Testing Machine Research Articles

Preparation and Characterization of Tensile Properties of PMMA/SiC Nanowhiskers Nanocomposite Films: Effect of Filler Loading and Silane Treatment

The preparation of nanocomposites through melt mixing was challenging as the nanofillers tend to form agglomeration. The silicon carbide nanowhiskers (SiCNWs) filled poly (methyl methacrylate) (PMMA) thin film in this study was prepared by means of solution casting. Acetone with low toxicity was used as solvent to dissolve the PMMA pellets. A coupling agent, silane was used to enhance the properties of composite films. Besides, the untreated and treated SiCNWs were filled into PMMA matrix, respectively with the filler loading varied from 0.2 to 0.8 wt%. The universal testing machine was used to investigate the tensile properties of composites. It was found out that the tensile strength of the PMMA was reduced in the presence of SiCNWs. However, the tensile strength had increased with the rise of filler loading. At 0.8 wt% of SiCNWs, the composites’ tensile strength was comparable to virgin PMMA. Meanwhile, the SiCNWs had reduced the elongation at break but increased the elastic modulus of PMMA/SiCNWs nanocomposite films. In addition, silane surface treatment on SiCNWs had improved the tensile strength and ductility but lowered the elastic modulus of the nanocomposites. The improvement was due to the enhancement of interfacial adhesion between SiCNWs and PMMA.

Transverse compressive behavior of plain and polypropylene fiber-reinforced concrete infilled steel tubes as hybrid steel-concrete nodes for discrete reticulated shell structures

This study investigates using concrete infilled steel tubes as hybrid nodes for discrete reticulated shell structures under compressive loading transverse to the tube axis. Three configurations were tested: empty, plain concrete infilled and polypropylene fiber-reinforced concrete infilled steel tubes. Displacement-controlled loading was applied through welded steel plates. Simplified beam theory models and nonlinear finite element analysis were used to evaluate the structural behavior. The concrete infilled steel tube specimens had higher stiffness and load-bearing capacity than the empty ones. The structural behavior of the concrete infilled specimens could be split into pre- and post-split-tensile cracking phases. No significant difference was found between the plain and fiber-reinforced concrete specimens under loads up to 1500 kN, which was the load limit of the testing machine. An additional fiber-reinforced concrete specimen, tested on a higher capacity machine, had a load-bearing capacity of 2400 kN and exhibited ductile failure.

Ultrasonic A-Scan Signals Data Augmentation Using Electromechanical System Modelling to Enhance Cataract Classification Methods

The use of artificial intelligence in diverse diagnosis areas has significantly increased in the past few years because of the advantages it represents in clinical routine. Among the diverse diagnostic techniques, the use of ultrasounds is often preferred because of their simplicity, low cost, non-invasiveness, and non-ionizing characteristic. However, obtaining an adequate number of patients and data for training and testing machine learning models is challenging. To overcome this limitation, a novel approach is proposed for simulating data produced by ultrasonic diagnostic devices. The implemented method was based on a clinical prototype for eye cataract diagnosis, although the method can be extended to other applications as well. The proposed model encompasses the electric-to-acoustic signal conversion in the ultrasonic transducer, the wave propagation through the biological medium, and the subsequent acoustic-to-electric signal conversion in the transducer. Electrical modelling of the transducer was performed using a two-port network approach, while the acoustic wave propagation was modelled by using the k-Wave MATLAB toolbox. It was verified that the holistic modelling approach enabled the generation of synthetic data augmentation, presenting high similarity with real data.

