Fracture Strength Values Research Articles

Micromechanical characteristics of titanium alloy (Ti-6Al-4V) made by laser powder bed fusion using an in-situ SEM micropillar compression technique

While titanium alloy (Ti-6Al-4V) made by laser powder bed fusion (L–PBF) exhibits complex deformation behaviors, its important micromechanical properties in relation to loading directions are not fully understood. This research aims to investigate the micromechanical behaviors of printed L–PBF Ti-6Al-4V alloys under vertical (i.e., the loading direction perpendicular to printed layers) and horizontal (i.e., the loading direction parallel to printed layers) compressions using in-situ scanning electron microscopy (SEM) micropillar techniques. Ti-6Al-4V alloys were L-PBF-printed using a 45° rotate scanning strategy with vertical and horizontal build directions. The microstructures of the two alloys were analyzed using the SEM with energy-dispersive X-ray spectroscopy (EDS). The titanium alloy micropillars were produced using focused ion beam (FIB) milling in the SEM. In-situ SEM micropillar compressions were conducted using a flat diamond indenter. Vertical alloy had smaller cross-patterned finer α′ martensite than horizontal one. While both vertical and horizontal micropillars showed elastic-plastic behaviors, the former had significantly higher yield, fracture, and compression strength values, as well as resilience and toughness, than the latter, leading to the formation of favorable shear bands. Both micropillars exhibited ductile fractures but had distinct failure mechanisms. The ductile fracture in the vertical micropillars was due to strain hardening, large plastic deformation, and shear band formation, while the ductile fracture in the horizontal ones was attributed to compression-induced bending and plastic buckling. The micromechanical characteristics of L–PBF Ti-6Al-4V materials provides an important insight into the small-scale deformation and failure mechanisms of the alloys influenced by loading directions.

The Influence of Different Pontic Designs on Fracture Resistance of Implant-supported Fixed Partial Dentures Anchored in Polyurethane Simulating Bone-blocks of Two Different Densities: An In Vitro Study.

This study aimed to evaluate the fracture resistance of implant-supported fixed partial prostheses fabricated from monolithic zirconia with different pontic framework designs and anchored in different bone-like simulation models of two different densities. A total of 60 implants were anchored in two different in vitro bone simulation models of two different densities, namely, solid polyurethane foam blocks, 20 and 10 pounds per cubic foot (PCF) to construct implant-supported fixed partial dentures (FPDs), the pontic constructed to replace missing second premolar and first molar. Thirty models were constructed and then divided into two groups according to anchoring material D2 (n = 15) and D3 (n = 15). Each group of models was subdivided into three groups according to pontic design (n = 5). Each model was tested against fracture in a universal testing machine. The data were analyzed with a two-way univariate ANOVA and Tukey HSD test (α = 0.05). The results were statistically analyzed, and the values were considered significant at p≤0.05. The findings showed that neither change in pontic design nor change in bone type has a significant influence on the fracture resistance of the prostheses (p > 0.05). All the tested materials fell within the acceptable range for functioning under mastication, with a slight change in resistance when the pontic design was changed. Zirconia is considered the material of choice when planning implant-supported FPDs because of its high fracture strength values. Within the limitations of this study, the pontic design and synthetic polyurethane bone-simulating model had no effect on the fracture resistance of four-unit implant-supported FPDs. This study postulated that any pontic design could be used in four units of implant-supported FPDs according to functional and aesthetic needs, as long as the histological nature of the alveolar bone falls within the D2 or D3 bone type. How to cite this article: Othman MS, Abu-Eittah MRH. The Influence of Different Pontic Designs on Fracture Resistance of Implant-supported Fixed Partial Dentures Anchored in Polyurethane Simulating Bone-blocks of Two Different Densities: An In Vitro Study. J Contemp Dent Pract 2024;25(7):684-690.

