Removing Fractured Endodontic Files with a Tube Technique-The Strength of the Glued Joint: Tube-Endodontic File Setup

One recommended technique for removing broken root canal instruments is to glue the fragment into a cannula adapted to it (i.e., the tube technique). The aim of the study was to determine the influence of the adhesive kind and length of the joint on the breaking force. During the investigation, 120 files (60 H-files and 60 K-files) and 120 injection needles were used. Fragments of broken files were glued into the cannula using one of three materials: cyanoacrylate adhesive, composite prosthetic cement, or glass ionomer cement. The lengths of the glued joints were 2 and 4 mm. After the polymerization of adhesives, a tensile test was carried out to find a breaking force. The results were statistically analyzed (p < 0.05). For 4 mm lengths of glued joints, the breaking force was higher than for 2 mm for both file types (K and H). In the case of K-type files, the breaking force was higher for cyanoacrylate and composite adhesives than glass ionomer cement. For H-type files, no significant difference in joint strength was found between binders at 4 mm, while at 2 mm, a much better connection was obtained for cyanoacrylate glue than prosthetic cements.

Impact of Physical and Chemical Modification of the Surface of Porous Al2O3 Ceramic Membranes on the Quality of Transferred HSMG® and CVD Graphene

Graphene transfer onto ceramics, like Si/SiO₂, is well-developed and described in the literature. However, it is problematic for other ceramic materials (e.g., Al₂O₃ and ZrO₂), especially porous ones. In this case, it is mainly due to poor adhesion to the substrate, resulting in strong degradation of the graphene. For these reasons, the research topic of this study was undertaken. This article presents research on the development of the methodology of graphene transfer onto ceramic Al₂O₃ surfaces. Polycrystalline graphene chemical vapour deposition (CVD) monolayer and quasimonocrystalline high-strength metallurgical graphene (HSMG^®) synthesised on liquid copper were used. When developing the transfer methodology, the focus was on solving the problem of graphene adhesion to the surface of this type of ceramic, and thus reducing the degree of graphene deterioration at the stage of producing a ceramic-graphene composite, which stands in the way of its practical use. Plasma and chemical ceramic surface modification were applied to change its hydrophobicity, and thus to improve the adhesion between the graphene and ceramic. The modification included the use of dielectric barrier discharge (DBD) plasma, oxygen plasma (RF PACVD method - Radio Frequency Plasma Assisted Chemical Vapour Deposition), and hydrofluoric acid treatment. Changes in surface properties caused by the modifications were determined by measuring the contact angle and (in the case of chemical modification) measuring the degree of surface development. The effectiveness of the applied surface preparation methodology was evaluated based on the damage degree of CVD and HSMG^® graphene layer transferred onto modified Al₂O₃ using optical microscopy and Raman spectroscopy. The best average I_D/I_G ratio for the transferred HSMG^® graphene was obtained after oxygen plasma modification (0.63 ± 0.18) and for CVD, graphene DBD plasma was the most appropriate method (0.17 ± 0.09). The total area of graphene defects after transfer to Al₂O₃ was the smallest for HSMG^® graphene after modification with O₂ plasma (0.251 mm²/cm²), and for CVD graphene after surface modification with DBD plasma (0.083 mm²/cm²).

Tribological Characteristics of a-C:H:Si and a-C:H:SiOx Coatings Tested in Simulated Body Fluid and Protein Environment

This paper presents the tribological properties of silicon and oxygen incorporated diamond-like carbon coatings tested in simulated body fluid and bovine serum albumin environments. The tests were performed using a ball-on-disc tribometer with an AISI316L steel counterbody. The wear tracks and wear scars were analyzed using optical microscopy and a nanoindenter. The interaction between the coating and the working environment was analyzed by Fourier transform infrared spectroscopy, whereas changes in the chemical structure before and after the tribological tests were compared with the use of Raman spectroscopy. Our study showed that the tribological parameters are governed by the presence of oxygen rather than the changing concentration of silicon. Both of the spectroscopy results confirm this statement, indicating that coatings with low concentrations of silicon and oxygen appear to be better candidates for biological applications in terms of wear resistance.

