română ȘTEFAN GEORGE CĂLINOIU, CORNELIA BÎCLEȘANU, ANAMARIA FLORESCU, CĂTĂLIN CONSTANTIN DUMITRU, MIHAI EFTIMIE, ANTON FICAI
Abstract
The aim of this study is to compare the mechanical strength in compression, tension and FTIR microscopy of 2 types of dental adhesives: 4th generation, considered the "gold standard" and the latest generation adhesives called universal adhesives.
In the dental community, I have noticed that opinions regarding the two adhesives are divided. More comfortable and younger doctors prefer universal adhesive because it gives them easier and faster working times. And the experienced doctors who used the 4th generation adhesive claim that after using the universal adhesive they returned to the "gold standard".
We compared the two adhesives regarding the adhesion they achieve through compressive forces and tensile forces. The compression was carried out with the help of a press and on blocks of Gradia Direct Posterior filling material, which after the first test, the blocks were reformed with the help of the 2 adhesives and retested. After the traction that was performed on extracted teeth on which fillings were made similar to clinical situations, the detachment area was studied under the FTIR microscope.
In tests, All-Bond 3® Bisco adhesive had higher bond strength and compressive strength than CLEARFIL™ Universal Bond Quick Kuraray. Following the tensile tests, the values obtained showed a higher adhesion to the 4th generation adhesive. Also, the interface area where debonding occurred showed that the 4th generation adhesive is superior in terms of adhesion to dental tissues.
Keywords
universal, 4th generation adhesives. compressive, tensile, adhesion
SEBASTIAN VÂLCEA, BOGDAN DUMITRIU, VALENTIN NIȚESCU, MIRCEA BEURAN, MIHAI ȘTEFAN
Abstract
Postoperative pancreatic fistula is the leading cause of morbidity and mortality in patients undergoing pancreatic resection. The pancreatic duct stenting technique during pancreatic anastomosis does not reduce the incidence of postoperative pancreatic fistula after cephalic pancreatoduodenectomy. The drainage method includes the use of an external or internal stent . The current literature suggests that the use of an internal pancreatic duct stent does not help to reduce the leakage rate of pancreatic anastomosis after pancreatic resection, and it may increase the risk of pancreatic fistulas in soft pancreases [1].
We report here the case of a 74-year-old patient, who 15 years ago underwent a Whipple-type cephalic duodenopancreatectomy, the operative indication being a Vaterian ampulla, for which the anastomosis prosthesis was performed with a plastic stent placed intraoperatively at the level of the Wirsung canal later, in 2022, he developed a late pancreatic fistula through the migration of the transparietal stent to the skin level.
Pancreatic postoperative fistula represents a major cause of morbidity and mortality in pancreatic surgery. Therefore, many surgical techniques have been undertaken and tested to prevent the occurrence of pancreatic fistula and its related complications, also useful for decreasing mortality rates among these patients.
Keywords
stent, fistula, pancreas, morbidity
BENOUIS ALI, AIT KACI DJAFAR,ZAHI RACHID, MOULGADA ABDELMADJIDÉ, ZAGANE MOHAMMED EL SALLAH,MOHAMMED BENTAHAR, BOUTABOUT BENALI
Abstract
This study represents an in-depth exploration of stress distribution within polymethylmethacrylate (PMMA) orthopedic cement, a critical material used in hip prostheses. Focusing on the inherent fragility of the cement and its intricate interface with implants, our research meticulously investigates stress patterns surrounding individual cavities. What sets this study apart is its nuanced examination of interactions between multiple cavities and their consequential effects on both stress intensity and distribution. The findings from this research offer nuanced and illuminating insights into the interconnected nature of cavities, aligning closely with observations derived from real-world experiments. This study significantly advances our understanding of potential damage phenomena within total hip prostheses. Moreover, it establishes a robust foundation for potential advancements in the design and performance of prostheses, taking into account the complex interplay within orthopedic cement. These insights pave the way for more targeted improvements in the mechanical behavior of hip prostheses, thereby contributing to the ongoing evolution of orthopedic implant technology.
Keywords
Cement, implant, stress, bone, defect, rupture
MARISELVAM.P, VELMURUGAN.T, G.KARTHIKEYAN
Abstract
This paper focuses on the thermal properties of R-Glass/Epoxy laminate in response to temperature variations. The elastic properties and coefficient of thermal expansion in the material s principal direction were measured across the temperature range from room temperature to the cure temperature. These properties were then characterized as functions of temperature. Using the characterized properties and the principles of classical lamination theory, a method was proposed to predict the changes in the coefficient of thermal expansion for a general laminate subjected to temperature variations. The measured values of the coefficient of thermal expansion for laminates with varying angle plies were compared with the predicted values. The experimental results demonstrate that the proposed method accurately predicts the changes in the coefficient of thermal expansion for a general laminate under temperature variations. Additionally, an analytical formulation was proposed and validated to predict the changes in the coefficient of thermal expansion for R-Glass/Epoxy laminates subjected to temperature variations.