Evaluation of asphalt anti-cracking performance of SBS polymer with SCB method and deep learning

In recent years, there have been unprecedented developments in artificial intelligence. Object detection, voice recognition, face recognition etc. are some of the artificial intelligence applications. In this study, an auxiliary method for the automatic detection of cracks, one of the main deterioration problems on highways, is proposed. The crack formation of hot mix asphalts is investigated with an image processing method modeled with Attention SegNet architecture. Styrene-butadiene-styrene (SBS), the most widely used additive in bitumen modification, was used at 2 %, 3 %, and 4 % ratios to modify 50/70 bitumen. Semi-circular asphalt specimens obtained with SBS modified bitumen were subjected to a semicircular bending (SCB) test and fracture performance was investigated. The effects of different temperature, notch size and additive on crack detection performance are evaluated. In the experimental study, maximum load, fracture energy, fracture toughness (KIC) values were obtained at low temperature, and resistance values against crack propagation were obtained by applying the J-integral method at intermediate temperature. The results demonstrated that with the addition of SBS, the fracture strength and maximum load values increased at each temperature value, with the 4 % SBS mixture offering the highest performance. Moreover, the image segmentation performed with SegNet provided high accuracy and precision values for cracks. It was observed that the accuracy values of the image processing methods decreased at low temperature, while at high temperature, higher accuracy values were obtained as the cracking rate.

Experimental and numerical study on the effect of friction between crack faces on fracture parameters of hot mix asphalt concrete

This article investigates the effect of friction between crack faces in ASCB (asymmetric semi-circular bend) specimen on fracture parameters of hot mix asphalt concrete. To achieve this, fracture tests were conducted on ASCB specimens containing cracks with different angles (0, 10, 20, 30, and 40°). In addition to the fracture tests, friction tests were also performed by designing a simple fixture. Subsequently, finite element analyses were carried out, and friction coefficients between crack faces were calculated based on the results of fracture and friction tests. Furthermore, two fracture criteria, ASED (average minimum strain energy density) and MTS (maximum tangential stress), were examined under two different scenarios: assuming zero-friction and non-zero friction between crack faces to predict fracture load and fracture strength. The fracture tests showed that with an increase in the crack angle, the fracture load initially decreased up to the crack angle of 20°, and then increased. Furthermore, the friction tests revealed that an increase in the normal load led to an increase in the friction coefficient. As per finite element results, the crack face contact occurred at a crack angle of 13.1°. Hence, crack faces in the ASCB specimens with the crack angles of 20, 30, and 40° had friction, which significantly affected the fracture parameters. The results also indicated that the average error values for the MTS and ASED criteria compared to the experimental results were 22.8 % and 18.8 %, respectively, when the friction` between crack faces is ignored, and 12.4 % and 4.0 % for the scenario that the friction effect is taken into account. The ASED criterion demonstrated higher accuracy than MTS criterion. Additionally, the average error value of fracture strength predicted by the ASED criterion with assuming non-zero friction was 4 %, indicating good predictive accuracy for fracture strength.

Influence of viscosity and fiber reinforcement of resin composite on fracture strength and failure mode of restored molars.

To evaluate the fracture behavior of human molars with extensive MOD restorations using short-fiber-reinforced resin composite of varying viscosities. Human molars were randomly divided into seven groups (n = 12): intact teeth (control); restoration using conventional high-viscosity resin composite without (Filtek Z350XT, 3M) or with fibers (everX Posterior, GC); conventional low-viscosity resin composite without (Filtek Supreme Flowable, 3M) or with fibers (everX Flow Dentin Shade, GC); bulk-fill low-viscosity resin composite (Filtek Bulk Fill Flow, 3M) or with fibers (everX Flow Bulk Shade, GC). Restorations were performed on extensive MOD preparations, following the manufacturers' recommendations for each material. Specimens underwent fracture strength testing (N) and fracture pattern (%) categorized as repairable, possibly repairable, or non-repairable. Results were analyzed using a generalized linear model (N) and Fisher's exact test (%), with α = 0.05. Restorations performed with high-viscosity materials showed fracture strength values similar to the control and higher than those of restorations using low-viscosity resin composites (p < 0.0001), except for the bulk-fill low-viscosity resin composite with fibers (p > 0.05). Teeth restored using low-viscosity resin composite with fibers showed a higher % of repairable and possibly repairable fractures than the control (p = 0.0091). The viscosity of materials mediated the fracture strength, with restorations using high-viscosity resin composites promoting values similar to the intact tooth; however, the presence of fibers influenced the fracture pattern. Teeth with MOD cavities restored with high-viscosity resin composites showed similar fracture strength to intact teeth. Fiber-reinforced low-viscosity resin composite for the base of restoration resulted in a more repairable/possibly repairable fracture pattern.