Evaluation of some mechanical and optical properties of modified glass ionomer cement with TiO2 and SiO2 nanoparticles

BackgroundGlass ionomer cements with extended setting time and inferior mechanical properties present significant challenges for dentists in clinical practice. Thus, various alterations aimed to enhance their properties.Aim of the studyTo study the effect of adding TiO2 and SiO2 nanoparticles on properties of conventional glass ionomer cement.Methods2.5 wt% TiO2 and 2.5 wt% SiO2 were added to the glass ionomer cement (GC Gold Label Luting & Lining Cement, Japan). Microhardness, compressive strength, setting time and color changes were evaluated using Vickers hardness tester, Universal testing machine, Gillmore needle apparatus and spectrophotometer, respectively.ResultsData were analyzed using SPSS 18. Mean, SD, and confidence intervals were reported. Normality was checked using Kolmogorov–Smirnov test. The experimental group revealed a higher hardness value than the control group. Meanwhile, Compressive strength results revealed a higher value of the control group than experimental group. Setting time was longer for the experimental group, in the meantime no perceptible color change for the experimental group was recorded.ConclusionsAdding 2.5 wt% TiO2 and 2.5 wt% SiO2 to conventional glass ionomer had a positive effect on microhardness without affecting the perceptible color.

Lynch syndrome diagnostic testing pathways in endometrial cancers: a nationwide English registry-based study

BackgroundFor female patients with Lynch syndrome (LS), endometrial cancer (EC) is often their first cancer diagnosis. A testing pathway of somatic tumour testing triage followed by germline mismatch repair (MMR)...

Shear creep deformation of rock fracture distrubed by dynamic loading

The long-term stability of jointed rock masses is usually dominated by fault activation, which may be triggered by the dynamic disturbance generated by blasting during mining activities, leading to the occurrence of disasters such as landslides in open-pit and rockbursts in deep mining. The initial stress and dynamic disturbance are key factors that strongly affect the shear creep behavior of rock fractures. In this work, the shear failure instability of rock fractures of sandstone under creep-impact loading was experimentally investigated by using a creep-impact test machine, which allows for applying creep loading and an additional dynamic disturbance on rock fractures. Three stages of shear creep deformation, creep strain rate, and time-to-failure are examined under different creep stress levels and impact energies. Experimental results show that the tangential and normal creep rates increase with the increase of creep stress and impact energy, but the increment of tangential creep rate is higher than that of the normal creep rate. The time-to-failure of the creeping specimen is shortened under high creep stress and large impact energy, while the time-to-failure after the last dynamic disturbance of the specimen is determined by the total impact energy and creep stress level. By using high-speed photography, it is found that the failure types of rock depend on the magnitude of impact energy and creep stress level; that is, rock mainly slides with low stress levels and shears off with high stress levels. In addition, under different impact energy and creep stress levels, the variation of height is between 0.38 and 0.52, while the defined fracture factor, which describes the degree of failure of serrations, is between 0.30 and 0.54. The findings can provide deep insight into the fault sliding mechanism caused by mining activities, which provides theoretical support for the safe mining of ore in fault fracture zones.

Effects of radiotherapy dose and application time on the load-to-failure values of teeth filled with different sealers

BackgroundThe materials used in root canal filling and radiotherapy (RT) application can affect the load-to-failure of the teeth. This study aimed to compare the load-to-failure of the teeth filled with AH Plus (AHP) or AH Plus bioceramic (AHPB) before or after 60 Gy- and 70 Gy-dose radiotherapy.Materials and methodsOne hundred and ten maxillary incisors were endodontically prepared up to ProTaper Next X4 instruments. The teeth were randomly divided into 5 main groups as: non-irradiated, root canal treatment (RCT) before 60 Gy radiotherapy, RCT before 70 Gy radiotherapy, RCT after 60 Gy radiotherapy, RCT after 70 Gy radiotherapy. These groups were divided into 2 subgroups for filling material: AHP ve AHPB. After filling and radiotherapy procedures, the teeth were fixed on the thermoplastic mask plane. The plane were placed in the middle of a rectangular prism shaped glass phantom, and irradiated via a linear accelerator device. The teeth were then embedded in cylindrical acrylic blocks and the force (N) that caused the fracture was recorded under the Universal testing device. Student t-test was used for statistical comparisons. Statistical significance level was determined as p < 0.05.ResultsAfter 70 Gy dose radiotherapy, the group filled with AHPB showed statistically significantly lower fracture strength than the group filled with AHP (p < 0.05). In the control group, before 60 Gy RT group, after 60 Gy RT group, and before 70 Gy RT group, the sealers had statistically significantly similar load-to-failure. (p > 0.05).ConclusionThe group filled with AHPB caused a lower fracture strength than the group filled with AHP following a 70 Gy dose of RT. The sealers in the control group, before 60 Gy RT group, after 60 Gy RT group, and before 70 Gy RT group exhibited comparable load-to-failure values.