Keywords
R-Glass/Epoxy laminate, Thermal properties, Analytical model, Thermal expansion, Experimental
BRUNA MOREIRA, CARLOS JESUS, RAPHAELE MALHEIRO, AIRES CAMÕES
Abstract
Promoting the circular economy is one of the main tools to achieve carbon neutrality by 2050. The culture of using residues in cementitious materials, mainly in concrete, is already established, favouring circularity. Fly ash is commonly used in blended cement or concrete production as supplementary cementing material. However, waste glass is not as commonly used as a cement substitute. In this context, this research contributes to the knowledge about the use of waste glass as partial cement replacement, developing an experimental work. Glass bottles were transformed into glass powder using two different grinding processes. They were produced glass powders with different colours and fineness. These powders were used to produce mortars with 25% of glass powder replacing cement. Mortars containing fly ash were also produced. Their compressive strengths were evaluated over time. Results concluded that white, green, and brown glass powders are acceptable to be used as cement replacements. The results also identify glass powder as a potential substitute for fly ash.
Keywords
Glass powder; Fly ash; Cementitious materials; Circular economy; Low CO2
LEONID DVORKIN, VADIM ZHITKOVSKY, YURI RIBAKOV
Abstract
Reactive powder concrete (RPC) is an efficient type of fine-grained concrete with extreme strength and durability characteristics. The use of RPC allows the construction of such unique objects as pedestrian and automobile bridges, thin-walled architectural forms, protective structures, hazardous waste storage facilities, etc. Obtaining RPC provides for the mandatory use of a significant amount of microsilica as an active mineral additive, which is not always available for use. The article presents the results of comparing the strength characteristics of RPC obtained on microsilica and with its complete replacement with fly ash activated by milling with sodium silicate fluoride. The studies were carried out using mathematical planning of the experiment. Experimental-statistical models of RPC water demand and compressive and flexural strength at different ages have been obtained and analyzed. It is shown that the use of activated ash in the RPC makes it possible to obtain concrete with a strength of 100...110 MPa in 28 days. A method for calculating the composition of the RPC using the obtained models is proposed.
Keywords
reactive powder concrete, fly ash, microsilica, planning of experiments, experimental-statistical model, strength, concrete mix composition, design
İSMAİL HOCAOĞLU
Abstract
New construction materials have begun to be produced by using nano-technology. Nano aluminum oxide (nano-Al2O3) is known to have high electrical conductivity. In addition, nano-Al2O3 can increase the material s physical features and mechanical strength by spreading perfectly into cementitious composites like other nanomaterials. In this study, direct current (20V-DC) and alternating current (20V-AC) were applied to the nano-Al2O3-added to 300 dosage mortars (when they were fresh situation) for one day. It also investigated the mechanical-physical properties and microstructure of the mortars when nano-Al2O3 (0%, 1%, 1.5%, and 2% by weight instead of cement) was added. To determine the changes in the mortar s internal temperatures depending on DC and AC, the hydration temperatures of the mortars were measured every 60 seconds. It was observed that the optimum nano-Al2O3 ratio was 1%. It was also concluded that AC application was more effective in increasing the hydration temperature of the mortar. In terms of mechanical strength, It was seen that when DC-applied mortars were cured for 7 days and AC-applied mortars were cured for 28 days, they took higher values. Another result obtained from the study is that alternating cure improves the microstructure better than the direct current in cement-based materials.
Keywords
Nano aluminum oxide; Alternating current; Direct current; Internal temperature; Microstructure
PAVEL TOPALĂ, ALEXANDR OJEGOV, VITALIE BEȘLIU, DANIELA RĂILEANU
Abstract
Micro- and nano-technology is nowadays a field of production that grows up vigorously and attempts to solve the material and energy crisis that has affected all mankind on the one hand, and, on the other hand, it comes with new solutions in miniaturization of the technique and solving the problems faced by the compatibility of existing materials with the living matter, i.e. it comes with apply for a better life. The recent studies regarding the interaction of surface materials with plasma pulsed electrical discharges caused by a solitary discharge have shown that under the action of PEDM the active surfaces of the parts applied in machine building, electronics, chemical industry, food industry, medicine, etc. micro-modifications of these surfaces can take place, along with the formation of 3D-structured carbon films with micrometric thicknesses, synthesis of amorphous films of oxides and hydroxides of nanometres thicknesses. The application of surface micro-geometry modifications ensures the increase of the thermoelectric current of the electrons up to 10 times, the surface-active resistance by 107 times, the resistance to corrosion in the aggressive media from 2 to 100 times.
Keywords
micro-, nanotechnologies, pellicle, film, corrosion, emission, resistance