In Vitro Assessment of a New Block Design for Implant Crowns with Functional Gradient Fabricated with Resin Composite and Zirconia Insert.

This study aims to evaluate and compare the mechanical resistance, fatigue behavior and fracture behavior of different CAD/CAM materials for implant crowns. Eighty-eight implant crowns cemented-screwed with four sample groups: two monolithic G1 Zirconia (control) and G3 composite and two bi-layered G2 customized zirconia/composite and G4 prefabricated zirconia/composite. All static and dynamic mechanical tests were conducted at 37 °C under wet conditions. The fractographic evaluation of deformed and/or fractured samples was evaluated via electron microscopy. Statistical analysis was conducted using Wallis tests, which were performed depending on the variables, with a confidence interval of 95%, (p < 0.05). The Maximum Fracture Strength values displayed by the four groups of samples showed no statistically significant differences. The crown-abutment material combination influenced the failure mode of the restoration, transitioning from a fatigue fracture type located at the abutment-analog connection for monolithic materials (G1 and G3) to a brittle fracture located in the crown for bi-layered materials (G2 and G4). The use of layered crown materials with functional gradients appears to protect the crown/abutment connection area by partially absorbing the applied mechanical loads. This prevents catastrophic mechanical failures, avoiding long chairside time to solve these kinds of complications.

The effect of restorative material selection and cementation procedures on the durability of endocrowns in the anterior teeth: an in-vitro study

ObjectiveTo investigate the fracture resistance and failure modalities of anterior endocrown restorations fabricated employing diverse ceramic materials, and bonded using various cementation methodologies.Materials and methodsForty maxillary central incisors were divided into two main groups based on the ceramic materials used; GroupI (Zir): zirconia endocrwons (Zolid HT+, Ceramill, Amanngirrbach) and GroupII (E-Max): e-max endocrowns (IPS e.max CAD, Ivoclar Vivadent). Both groups were further split into two subgroups depending on the cementation protocols; subgroup IA “ZirMDP”: endocowns cemented with MDP primer + MDP resin cement, subgroup IB (ZirNon-MDP): cemented with MDP primer + non-MDP resin cement, subgroup IIA (E-maxMDP): cemented with MDP primer + MDP resin cement, subgroup IIB (E-maxNon-MDP): cemented with MDP primer + non-MDP resin cement. (n = 10/subgroup). Endocrowns were manufactured using CAD/ CAM. Teeth were subjected to 10,000 thermal cycles. The fracture test was performed at 45o with a palatal force direction until the fracture occurred. Test results were recorded in Newton. The failure mode was examined using a stereomicroscope. A One-way ANOVA test was utilized to compare different groups regarding fracture strength values. Tukey`s Post Hoc was utilized for multiple comparisons.ResultsThe comparative analysis of fracture strength across the diverse groups yielded non-significant differences, as indicated by a p-value exceeding 0.05. Nonetheless, an observable trend emerged regarding the mode of failure. Specifically, a statistically significant prevalence was noted in fractures localized within the endocrown/tooth complex below the cementoenamel junction (CEJ) across all groups, except for Group IIB, “E-max Non-MDP,” where fractures within the endocrown/tooth complex occurred above the CEJ.ConclusionsCombining an MDP-based primer with an MDP-based resin cement did not result in a significant effect on the anterior endocrown fracture strength.Clinical relevanceRegardless of the presence of the MDP monomer in its composition, adhesive resin cement achieved highly successful fracture strength when used with MDP-based ceramic primers. Additionally, ceramic materials exhibiting elastic moduli surpassing those of dentin are discouraged due to their propensity to induce catastrophic fractures within the tooth structure.

The influence of zirconia and fiber posts with different lengths on the fracture strength of maxillary central incisors restored with zirconia crowns: an in vitro study.

