans. Group I-NSF with GIC restoration, group II-NSF with RMGIC restoration, group III-restoration with GIC, and group IV-restoration with RMGIC. After different surface treatments of the carious dentin were performed, each specimen was placed in the testing jig of a universal testing machine and stressed in tension at a crosshead speed of 1 mm/minute until bond failure was observed. They were air-dried and placed under a scanning electron microscope. The failure modes-adhesive, cohesive, and mixed failure were recorded for statistical evaluation. Maximum results of microtensile bond strength were seen in the pretreatment group with NSF sealant, followed by RMGIC restoration, and the least results were observed in the conventional GIC restoration group. Of all the types of failures in our study, adhesive was the maximum type. The microtensile bond strength of pretreatment with NSF showed higher values when compared to conventional restorations of GIC and RMGIC. The failure modes in each group were not significantly varied. Pretreatment with NSF will prevent secondary caries formation, and the restorations will also be stronger. Das A, Ramamurthy N, Srinivasan I, et al. Assessment of Nanosilver Fluoride Application on the Microtensile Bond Strength of Glass Ionomer Cement and Resin-modified Glass Ionomer Cement on Primary Carious Dentin: An In Vitro Study. Int J Clin Pediatr Dent 2024;17(5):565-569.

Microtensile Bond Strength and Failure Mode of Different Universal Adhesives on Human Dentin

AimThe aim of this study was to compare the microtensile bond strength (µTBS) and failure mode of 4 different universal adhesive systems (UAs) on human dentin. Materials and methodsThe study sectioned the occlusal thirds of 32 human third molars and divided them into 4 groups based on the adhesive system used. Group A: Palfique Universal Bond, Group B: Single Bond Universal, Group C: All-Bond Universal, and Group D: One Coat 7 Universal. The specimens underwent a 10,000-cycle thermocycling ageing process prior to testing (n = 32). Afterwards, 8 beams were obtained per group and subjected to µTBS testing using a digital universal testing machine at a speed of 1 mm/min. The microtensile bond strength values were analysed in Megapascals (MPa), and the failure mode was evaluated using a stereomicroscope. Welch's parametric ANOVA with robust variance and the Games-Howell post hoc test were used for µTBS comparisons, and Fisher's exact test was used to determine the association between adhesive type and failure mode. The significance level was set at P < .05. ResultsGroup D showed a significantly higher µTBS than groups A (P < .001) and B (P < .001), but no significant difference was observed with group C (P= .075). Furthermore, groups B and C showed significantly higher µTBS than group A (P< .001 and P < .001, respectively), but there was no significant difference between groups B and C (P = .132). Additionally, group A exhibited a significant association with an adhesive failure mode (P < .05), whereas groups B, C, and D were significantly associated with a mixed failure mode (P < .05). ConclusionThe One Coat 7 Universal adhesive system showed higher microtensile bond strength values and higher chemical interaction with dentin compared to Palfique Universal Bond and Single Bond Universal. However, no significant differences were observed compared to All-Bond Universal.

FATIGUE BOND LIFE OF REINFORCED CONCRETE BEAMS WITH LOW REINFORCEMENT CORROSION

Corrosion in reinforced concrete elements can result in a decrease in cross-sectional area and loss of bond between steel and concrete. The cumulative effects of fatigue loading can exacerbate the adverse impact on the bond characteristics between steel and concrete. In this study, the impact of reinforcement corrosion on the fatigue bond life of reinforced concrete members using lap-splice specimens is investigated. The beams are designed such that the failure of the control specimen occurs due to bond failure in the lap-splice region. Stirrups are provided in the lap-splice region to consider the influence of stirrup confinement on bond behavior. The longitudinal rebars and stirrups in the lap-splice region are subject to accelerated corrosion using the impressed current technique, respectively achieving approximately 5% and 15% mass loss. Subsequently, the beam specimens are tested under four-point loading, such that the lap-splice region falls under a constant moment zone. Under monotonic loading, the control specimen experiences abrupt failure due to bond failure. In fatigue loading, the corroded specimen exhibits a significant reduction of 98% in its fatigue life.