Sodium Alginate/Gelatine Hydrogels for Direct Bioprinting-The Effect of Composition Selection and Applied Solvents on the Bioink Properties

Hydrogels tested and evaluated in this study were developed for the possibility of their use as the bioinks for 3D direct bioprinting. Procedures for preparation and sterilization of hydrogels and the speed of the bioprinting were developed. Sodium alginate gelatine hydrogels were characterized in terms of printability, mechanical, and biological properties (viability, proliferation ability, biocompatibility). A hydrogel with the best properties was selected to carry out direct bioprinting tests in order to determine the parameters of the bioink, adapted to print with use of the designed and constructed bioprinter and provide the best conditions for cell growth. The obtained results showed the ability to control mechanical properties, biological response, and degradation rate of hydrogels through the use of various solvents. The use of a dedicated culture medium as a solvent for the preparation of a bioink, containing the predicted cell line, increases the proliferation of these cells. Modification of the percentage of individual components of the hydrogel gives the possibility of a controlled degradation process, which, in the case of printing of temporary medical devices, is a very important parameter for the hydrogels' usage possibility-both in terms of tissue engineering and printing of tissue elements replacement, implants, and organs.

Biological properties of carbon powders synthesized using chemical vapour deposition and detonation methods

Carbon powders can be synthesized using variety of CVD and detonation methods. Several interesting properties of carbon powder particles make them a very attractive material examined in many laboratories all over the world. However there is a lack of information discussing investigation of carbon powders directed to its application in pharmaceutical-cosmetic industry and medicine. Earlier investigation results proved that diamond powders present properties fighting free radicals. Presented work discusses the influence of carbon powder particles manufactured using MW/RF PACVD, RF PACVD and detonation methods onto hydro-lipid skin coat. Before the biological examinations physicochemical properties of carbon powders were determined. Grain size, shape and chemical composition of carbon powders were determined using the scanning electron microscopy. Surface functional groups were characterized by IR Fourier-transform spectroscopy and X-ray photoelectron spectroscopy. Structure and phase composition were investigated by means of the Raman spectroscopy. Results of allergy tests performed on laboratory mice proved that carbon powder particles synthesized using different methods do not cause allergy. In the following stage, the group of 20 patients applied the formula including carbon powder on their face skin. The influence of carbon powder onto hydro-lipid skin coat was determined by measurement of such parameters as: pH reaction, skin temperature, lipid fotometry and level of hydration. Additionally, macro pictures of places where the cream had been applied were registered. As the result of the investigation it was found that powders synthesized using various methods present different physicochemical properties which may individually affect the face skin parameters. The noticeable improvement of hydro-lipid skin coat kilter was observed.

The cause of 2S Diapason screw breakage after internal lumbar fixation: studies of the mechanical and material properties of the implant

In the years 1994-99, unstable fractures of the lumbar spine were surgically treated with interbody fixation in the Department of Neurosurgery at the Nicholas Copernicus Voivodeship Specialized Hospital in Łódź, using stabilizers manufactured by various companies. Complications in the form of stabilizer breakage were observed in 1 case out of 22. The aim of the present study was to ascertain the reason why the Stryker 2S Diapason screws broke. Tests performed to measure the material and mechanical properties of the implant did not show any signs of material fatigue, nor were any material defects discovered. However, a scanning microscope investigation confirmed the hypothesis that the material had crumbled due to overload. This discovery led to the decision that screws would be mounted in the bodies of the vertebrae in a manner decreasing implant load.

The application of nanocrystaline diamond coatings in medicine

The search for an endoprosthesis with the longest possible durability has been in progress for many years. In spite of three decades of intensive development of implant materials, contemporary endoprosthesis are still far from satisfactory. In an environment as corrosive as the human body, even the best metal alloys release ions: Co, Cr and Mo all dissolve at a rate of approximately 50 ng per year. The biocompatibility of an implants is directly by the extent of corrosion. Tests in vivo have shown that Ni, Co and Cr ions are bound to the body's own proteins, predominantly albumins, which can then transfer them to other ergans, thus disturbing their functions.<br /> Facing this challenge, a new, entirely cementless endoprosthesis for the coxofemoral joint, comprised of a pin, a head and two bushings, has been constructed in a cooperative project involving three research centers: ECAM in Lyons, the Technical University of Bratislava, and the Thin Film Division of the Technical University of Lodz. Both the pin and the outer bushing are made of a titanium alloy, coated with a nanocrystalline diamond film. The heads is made of corundum ceramics, and the inner bushing is made if high molecular weight polyethylene. The shape of the pin has been designed in compliance with all biomechanical requirements.<br /> As of this writing these endoprostheses have been implanted in test animals, and remain under continous biological monitoring. To this point all the test results have been postitive.