Endodontically treated teeth are more susceptible to fractures than vital teeth because of significant coronal and radicular dentin loss during endodontic therapeutic procedures. The objective of the present in vitro study was to estimate and compare the influence of the post length and type on the fracture strength of endodontically treated maxillary central incisors. Sixty extracted human maxillary central incisors were decoronated 2 mm above the cementoenamel junction. The teeth were selected and subjected to standard endodontic treatment, resulting in three groups with different preparation lengths: 5, 7.5, and 10 mm. Each group was randomly divided into two subgroups according to the post type: zirconia or fiber. After appropriate surface treatment, they were cemented with adhesive resin cement and restored with zirconia crowns. Thermocycling (5°C to 55°C, 60 s, 1500 cycles) was performed after cementing the zirconia crowns onto each tooth. Prepared samples were subjected to a compressive static load of 0.5 mm/min, at an angle of 130 degrees to the long axis of the roots, using a universal testing machine (Matest) at a crosshead speed of 0.5 mm/min, until fracture. The significance of the results was assessed using two-way analysis of variance (ANOVA) and the Tukey-Kramer test (α = 0.05). The ANOVA analysis indicated significant differences (P < 0.05) between the groups. The Tukey-Kramer test revealed no significant differences among the zirconia posts with lengths of 5 mm (26.5 N ± 13.4), 7.5 mm (25.2 N ± 13.9), and 10 mm (17.1 N ± 5.2). Also, in the fiber post group, there was no significant difference when the posts with lengths of 7.5 mm (13.4 N ± 11.0) were compared with those of 5 mm (6.9 N ± 4.6) and 10 mm (31.7 N ± 13.1). The 10-mm-long post displayed superior fracture strength, and the 5-mm-long post showed significantly lower mean values (P < 0.001). The fracture strength of zirconia posts (with lengths of 5 and 7.5 mm) was found to be significantly higher than that of fiber posts (with lengths of 5 and 7.5 mm). The 10-mm-long fiber post group demonstrated significantly higher fracture strength values, and the 5-mm-long fiber post group showed the lowest values for the force resulting in root fracture; these groups were significantly different from each other (P < 0.001). The fracture strength analysis with a universal testing machine is the only method that enables the estimation of the differences between zirconia and fiber posts with different lengths in endodontically treated teeth.

Effect of Long Glass Fiber Orientations or a Short-Fiber-Reinforced Composite on the Fracture Resistance of Endodontically Treated Premolars.

This study aimed to evaluate the effect of direct restorations using unidirectional glass fiber orientations and a short-fiber-reinforced composite (SFRC) on the fracture resistance of endodontically treated premolars with mesio-occluso-distal cavities. Ninety double-rooted premolars were selected. Fifteen teeth were left intact/as a control group. The endodontic treatment and cavity preparations of seventy-five teeth were performed and divided into five experimental groups: Resin composite (RC), modified transfixed technique + RC, circumferential technique + RC, cavity floor technique + RC, and SFRC + RC. All teeth were fractured under oblique static loading at a 30° angle using a universal testing machine. The fracture patterns were observed and classified. Data were analyzed with one-way analysis of variance, Pearson chi-square, and Tukey HSD post hoc tests (p = 0.05). The highest fracture strength values were obtained in intact teeth (599.336 N), followed by modified transfixed + RC treated teeth (496.58 N), SFRC + RC treated teeth (469.62 N), RC (443.51 N), circumferential + RC treated teeth (442.835 N), and cavity floor + RC treated teeth (404.623 N) (p < 0.05). There was no significant difference between the RC and the circumferential technique + RC (p > 0.05). Unrepairable fractures were observed at low rates (20%) in the modified transfixed + RC and SFRC + RC teeth, and at higher rates in RC (73.3%), cavity floor + RC (60%), and circumferential + RC (80%) teeth. The application of an SFRC or the modified transfixed technique yielded an improved fracture strength and the fracture pattern of ETPs being restored with a universal injectable composite.