Study on the ultrasonic cavitation damage to early atherosclerotic plaque

Ultrasonic cavitation can damage surrounding material and be used for destruction of the target tissue. In this paper, we investigated the interaction between atherosclerotic plaque (AP) and cavitation bubbles to determine whether the mechanical effect of cavitation damage could be potentially useful in therapy for treating atherosclerotic plaques. A two-bubble–fluid–solid model was established to study the dynamic behavior of bubbles near the AP and the AP damage by ultrasound-induced cavitation. A low-intensity focused ultrasound (LIFU) transducer was used for testing cavitation-based AP damage. We found that the nonlinear oscillation of bubbles causes the relative positions of the bubbles to shift, either toward or away from one another, these phenomena lead to changes in the bond failure rate between the fiber bundles, and the value of BRF exhibits an upward trend, this is the reason why the fibers suffered from reversible stretching and compressing. However, the AP damage is irreversible and diminishes as the number of cycles in the ultrasonic burst. It appears that the bigger the radii, regardless of whether the bubble (3 − i)’s and bubble i's radii are equal, the greater the AP damage. Ultrasonic cavitation therapy may not be appropriate for advanced AP patients, and the calcified tissue has a greater impact on the stability of the plaque. The damage area should be strictly selected. Additionally, the tissue damage phenomenon was found in experimental results. This work shows that the severity of AP damage is correlated with acoustic parameters and the surrounding environment from both simulation and experimental perspectives. The results show that ultrasonic cavitation may provide a new choice for the treatment of AP.

FATIGUE BOND LIFE OF REINFORCED CONCRETE BEAMS WITH LOW REINFORCEMENT CORROSION

Corrosion in reinforced concrete elements can result in a decrease in cross-sectional area and loss of bond between steel and concrete. The cumulative effects of fatigue loading can exacerbate the adverse impact on the bond characteristics between steel and concrete. In this study, the impact of reinforcement corrosion on the fatigue bond life of reinforced concrete members using lap-splice specimens is investigated. The beams are designed such that the failure of the control specimen occurs due to bond failure in the lap-splice region. Stirrups are provided in the lap-splice region to consider the influence of stirrup confinement on bond behavior. The longitudinal rebars and stirrups in the lap-splice region are subject to accelerated corrosion using the impressed current technique, respectively achieving approximately 5% and 15% mass loss. Subsequently, the beam specimens are tested under four-point loading, such that the lap-splice region falls under a constant moment zone. Under monotonic loading, the control specimen experiences abrupt failure due to bond failure. In fatigue loading, the corroded specimen exhibits a significant reduction of 98% in its fatigue life.

Physical, antimicrobial, and release profiles of orthodontic adhesives modified with chlorhexidine and cetylpyridinium chloride

The aim of the present study was to evaluate the properties (physical, antimicrobial, and release profiles) by using modified orthodontic adhesives on extracted teeth. Three primers, Transbond (Tx), Transbond-Chlorhexidine (Tx-CHx), and Transbond-Cetylpyridinium chloride (Tx-CTP), containing antibacterial agents CHx and CTP, were tested against Streptococcus mutans (Sm) in planktonic and biofilm phases. Their antimicrobial activities (biofilm and growth assays), affected by water aging, were analyzed along with shear bond strength and mode of fracture after bonding brackets onto bovine incisors. Tx-CHx demonstrated superior antimicrobial activity against in both planktonic and biofilm states, completely inhibiting their growth and biofilm formation. This effectiveness persisted after thermocycling. Conversely, Tx-CTP showed a positive outcome against microbial activity compared to Tx. Shear bond strength (SBS) (Tx–11.21±1.72; Tx-CTP–12.48±2.50; Tx-CHx–11.57±2.28) and bond failure interface showed no significant differences among the three primers. Adding CHx and CTP to an orthodontic primer could potentially safeguard enamel from demineralization without negatively impacting its structural characteristics.