Flexural Strength of Different Commercially Available Auto-Polymerizing Acrylic Resins: An In Vitro Study.

Background Auto-polymerizing acrylic resins, composed primarily of poly(methyl methacrylate) and methyl methacrylate, are crucial in prosthetic dentistry due to their ease of use, cost-effectiveness, and acceptable aesthetics, polymerizing at room temperature to form solid polymer networks. One of the most important mechanical properties of these resins is flexural strength, which is essential for their performance under continuous masticatory forces. In clinical applications, prosthetic materials endure repetitive stress from chewing, and resins with higher flexural strength are better equipped to resist deformation and fractures. This property is vital for ensuring the long-term integrity of prostheses, minimizing the risk of material failure, and enhancing prosthetic longevity, thus contributing to better clinical outcomes and patient satisfaction. Objective Resins with superior flexural strength, such as DPI, provide better clinical outcomes. High flexural strength minimizes the risk of material failure in high-stress areas, especially in extensive restorations like temporary bridges or denture repairs. For clinicians, using materials with greater strength reduces the likelihood of restoration failure, ensuring more reliable performance and fewer interventions for repair or replacement. This study aims to evaluate and compare the flexural strength of three commercially available auto-polymerizing acrylic resins, Pyrax (Pyrax International, Uttarakhand, India), DPI (Dental Products of India, Mumbai, India), and Quick Ashvin (National Dental Supply Company, Delhi, India), to determine their suitability for various dental applications. Methodology Following American Dental Association specifications, 20 rectangular bar-shaped specimens (25 mm x 2 mm x 2 mm) of each resin type were prepared. The resins were mixed according to manufacturer instructions, poured into molds, and allowed to auto-polymerize at room temperature. Post-polymerization, specimens were immersed in artificial saliva at 37°C for 10 days to simulate oral conditions. Flexural strength was assessed using a three-point bending test on a universal testing machine, and results were analyzed using ANOVA and post-hoc Bonferroni tests. Results The flexural strength of DPI resin bars (mean=482.10 MPa, SD=17.28) was significantly higher compared to both Pyrax (mean=467.82 MPa, SD=15.01) and Quick Ashvin (mean=470.17 MPa, SD=8.18). ANOVA revealed a significant difference among the resins (F=5.956, p=0.004). Post-hoc Bonferroni comparisons showed a statistically highly significant difference between DPI and Pyrax (p=0.006) and a significant difference between DPI and Quick Ashvin (p=0.028). No significant difference was observed between Pyrax and Quick Ashvin (p=1.000). Conclusion DPI resin, with its superior flexural strength, is the best choice for high-stress dental applications, while Quick Ashvin offers balanced performance for interim uses such as temporary crowns. Pyrax, being more cost-effective, is suitable for less demanding cases. This study underscores the importance of selecting materials based on mechanical properties and calls for further research to enhance resin durability. For dental practitioners, DPI is ideal for long-lasting restorations, Quick Ashvin for temporary solutions, and Pyrax for budget-conscious cases.

Comparative Analysis of Shear Bond Strength in Orthodontic Brackets Between Milled and 3D-Printed Definitive CAD/CAM Restorations