Impact of Various Cavity-Preparation Designs on Fracture Resistance and Failure Mode of CAD/CAM Fabricated Ceramic Inlays and Onlays

In recent years, CAD/CAM technology has allowed indirect ceramic restorations to become a part of everyday chairside clinical practice. Therefore, the impact of different cavity-preparation designs on the fracture resistance of CAD/CAM fabricated ceramics was assessed in this study. Three designs of cuspal covering (none, palatal, and entire) and two widths of the occlusal isthmus (75% and 100% of the intercuspal distance) were used for the preparation of inlays and onlays to form six groups (n = 10/group). Moreover, thermomechanical cyclic loading was applied to every tooth under a chewing simulator. A universal testing machine was used to measure each group’s fracture resistance. The tested specimens were inspected for any signs of fractures and cracks to categorize failure patterns. Thereby, the values of fracture strength showed that there were statistically nonsignificant differences between the tested groups (p &lt; 0.05). However, a significant difference (p = 0.01) was found between group 1 (inlays) (1950 ± 405) and group 6 (onlays) (3900 ± 770). Type III or type IV fracture modes were seen in the majority of the specimens. In conclusion, inlays and onlays made of zirconia using CAD/CAM technology were deemed reliable for restoring premolars, irrespective of the cavity-preparation design, except for inlays with a 75% intercuspal distance.

Effects of removing superficial layer of cartilage on the surface morphology and mechanical behavior of cartilage

Superficial cartilage defect is an important factor that causes osteoarthritis. Therefore, it is very important to investigate the influence of superficial cartilage defects on its surface morphology and mechanical properties. In this study, the knee joint cartilage samples of adult pig were prepared, which were treated by enzymolysis with chymotrypsin and physical removal with electric friction pen, respectively. Normal cartilage and surface treated cartilage were divided into five groups: control group (normal cartilage group), chymotrypsin immersion group, chymotrypsin wiping group, removal 10% group with electric friction pen, and removal 20% group with electric friction pen. The surface morphology and structure of five groups of samples were characterized by laser spectrum confocal microscopy and environmental field scanning electron microscopy, and the mechanical properties of each group of samples were evaluated by tensile tests. The results show that the surface arithmetic mean height and fracture strength of the control group were the smallest, and the fracture strain was the largest. The surface arithmetic mean height and fracture strength of the removal 20% group with electric friction pen were the largest, and the fracture strain was the smallest. The surface arithmetic mean height, fracture strength and fracture strain values of the other three groups were all between the above two groups, but the surface arithmetic mean height and fracture strength of the removal 10% group with electric friction pen, the chymotrypsin wiping group and the chymotrypsin soaking group decreased successively, and the fracture strain increased successively. In addition, we carried out a study on the elastic modulus of different groups, and the results showed that the elastic modulus of the control group was the smallest, and the elastic modulus of the removal 20% group with electric friction pen was the largest. The above study revealed that the defect of the superficial area of cartilage changed its surface morphology and structure, and reduced its mechanical properties. The research results are of great significance for the prevention and repair of cartilage injury.

The Influence of Ferrule Design and Pulpal Extensions on the Accuracy of Fit and the Fracture Resistance of Zirconia-Reinforced Lithium Silicate Endocrowns.

The study aimed to assess the marginal, axial, and internal adaptation, as well as the fracture resistance of zirconia-reinforced lithium silicate (ZLS) endocrowns with varying pulpal inlay extensions and marginal geometry. Sixty extracted maxillary first molar teeth were divided into six groups (n = 10) according to pulpal inlay extension and marginal configuration. The first three groups (J2, J3, and J4) utilized prepared teeth for endocrowns without ferrule design and 2 mm, 3 mm, and 4 mm pulpal extensions, respectively. The second three groups (F2, F3, and F4) utilized prepared teeth with 1 mm shoulder margins and 2 mm, 3 mm, and 4 mm pulpal extensions. The endocrowns were fabricated from ZLS blocks using CAD/CAM milling technology. After cementation, the specimens underwent thermal aging for 5000 cycles and were evaluated for marginal adaptation. Using a universal testing machine, the fracture resistance was tested under quasistatic loading (1 mm/min). Two-way ANOVA and the Tukey's post hoc test were employed for data analysis (p ≤ 0.05). The results of this study revealed that endocrowns without ferrule exhibited superior fracture strength than a 1 mm ferrule design p < 0.05, irrespective of the inlay depth. All designs with and without ferrule and all inlay depths showed clinically acceptable marginal and internal fit. The conventional endocrown design without ferrule and 2 mm inlay depth showed the lowest surface gap. The pulpal surface showed the highest discrepancy among all groups compared to the other surfaces. Endocrowns without ferrule are more conservative and have higher fracture strength than 1 mm ferrule designs; extending the inlay depth showed a significant increase in fracture resistance of the 1 mm ferrule design, but not for the conventional design without ferrule and 2 mm inlay depth. All groups exhibited a high auspicious fracture strength value for molar endocrown restorations.