Experimental analysis of the effect of bar anchorage length on bond behavior in pull-out test

The article presents bond tests performed using the pull-out method. The experiments were designed to evaluate the effect of anchorage length on the bond in this test. The analysis shows that the length of the bar-concrete interface significantly influences the bond behavior. It determines the type of bond failure, affects the distribution and value of stresses in the bar, and projects the bond-slip curve, which is a key result of the pull-out test

Mesoscopic Analysis of Fatigue Damage Development in Asphalt Mixture Based on Modified Burgers Contact Algorithm in Discrete Element Modeling.

This study is aimed at examining the mesoscopic mechanical response and crack development characteristics of asphalt mixtures using the three-dimensional discrete element approach via particle flow code (PFC). The material is considered an assembly of three phases of aggregate, mortar, and voids, for which three types of contact are identified and described using a modified Burgers model allowing for bond failure and crack formation at contact. The laboratory splitting test is conducted to determine the contact parameters and to provide the basis for selecting three different load levels used in the indirect tensile fatigue test and simulation. The reliability of the simulation is verified by comparing the fatigue lives and dissipated energies against those from the test. Under cyclic loading, the internal tensile and compressive force chains vary dynamically as a response to the cyclic loading; both are initially concentrated beneath the top loading strip and then extend downward along the loading line. The compressive chains are oriented roughly vertically and develop an elliptic shape as damage grows, while the tensile chains are mostly horizontal and become denser. An analysis based on the histories of the numbers of different contact types indicates that damage mainly originates from bond failures among the aggregate particles and at the aggregate-mortar interfaces. In terms of location, cracking is initiated below the loading point (consistent with observations from the force chains) and propagates downward and laterally, leading to the macrocrack along the vertical diameter. The findings provide a mesoscopic understanding of the fatigue damage initiation and propagation in asphalt mixture.

XGBoost algorithm based estimation of near surface mounted FRP rod-to-concrete bond strength and failure mode

Using fiber-reinforced polymer (FRP) in reinforced concrete (RC) structures can mitigate the colossal repair costs due to reinforcing steel corrosion. Hence, FRP rod/bar is gaining wider applications in diverse RC structures as a partial or full replacement for steel rebar. The FRP rod-to-concrete interfacial bond is pivotal in transferring stresses from concrete to FRP rods. This study develops a novel prediction model to estimate the near surface mounted FRP rod-to-concrete bond strength as well as the failure type using five machine learning (ML) algorithms, namely, linear regression, decision tree, gradient boosting tree, random forest, and extreme gradient boosting (XGB). The performance of the developed models was compared with that of four bond strength design guidelines and one analytical model. A database comprising 416 experimental datasets was constructed and used for model training and validation. Based on statistical performance metrics, the precision of the XGB algorithm was superior to that of the other ML models, design guidelines, and analytical model. Feature importance analysis based on the SHapley Additive exPlanations theory and partial dependence plot was performed. The results show that the bond length had the most significant influence on the bond strength, followed by the tensile strength of the FRP composite, diameter of the FRP rod, compressive strength of concrete, and elastic modulus of the FRP composite. A graphical user interface was developed and offers a user friendly, free access, and simple tool for estimating the bond strength and failure type of FRP rods in concrete.

Numerical analysis of the local damage of RC beams under close‐in explosions based on the calibrated Karagozian &amp; Case (K&amp;C) concrete model