Objective: The objective of this study was to evaluate the effect of different surface treatment methods on the shear bond strength (SBS) of metal brackets bonded to two types of CAD/CAM composite restorations: milled and 3D-printed. Materials and Methods: A total of 160 flat-shaped specimens (10 × 10 × 2 mm3) were prepared from four different CAD/CAM composites; two milled (Lava Ultimate™ [LU] and Grandio™ [GR]) and two 3D-printed (Crowntec™ [CT] and C&amp;B Permanent™ [CB]). These specimens underwent thermocycling (5000 cycles at 5–55 °C), then were categorized based on the surface treatment into four groups (n = 10): Group C (control, no surface treatment), Group HF (treated with 9.6% hydrofluoric acid), Group DB (mechanical roughening by a diamond bur), and Group SB (sandblasting using aluminum oxide). Metal brackets were bonded using Transbond XT Primer and universal adhesive, stored in artificial saliva for 24 h, then thermocycled again. Shear bond strength (SBS) was tested using a universal testing machine until bracket debonding occurred. The adhesive remnant index (ARI) was assessed using a stereomicroscope to quantify the residual adhesive following debonding. Result: Regarding material, GR and LU restorations had significantly higher SBS values compared to CT and CB, ranging from 13.90 MPa to 20.35 MPa. Regarding surface treatment, SB and HF groups showed significantly higher SBS values. The ARI scores showed different adhesive modes of failure, with higher instances of scores 0 and 1, which indicate no or minimal adhesive remaining. Conclusions: Both milled and 3D-printed materials had adequate SBS for clinical use, with milled materials showing superior results. Surface treatments like sandblasting and HF significantly improved bond strength, with adhesive failure being common.

3D-printed one-piece versus two-piece orthodontic clear aligner attachments bonded with provisional crowns: A proof of concept

ObjectivesThis study aimed to introduce a novel technique for fabricating provisional crowns integrated as a single unit with aligner attachments. MethodsA total of 60 crowns with attachments were prepared: 20 conventional (Protemp) and 40 3D-printed (20 bonded with attachments; 20 integrated with composite attachments as a single unit) using NextDent resin. Two central incisors were scanned (once without attachments and once with attachments) to create STL files for specimen printing. Half of the specimens (30, n = 10 per group) underwent thermal cycling (5000 cycles). Shear bond strengths (MPa) were evaluated using a universal testing machine. The debonded areas and attachment failures were analyzed to determine the fracture type. Data analyses were performed using ANOVA and post hoc Tukey tests (α = 0.05). ResultsThe 3D-printed specimens showed higher strength values than the bonded attachments per group (P < 0.001). The 3D-printed crowns with attachments demonstrated the highest strength (12.39 ± 1.92 MPa). Thermal cycling significantly decreased the bond strength of the attachments (P < 0.001), except in the 3D-printed crowns with composite attachments as a single unit, which showed no significant change after thermal cycling (P = 0.643). In the bonded attachment groups, the adhesive type was the predominant failure mode, while in the 3D-printed groups, attachment fractures were the primary cause of failure. ConclusionThe 3D-printed provisional crowns with attachments have high strength and is clinically appropriate for orthodontic treatment when temporization of teeth is indicated. Clinical SignificanceThe developed technique for fabricating 3D-printed provisional restorations with orthodontics attachments as a single unit is a promising approach. The technique may be incorporated into the digital orthodontic treatment workflow when temporization is indicated.

Static and dynamic mechanical behavior of high-strength 22SiMn2TiB armor steel and welded structure

High-strength advanced steel and welded structure are key for service safety and life. Static and dynamic compressive mechanical behavior of high-strength 22SiMn2TiB armor steel and welded structure is investigated, which are carried out by using universal testing machine and split Hopkinson pressure bar. The studied materials are obtained from high-strength steel matrix, welded seam and mix of them with interface, respectively. The strain rate in experiments covers the range of 0.001/s to 6000/s. The mechanical data involve stress-strain relations and strain rate dependencies of mechanical properties. The cracking behavior as well as the corresponding microstructures are characterized at different length scales from millimeter to micron scale by optical microscope and scanning electron microscope. The results show that static (0.001/s) and dynamic (5000/s) yield strengths are 1600 MPa and 2400 MPa for high-strength steel matrix, 400 MPa and 1200 MPa for welded seam, 950 MPa and 1600 MPa for mix of them with interface, respectively. Under dynamic loading, shearing occurs and results in the fracture. Along the interface of steel matrix and welded seam, cracks are firstly initiated and propagated. The relations of mechanical properties and fracture features are analyzed, where strain rate effect is mentioned. This work will guide the design and application for engineering structure.