Development and characterization of nano-magnesia-based refractories filled with graphite nanosheets

Thermo-mechanical and mechanical properties of Magnesia-Carbon (MgO–C) refractories are of great importance in industrial furnace applications and are greatly influenced by the amount of carbon in the MgO Matrix. In this research work, the effect of exfoliated graphite nanosheets (EGS) content on mechanical behavior and thermal shock resistance of MgO-based refractories was examined. MgO nanoparticles were synthesized by the co-precipitation method and micro-MgO particles were used as received. EGS was added in both micro and nano-MgO in variable amounts ranging from 0.5 to 2.5 wt % to study its effect on fracture strength and thermal shock resistance. The morphology of synthesized MgO nanoparticles and the fractured surfaces of the resultant composites were analyzed by field emission scanning electron microscopy (FESEM) coupled with energy dispersive x-ray (EDX) spectroscopy, transmission electron microscopy (TEM), X-ray diffraction analysis (XRD), and compression testing. The synthesized nano-MgO and as received micro-MgO particles were found to be of spherical morphology with no impurity elements as observed by FESEM and EDX mapping. XRD analysis did not show any phase change after the sintering of the composites. The FESEM and TEM images of the fractured surfaces of MgO-EGS refractory samples displayed the fine distribution of EGS. EGS were embedded in MgO particles, enhancing the composite-refractory samples' fractured strength. Fracture strength and thermal shock resistance were increased with the increasing amount of EGS in MgO. However, the highest fracture strength and thermal shock resistance values were achieved for nano-MgO with 2.5 wt% EGS. The resulting refractory samples can be used as furnace linings having a lower carbon content and enhanced thermo-mechanical properties.

Fracture strength of cad-cam milled polyetheretherketone (PEEK) post-cores vs conventional post-cores; an in vitro study.

The aim of this study was to compare the fracture strength and fracture modes of post-cores produced with CAD-CAM from modified polyetheretherketone (PEEK) materials with other custom-produced post-cores. Sixty human mandibular first premolars with equal root sizes were used. The teeth were divided into six groups (n = 10), and root canal treatment was performed. The teeth were separated from the roots over 2 mm from the cemento-enamel junction. As a result of the decoronation process, a 1 mm wide shoulder line was obtained for all teeth. For the fracture strength test, 10 mm deep post spaces were created on the teeth with a 1.6 mm diameter driller. Post-core groups consisted: everStick®glass fiber post-core (Group GF), zirconia post-core (Group Z), metal (Cr-Co) post-core (Group M), PEEK post-core without filler (Group UP), PEEK post-core with 20% TiO2 Filler (Group TP), and post-core with 20% ceramic filler (Group CP). Following the application of posts to post spaces, copings were created and cemented on the samples. With the universal tester, a force was applied to the long axis of the tooth with a slope of 135°. The mean fracture strength (N) between the groups was statistically evaluated using one-way ANOVA, and pairwise mean differences were detected using post hoc Tukey's HSD test among the groups. According to the results of the statistical analysis, a significant difference was found between the groups in terms of mean fracture resistance (p <0.05). Group Z (409.34±45.72) was significantly higher than Group UP (286.64±37.79), CP (298.00±72.30), and TP (280.08±67.83). Group M (376.17±73.28) was significantly higher than Group UP (286.64±37.79) and Group TP (280.08±67.83). There were no statistically significant differences between the means of the other groups (p >0.05). Among all the groups, Group Z exhibited a higher prevalence of repairable failure modes, while the rest of the groups predominantly experienced irreparable failure modes. In our study, zirconia and metal post-core samples showed higher average fracture strength values than PEEK post-cores groups. Repairable failure modes were more common in the zirconia post-cores, whereas the opposite was observed in the other groups. Further experimental and clinical trial studies are needed before PEEK materials can be used as post materials in the clinic.