AbstractLimited research has been carried out to investigate the local damage features of reinforced concrete (RC) beams under close‐in explosions. To better capture the local damage features of rectangular cross‐sectional RC beams, a numerical study on the RC beams subjected to close‐in explosions based on the calibrated Karagozian &amp; Case (K&amp;C) concrete model was conducted in LSDYNA. First, a systematic calibration of the K&amp;C model for concrete was performed in the single‐element numerical analysis. Calibration of the K&amp;C model consists of parameter determination for the new strength surfaces, modification of the damage function to better feature the tensile behavior of concrete, elimination of the element size effect by introducing an element size factor and determination of the scaled damage factors. The new strength surfaces are verified and determined through both the approximation calculation method and the parameter fitting method. And the damage function was modified by reducing the termination of λ to better characterize the brittleness of concrete and feature the tensile failure. A comparison between the numerical results and the corresponding experimental results demonstrates that the calibrated K&amp;C model and established FEM model of RC beams subjected to close‐in explosions can well characterize the local damage features of RC beams. On this basis, a further parameter analysis on the factors influencing the local damage response of RC beams was conducted by considering reinforcement details (stirrup spacing and longitudinal reinforcement diameter) and charge details (charge mass and aspect ratio). Results show that the close‐in explosions destroyed the concrete corners in the blast surface with shear stress first and the side shear failure of concrete corners weakens the concrete core strength and contributes to the greater loss of concrete core. Rear spalling damage was initially caused by the bond failure between the tensile longitudinal reinforcement and the surrounding concrete. Furthermore, increasing stirrup spacing, tensile longitudinal reinforcement diameter, and charge mass contribute to the increase in local damage sizes.

Evaluation method of the synergistic service performance between ultrahigh-performance concrete and normal strength concrete based on the parameter of environmental equivalent force ratio

This study investigated the synergistic service performances of ultrahigh-performance concrete (UHPC) and normal-strength concrete (NSC). Restrained specimens used in this study were designed to assess the non-equivalent deformation of a substrate and UHPC under specific service conditions and shrinkage. Various UHPC repair materials characterized by different shrinkage deformation gradients were developed using expansive agents and lightweight aggregates. The study explored the effects of shrinkage on the synergistic service properties of UHPC-NSC. In addition, the bond fatigue performance of UHPC-NSC was investigated, and a bond fatigue-life equation was formulated. Under static loads and a stress ratio of 0.9, specimens exhibited both substrate and bond failures. By contrast, specimens under stress ratios of 0.8 and 0.7 displayed substrate failure. The synergistic effect of a 10 % dosage of expansive agent and a 15 % dosage of lightweight aggregate resulted in a 67.2 % reduction in UHPC shrinkage after 28 d. Internal stress derived from the non-equivalent deformation of the substrate and UHPC due to shrinkage was quantified. A reduction in UHPC shrinkage led to a 33.0–67.3 % decrease in tensile stress for repair materials. Internal stresses in the UHPC-NSC under alternating environments, including wet–dry, hot–cool, and freeze–thaw cycles, were calculated, where the ratio of internal stress to interfacial strength was defined as the interfacial stress-intensity ratio. This study presents an evaluation method for the synergistic service performance of UHPC-NSC based on an environmental equivalent-force ratio, thereby providing guidance for practical concrete-repair service-life design.

The Effect of Adding Various Antibiotics on the Push-out Bond Strength of a Resin-based Sealer: An In Vitro Study.

This study aimed to compare the bond strength of AH Plus sealer to root canal dentin when used with or without various antibiotics including amoxicillin, clindamycin, and triple antibiotic mixture (TAM). A total of 80 single-rooted extracted human teeth were instrumented and obturated with gutta-percha and four different sealer-antibiotic combinations (n = 20). Group I: AH Plus without any antibiotics, Group II: AH Plus with amoxicillin, Group III: AH Plus with clindamycin, and Group IV: AH Plus with TAM. After seven days, the roots were sectioned perpendicular to their long axis and 1 mm thick slices were obtained from the midroots. The specimens were subjected to a push-out bond strength test and failure modes were also evaluated. Data was analyzed using Kruskal-Wallis and Dunn's post hoc tests. Group IV had significantly higher bond strength compared to other groups (p ≤ 0.05). No significant differences were found between other groups. While the sealer-antibiotic groups predominantly showed cohesive failure modes, the control group displayed both cohesive and mixed failure modes. Within the limitations of this study, the addition of TAM increased the push-out bond strength of AH Plus. Amoxicillin, clindamycin, or TAM can be added to AH Plus for increased antibacterial efficacy without concern about their effects on the bond strength of the sealer. How to cite this article: Adl A, Shojaei NS, Ranjbar N. The Effect of Adding Various Antibiotics on the Push-out Bond Strength of a Resin-based Sealer: An In Vitro Study. J Contemp Dent Pract 2024;25(3):231-235.