Recent highlights from the BELLE and BELLE II experiments

The BELLE experiment at the KEKB collider in Tsukuba operated as a B-factory until 2018, making significant contributions to flavor physics. Building on this legacy, the BELLE II experiment, an upgraded version, now operates at the SuperKEKB energy-asymmetric e+e− collider. BELLE II has collected 424fb−1 of data, including 365fb−1 at the ϒ(4S) resonance. A wide range of physics topics can be studies with this data. In this proceeding, we review our latest results, which include tests of lepton flavor universality, Cabibbo-Kobayashi-Maskawa physics, searches for rare B-meson decays, and spectroscopy studies. We also discuss contributions to the gμ−2 prediction.

Reuse of polyvinyl chloride residues—in powder and fiber forms—as potential components for green mortar pavers

Plastic wastes are considered a significant environmental pollution load because of their mostly non-biodegradable nature. Consequently, the need to lessen the environmental impact calls for employing eco-friendly strategies such as reusing materials in construction. The objective of this study is to analyze the mechanical behavior and environmental impacts of mortar elements, with a specific focus on pavers, by incorporating waste polyvinyl chloride (WPVC) as aggregate and partially replacing cement. Two distinct forms of this waste were considered in the investigation: (i) as it is generated in industrial processes, mainly in fiber form, WPVCf, and in the form of powder obtained by sieving the former, WPVCp. The ratio of conventional mortar materials replaced by WPVC and the final water-to-binder ratio changed based on waste type and mix workability. The experimental work involved preparing 84 pavers, each measuring 100 mm × 150 mm × 60 mm. For each type of paver, 12 samples were prepared, ensuring a minimum of 4 sets of test data for each curing period (7, 14, and 28 days). Flexural strength tests, conducted in accordance with the Colombian standard NTC 2017, utilized a standard flexural test machine with a 150 kN capacity. A specially designed steel tool applied a point load at the center of each paving block, maintaining a minimum distance of 10 millimeters from the edges. The findings demonstrated that pavers containing fiber plastic waste exhibited the requisite strength for paved walkways, even in the short term, when the weight ratio of WPVCf to sand (WPVCf/S) was 24 %. These results derive an eco-friendly solution for reusing PVC wastes currently deposited directly in landfills. Moreover, to analyze the environmental impacts of this solution, a Life Cycle Assessment (LCA) analysis was carried out in this research. The LCA results pointed out that dosing with a WPVCf/S ratio of 24 % emerges as the most ecologically responsible, manifesting substantial reductions across impact categories, such as a significant 23 % decrease in climate change, a 23 % reduction in Photochemical ozone formation, and a 22 % reduction in renewable energy consumption. This underscores the potential of WPVCf incorporation as a consequential step toward eco-friendly construction materials. Furthermore, this solution not only translates to diminished paving block costs by requiring less fine aggregate and cement but also contributes to reduced transportation expenses owing to the decreased weight of the pavers.

A quasi-in-situ EBSD study on abnormal grain growth in 2219 aluminum alloy friction stir welded joints during post-weld heat treatment

Abnormal grain growth occurs in the friction stir welds of 2219 aluminum alloy during the solution treatment. To further investigate abnormal grain growth, the quasi-in-situ electron backscatter diffraction (EBSD) experiment, including the EBSD testing and heating by thermal simulation testing machine, was proposed to observe the grain growth process in the weld. The results show that the abnormal grain growth behavior in the stir zone and the thermo-mechanically affected zone is different, and different microstructures at different positions in the weld promote the growth of abnormal grains. In the stir zone, the modified Humphreys’ model is used to analyze the abnormal grain growth behavior. The grains with an advantage size and low strain are more likely to grow abnormally. The non-uniform pinning caused by the dissolution of second-phase particles further promotes abnormal grain growth. In the thermo-mechanically affected zone, the abnormal grains are formed by unstrained equiaxed grains near the stir zone or recrystallized sub-grains. The growth of abnormal grains in the thermo-mechanically affected zone is a strain-induced grain boundary migration process. The research is helpful to understand the abnormal grain growth in friction-stir welds during post-weld heat treatment.