Investigation of the Fracture Strength Between Dental Implant And Ti-Base Abutment Produced with Different Heights and Grades of Titanium Material

New prosthetic designs were developed to provide a balanced transmission of the stress caused by the chewing function to other mechanical and anatomical structures, and these designs revealed new research areas. An example of this is screw-retained implant-supported prostheses. With screw-retained prostheses, the residual cement problem is eliminated. However, abutment material and abutment design may adversely affect the mechanical and aesthetic properties of prostheses. Ti-base abutments have been developed to solve these problems. However, studies on clinical succes, material content and abutment height of ti-base abutments remain up-to-date. In our study, the effect or abutment heights on the bond strength and stress distribution with monolithic zirconia crowns in ti-base abutments manufactured from different titanium Gr types will be tested. Titanium Gr 4, Gr 5 and Gr 23 ELI materials will be used in our study. A total of 7 groups are planned with ti-base abutments with a abutment length of 3.5 mm, 5.5 mm for Gr 4 and Gr 5, abutment length of 3.5 mm, 5.5 mm and 7 mm for Gr 23. In the in vitro experiment, the fracture strength of the samples will be tested with the universal testing device. total of 77 implants, ti-base abutments and monolithic zirconia crowns will be used by creating 11 samples for each study group. The obtained values will be recorded in Newtons and Megapascals. The data will be analysed using the SPSS 22.0 programme. As a result, while the lowest fracture strength values were observed in Gr 4 Ti material in all ti-base abutment lengths in the samples for which the fracture strength test was performed, similar values were observed in the ti-base abutments produced from Gr 5 and Gr 23 ELİ alloys. When the relationship of bonding strengths with Ti alloys was evaluated, it was seen that there was no significant difference between Ti alloys.

The uniform and robust 8-inch CVD diamond plate generated by dual-magnetic field controlled DC Jet CVD

Diamond is a highly attractive material for many applications in material science, engineering, chemistry, and biology because of its favorable properties. The preparation of large-area freestanding diamond plate can greatly reduce the production cost of diamond and promote the industrialization of diamond. In this study, the dual-magnetic field mode was introduced to optimize the magnetic field distribution in direct current arc plasma jet chemical vapor deposition (DC Jet CVD) system, and the arc plasma was effectively controlled under the coupling of electric field and magnetic field. The uniformity of the plasma distribution above the substrate surface is significantly improved, resulting in long-term stable and uniform growth of the 8-inch freestanding diamond plate. The influence of dual-magnetic field mode on magnetic field generation, arc feature, and reactive group distribution was studied. 8-inch freestanding diamond plates with an average thickness of 2.8 mm were prepared by dual-magnetic controlled DC Jet CVD. The results showed that the 8-inch diamond plate preferred a high (220) orientation, and the deviation of thickness of which was around 10 % of the averaged values. Raman spectroscopy of diamond revealed a 6.6 cm−1 of full width at half maximum (FWHM) and calculated 1.20 GPa compressive stress in the 8-inch diamond plate. By means of mechanical and thermal property measurements, the large area diamond plate shows a robust structure with the average values of three-point bending fracture strength of 987.2 MPa, and extremely high thermal conductivity of 1797.8 W/(m·k) as well. The deviation of three-point bending fracture strength and the thermal conductivity over the 8-inch diamond plate was around 7.9 % and 12.6 % of the respective averaged values.

Effect of polyethylene fiber orientation on fracture resistance of endodontically treated premolars