Parametric study for structural performance of spliced hybrid deck beams with UHPC cast in place joints

Splice beams are considered a solution for some difficults in bridge construction and a method for repairing damaged beams. One of the most challenging aspects of this technique is avoiding bond failure between the spliced members. In this study, ultra-high performance concrete (UHPC) was used to splice three beam segments due to its superior performance. This paper investigate the effects of some parameters on the spliced beams by Finite Element Method using computer program ABAQUS. The study have two approaches, first one, a validation study to generate model agree with experimental test results of seven specimens were tested under three bending point load. The main variables being the depth of the joint, the presence of a shear key in the joint, the hybridization of reinforcement, and the addition of dowels in the joint. The model was simulated and achieved good convergence when compared with experimental results, considering the load-deflection response and failure mode. The second approach that investigated various parametric studies, such as reverse cyclic load, repeated cyclic load, thickness of the deck, type of interface joint, reinforcement ratio, strengthening by UHPC layer, and the loading pattern.

Study on the Tensile and Shear Performances of Fully Precast Partially Composite Floor Slab Joints

This study explored the tensile and shear characteristics of fully prefabricated partially composite floor slab joints through the design and testing of two tensile specimens, three steel–concrete specimens, and three concrete–concrete shear specimens. These tests aimed to evaluate how various connection designs influence the joints’ load-bearing capabilities and failure patterns. The findings revealed that the tensile specimens predominantly showed bond failures at the interface of the precast and cast-in-place layers, accompanied by rebar pull-out. Incorporating reinforcing bars or sleeves was found to potentially increase their ultimate load-bearing capacity by about 20%. The shear failures in the steel–concrete specimens were primarily due to interactions between the steel beam and adjacent composite slab, whereas the concrete–concrete specimens mostly underwent local crushing at the load application point and failure at the bonding interface. These observations affirmed the accuracy of the existing methods for calculating tensile and shear strengths, offering vital insights for the architectural design and construction of such floor joints.

Stress Analysis on Mesiolingual Cavity of Endodontically Treated Molar Restored Using Bidirectional Fiber-Reinforced Composite (Wallpapering Technique).

Endodontically treated teeth (ETT) undergo extensive structure change and experience high stress during biomechanical function. Stress distribution is influenced by the restoration material and the type of bond between material and tooth structure. The selection of materials that can distribute stress will affect the resistance and retention of ETT to mastication forces, thus biomechanical functions were achieved. Composite has mechanical properties similar to dentin, it can transmit and distribute stresses throughout the tooth surface. The disadvantage of composites in large cavities is their lack of toughness. The addition of fiber to composites can increase their toughness. This research is to determine the stress distribution of a fiber-reinforced composite made of polyethylene and e-glass on the mesiolingual cavity of ETT. A three-dimensional model of the mandibular molar was prepared for cavity preparation and the formation of restorations using SolidWorks 2021. The models were analyzed with Abaqus 2020 to determine stress concentrations after given vertical and oblique loading. The maximum and minimum principal stress data were obtained to assess material resistance and interfacial damage criterion. Polyethylene fiber shows a more homogeneous stress distribution because the modulus of elasticity is close to the dentin and has a thickness that can reduce the volume of the composite. The E-glass shows the stress concentration on the circumferential fiber and cavity floor. The stress distribution of fiber-reinforced composite on the buccolingual cavity of ETT using the finite element method did not show structural failure in the polyethylene group because the maximum and minimum principal stresses were lower than the strength of the material. Interfacial bond failure occurs at the enamel portion. The maximum and minimum principal values of e-glass indicate structural failure in the circumferential fiber and the base fiber because the stress exceeds the strength of the material. Interfacial bond failure occurred on the circumferential and the cavity floor.