Sputum and tongue swab molecular testing for the in-home diagnosis of tuberculosis in unselected household contacts: a cost and cost-effectiveness analysis.

Delayed and missed diagnosis are a persistent barrier to tuberculosis control, partly driven by limitations associated with sputum collection and an unmet need for decentralized testing. Household contact investigation with point-of-care testing of non-invasive specimens like tongue swabs are hitherto undescribed and may be a cost-effective solution to enable community-based active case finding. In-home, molecular point-of-care testing was conducted using sputum and tongue specimens collected from all household contacts of confirmed tuberculosis cases. A health economic assessment was executed to estimate and compare the cost and cost-effectiveness of different in-home, point-of-care testing strategies. Incremental cost effectiveness ratios of strategies utilizing different combination testing algorithms using sputum and/or tongue swab specimens were compared. The total implementation cost of delivering the standard of care for a 2-year period was $84 962. Strategies integrating in-home point-of-care testing ranged between $87 844 - $93 969. The cost-per-test for in-home, POC testing of sputum was the highest at $20·08 per test. Two strategies, Point-of-Care Sputum Testing and Point-of-Care Combined Sputum and Individual Tongue Swab Testing were the most cost-effective with ICERs of $543·74 and $547·29 respectively, both below a $2,760 willingness-to-pay threshold. An in-home, point-of-care molecular testing strategy utilizing combination testing of tongue swabs and sputum specimens would incur an additional 10.6% program cost, compared to SOC, over a 2-year period. The increased sample yield from tongue swabs combined with immediate result notification following, in-home POC testing would increase the number of new TB cases detected and linked to care by more than 800%.

Effect of Immersion of Denture Base Thermoplastic Nylon in Alkaline Peroxide and 10% Castor Oil (Ricinus Communis Oil) on Color Stability and Flexural Strength

Discoloration and flexural strength of denture bases are important factors affecting the comfort and durability of denture users. This study aims to determine the effect of immersion of nylon thermoplastic denture base in alkaline peroxide solution and 10% castor oil (Ricinus Communis Oil) on color stability and flexural strength. This study used a laboratory experimental design with samples of cylindrical (20 x 2 mm) thermoplastic nylon resin for color stability test and rectangular (65 x 10 x 3 mm) for flexural strength test. There were two study groups: one control group and two treatment groups immersed in alkaline peroxide and 10% castor oil solution, with two time variables, 8 days and 12 days. The total number of samples was 60, with each group having 10 samples. The color stability test used a colorimeter, and the flexural strength test used a universal testing machine. The results showed that there was no effect of soaking the nylon thermoplastic denture base in alkaline peroxide on color stability, with a value of p = 0.412 for 8 days and p = 0.179 for 12 days. In addition, there was no effect of immersion in alkaline peroxide and 10% castor oil on flexural strength, with p value = 0.076 for 8 days and p = 0.917 for 12 days. The implication of this study is that immersion in alkaline peroxide and castor oil solution does not affect the color stability or flexural strength of nylon thermoplastic denture bases, making them safe for long-term use.

GARGLING WITH RED BELT LEAF BOILING (PIPER CROCATUM) ON SALIVA pH IN STUDENTS SMP NEGERI 4 PINELENG MINAHASA DISTRICT

Abnormalities in the mouth or dental and oral diseases that occur in a person are usually caused by several factors. The intra-oral and extra-oral environment greatly influences a person's dental and oral health. To maintain healthy teeth and mouth, it is necessary to control saliva, because saliva or saliva in the mouth plays an active role in supporting healthy teeth and mouth. If there is a decrease in saliva pH, it can cause rapid demineralization of tooth elements, while an increase in pH can result in bacterial colonization which deposits and increases the formation of tartar. One way to control the pH of saliva is to gargle with boiled red betel leaves, because they contain compounds that are antibacterial. This study aims to determine the effectiveness of gargling with boiled red betel leaves (piper crocatum) on saliva pH in students at SMP Negeri 4 Pineleng, Minahasa Regency. This research uses a quasi-experimental method with a one group pre and post-test design. This research was carried out by giving treatment to respondents and measuring the pH of saliva before and after gargling with boiled red betel leaves. The sample in this study was 72 students, using random sampling techniques. Data collection was obtained from the results of salivary pH measurements using universal pH test paper with criteria 0-14, the concentration of red betel leaves used in this study was 15%. The data obtained were analyzed using the Wilcoxon test. Based on the results of the Wilcoxon test, it was found that ? value=0.027 (0.027&lt;0.05), so it can be concluded that gargling with boiled red betel leaves is effective in changing saliva pH.