Polyethylene fibers have been reported to improve the fracture resistance of endodontically treated teeth, but their optimal orientation is unclear. The purpose of this in vitro study was to evaluate the effects of different fiber positions and orientations on the fracture resistance of endodontically treated premolar teeth. One hundred endodontically treated maxillary premolars were divided into 2 groups according to the cavity design, mesio-occluso-distal and occluso-buccal, and each group was divided into 5 subgroups (n=10) according to the polyethylene fiber orientation on the pulpal floor: unidirectional horizontal (from mesial to distal), unidirectional vertical (from buccal to palatal), bidirectional (buccopalatal and mesiodistal), circular (around the walls), and without fibers (control group). The cavities were restored with fiber-reinforced composite resin and conventional composite resin. All the teeth were fractured with a universal testing machine and analyzed as catastrophic failure or reparable failure. A 1-way ANOVA was used to compare fracture strength values (α=.05). The tested groups with different fiber orientations showed significantly higher fracture load than the control group (P<.05). No statistically significant difference was observed among the fiber orientations (P>.05). Most of the favorable fractures were occlusal to the cemento-enamel junction, and adhesive failure were seen in the mesio-occluso-distal and occluso-buccal cavities. The highest percentage of unfavorable fractures and mixed failures was observed in the control group. The fiber orientation pattern in the mesio-occluso-distal and occluso-buccal cavities did not differ significantly in the fracture resistance of endodontically treated maxillary premolar teeth.

The Use of Fiber-Reinforced Composites for Restoration of Endodontically Treated Teeth: A Review

This review summarized the most recently published literature pertaining to the use of fiber-reinforced composite (FRC) to restore endodontically treated teeth (ETT) and its influence on the mechanical behavior of restored teeth. In-depth¬ literature review in Google Scholar, ScienceDirect and PubMed was performed for these keywords: “fiber-reinforced composite”; “fiber post”; “endodontically treated”; “short fiber-reinforced composite”— only published full-text articles between 2009 and 2021 are included in this review. Fourteen articles were selected for this review. The studies concentrated on laboratory-based research conducted on human and bovine extracted teeth with different restorative techniques. Fatigue survival and load to failure tests with assessment of survival rate and fracture strength values respectively, as well as fracture pattern analysis were done. We concluded that FRC materials have improved fracture strength of restored teeth compared to conventional composites using different restorative techniques, however not to the attained level of an intact natural tooth. In addition, authors recommend a better simulation of oral environment, such as dynamic fatigue-testing.

Ice Adhesion Characterization Using Mode-I and Mode-II Fracture Configurations

Abstract The ice buildup on airborne structures operating in cold weather conditions has detrimental impacts on their safety and performance. Due to practical applications, there has been a significant interest in ice removal strategies. However, the current body of literature lacks comprehensive insights into the mechanistic aspects of the ice adhesion/breakage process, resulting in a wide range of reported adhesion strengths that differ by two orders of magnitude. To address this gap, we employed a fracture mechanics-based approach to investigate the fracture behavior of a typical ice/aluminum interface in terms of mode-I and mode-II fractures. We examine a range of surface roughness values spanning from 0.05 to 5 micrometers. An experimental framework employing a single cantilever beam and direct shear tests were developed. The near mode-I and mode-II interfacial fracture toughness and strength values were extracted from the experimentally measured force and displacement by both analytical and numerical models employing cohesive surfaces. The combined experimental and numerical results show that ice adhesion is primarily driven by cohesive interfacial failure, which exhibits almost mode-independent fracture behavior. Mode-I fracture shows directional instability of crack propagation, which is attributed to thermally induced residual tensile stress at the ice layer-substrate interface. The fractographic inspection reveals similar ice-grain size over the examined range of substrate roughness values. For the examined range of surface roughness and temperature, which induces the Wenzel state with full surface wetting at the interface, the ice adhesion is insensitive to the interfacial roughness in both mode-I and mode-II fracture.

Pengaruh Penambahan Serat Kain Bekas Terhadap Sifat Mekanik Lis Gipsum

Research has been done on gypsum plaster. The purpose of this study was to see the mechanical properties of the addition of the percentage of used fabric fibers. Variations in the composition of gypsum flour and used cloth fiber were respectively: 2%, 4%, 6% and 8% with a water cement factor (FAS) of 0.5. Making samples of gypsum plaster using a hot press machine using a temperature of 90 °C within 30 minutes. The mechanical properties tested include fracture strength and flexural strength. The test equipment used for MOR and MOE is UTM. The test results show that the gypsum plaster with used fabric fibers has a fracture strength value of 953.1 kgf/cm2 to 2,981.4 kgf/cm2 and a flexural strength value of 63,519.67 kgf/cm2 up to 408,454.61 kgf/cm2. all samples of gypsum plaster have complied with SNI 01-4449-2006 concerning fiberboard quality standards.