Integrating Universal Hepatitis C Screening Into Adolescent Well Visits Is a "Win-Win" Scenario: Rationale and Demonstration of Real-world Feasibility and Implementation.

Hepatitis C virus (HCV) testing is recommended for all adults 18 years and older to increase identification of those with infection and facilitate prompt referral for curative antiviral therapy. While critical to promote elimination, this strategy excludes a key demographic group who are clearly at risk of undetected HCV infection and who could benefit from early treatment: adolescents. In this paper, we review the available data on the burden of HCV and the close association with injection drug use, discuss the rationale of universal testing in adolescents and, finally, present data from a quality improvement project implementing HCV testing into routine adolescent health visits.

Evaluation of Reliability and Validity of Different Thicknesses of Occlusal Contact Registration Strips Vs Conventionally used Articulating Papers – An Invitro Study

Aim: To compare and evaluate the reliability and validity of different thicknesses of Occlusal Contact Registration Strips (OCRS) under simulated occlusal load.  Settings and Design: In-Vitro Comparative Study  Materials and Methods: Articulated epoxy resin dental models obtained from completely dentulous patients were interposed with occlusal contact registration strip of various thicknesses and subjected to constant axial compressive load using universal testing machine. The photographs of consistent registration marks were subjectively assessed using a computer software.  Statistical Analysis Used: Analysis of Variance (ANOVA) and post hoc mean multiple comparison using Dunnett T3 test.  Results: The thinnest occlusal registration strip used in this study registered the highest average number of markings with a borderline statistically significant difference (P=0.06). The highest average area of markings was registered by the thickest strip, which had a near marginal significance (P=0.09), whereas the lowest average area was produced by the thinnest strip which was statistically significant (P=0.03).  Conclusion: There exists a relationship between the thickness of an occlusal contact registration strip, the number and the area of the marks registered. The average number of marks registered was inversely proportional to the thickness of the occlusal indicator. Hence, the thinner the occlusal contact registration strip, the more reliable is the occlusal contact registration. The average area of occlusal contact registration mark varies proportionately to its thickness. Hence, the thickest occlusal contact registration strips were more valid for marking occlusal contacts.

Failure resistance of single-implant crowns assembled from polyetheretherketone and lithium disilicate abutments and different crown materials after artificial aging.

The objective of the present study was to investigate the effect of using different materials for the fabrication of implant abutments and crowns on the mechanical behavior of implant-supported single crowns after artificial aging. The materials were tested in different combinations to reveal whether using stiff or resilient materials as an abutment or a crown material might influence the fracture strength of the whole structure. A total of 40 implants (blueSKY) were restored with identical custom-made CAD/CAM abutments milled out of lithium disilicate or ceramic-reinforced polyetheretherketone (PEEK) and divided into five test groups (n &#61; 8). Forty crowns made of three different materials (zirconia, lithium disilicate, and ceramic-reinforced PEEK) were used to restore the abutments. Specimens were subjected to mechanical loading up to 1,200,000 cycles in a chewing simulator (Kausimulator) with additional thermal cycling. The surviving specimens were subjected to quasi-static loading using a universal testing machine (Z010). The PEEK abutments with zirconia crowns showed the highest median failure load (3890.5 N) while the PEEK abutments with lithium disilicate crowns exhibited the lowest (1920 N). Fracture and deformation occurred in both the crowns and abutments. The failure load of the restorations was influenced by the material of the abutment and crown. Restoring PEEK abutments with zirconia crowns showed a high failure load and no screw loosening.