Migration of titanium dioxide microparticles and nanoparticles through the body and deposition in the gingiva: an experimental study in rats

The aim of this experimental work was to evaluate deposition of titanium dioxide (TiO₂) microparticles and nanoparticles, which could originate from titanium bioimplants, in the gingiva. Wistar rats were injected intraperitoneally (i.p.) with a suspension of TiO₂ particles of different sizes (150, 10, or 5 nm). The rats were killed 12 months post‐injection, and the buccal and lingual gingivae were resected and evaluated using light and scanning electron microscopy. Energy‐dispersive X‐ray spectroscopy (EDS) was used to confirm the presence of titanium in deposits of microparticles and nanoparticles, and the concentration of titanium in tissues was measured using inductively coupled plasma–mass spectrometry (ICP‐MS). Histological examination showed that all experimental groups exhibited agglomerates, in the gingiva, of titanium particles of micrometer size range, with no associated inflammatory response. Higher concentrations of titanium traces were shown, by ICP‐MS, in both buccal and lingual tissues of all experimental groups compared with their matched controls. Titanium concentrations were significantly higher in the buccal gingiva than in the lingual gingiva, and after injection with 5‐nm particles than with 10‐nm particles in both localizations. Titanium microparticles and nanoparticles deposit in the gingiva, and mostly on the buccal side. Gingival deposition of titanium could be considered a tissue indicator of tribocorrosion processes of titanium bioimplants.     

Exercise handout and one-on-one hand therapy for management of stiffness after plaster cast immobilization of simple phalangeal and metacarpal fractures in children: A randomized,noninferiority trial

Study DesignThis is a noninferior, single-blind, randomized controlled trial.IntroductionJoint stiffness is common after plaster cast immobilization for simple phalanx and metacarpal fractures in children. The limited literature suggests this joint stiffness in children resolves without one-on-one therapy; however, without robust studies confirming that there is no detrimental effect from withdrawing treatment, many children are still referred.Purpose of the StudyThe purpose of this study was to determine if an educational handout for self-management of stiffness is noninferior to one-on-one hand therapy for achieving full range of motion (ROM).MethodsParticipants were randomly assigned to group one who received the handout or group two who received hand therapy in addition to the handout. The ROM was measured by composite flexion and total active motion (TAM). The noninferiority margin was 10% difference between the two groups in the proportion of participants who achieved full ROM at two weeks after cast removal.ResultsSixty participants in each group completed the study. Group difference for composite flexion was 1.7% (95% CI: −3.9% to 7.2%), demonstrating noninferiority. Group difference for TAM was inconclusive at 8.3% (95% CI: −2.1% to 18.7%). Sensitivity analysis adjusting for participants with full composite flexion at the baseline resulted in the group difference for composite flexion of 3.1% (95% CI: −3.6% to 9.8%), maintaining noninferiority, but group difference for TAM at 10.4% (95% CI: 0.0% to 20.9%), was inconclusive with the handout group significantly worse.ConclusionAn educational handout is noninferior to hand therapy for achieving full ROM in composite flexion but not TAM. This needs to be taken into consideration for changing clinical practise.     

Effect of Mucin and Bicarbonate Ion on Corrosion Behavior of AZ31 Magnesium Alloy for Airway Stents

The biodegradable ability of magnesium alloys is an attractive feature for tracheal stents since they can be absorbed by the body through gradual degradation after healing of the airway structure, which can reduce the risk of inflammation caused by long-term implantation and prevent the repetitive surgery for removal of existing stent. In this study, the effects of bicarbonate ion (HCO₃⁻) and mucin in Gamble’s solution on the corrosion behavior of AZ31 magnesium alloy were investigated, using immersion and electrochemical tests to systematically identify the biodegradation kinetics of magnesium alloy under in vitro environment, mimicking the epithelial mucus surfaces in a trachea for development of biodegradable airway stents. Analysis of corrosion products after immersion test was performed using scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX) and X-ray diffraction (XRD). Electrochemical impedance spectroscopy (EIS) was used to identify the effects of bicarbonate ions and mucin on the corrosion behavior of AZ31 magnesium alloys with the temporal change of corrosion resistance. The results show that the increase of the bicarbonate ions in Gamble’s solution accelerates the dissolution of AZ31 magnesium alloy, while the addition of mucin retards the corrosion. The experimental data in this work is intended to be used as foundational knowledge to predict the corrosion behavior of AZ31 magnesium alloy in the airway environment while providing degradation information for future in vivo studies.     

Characterisation of Crevice and Pit Solution Chemistries Using Capillary Electrophoresis with Contactless Conductivity Detector

The ability to predict structural degradation in-service is often limited by a lack of understanding of the evolving chemical species occurring within a range of different microenvironments associated with corrosion sites. Capillary electrophoresis (CE) is capable of analysing nanolitre solution volumes with widely disparate concentrations of ionic species, thereby producing accurate and reliable results for the analysis of the chemical compositions found within microenvironment corrosion solutions, such as those found at crevice and pit corrosion sites. In this study, CE with contactless conductivity detection (CCD) has been used to characterize pitting and crevice corrosion solution chemistries for the first time. By using the capillary electrophoresis with contactless conductivity detection (CE-CCD) system, direct and simultaneous detection of seven metal cations (Cu²⁺, Ni²⁺, Fe³⁺, Fe²⁺, Cr³⁺, Mn²⁺, and Al³⁺) and chloride anions was achieved with a buffer solution of 10 mM 2,6-pyridinedicarboxylic acid and 0.5 mM cetyltrimethylammonium hydroxide at pH 4 using a pre-column complexation method. The detection limits obtained for the metal cations and chloride anions were 100 and 10 ppb, respectively. The CE-CCD methodology has been demonstrated to be a versatile technique capable of speciation and quantifying the ionic species generated within artificial pit (a pencil electrode) and crevice corrosion geometries for carbon steels and nickel-aluminium bronze, thus allowing the evolution of the solution chemistry to be assessed with time and the identification of the key corrosion analyte targets for structural health monitoring.     

Annealing Effects in Twin-Roll Cast AA8006 Aluminium Sheets Processed by Accumulative Roll-Bonding

Ultrafine grained sheets were prepared from a twin-roll cast AA8006 aluminium alloy using accumulative roll-bonding process at room temperature. The evolution of microstructure of sheets after three accumulative roll-bonding passes during isochronal annealing with a constant step of 20 °C/20 min was studied by light and electron microscopy. The influence of the resulting microstructure on mechanical properties was monitored by microhardness measurements. The microhardness increases when the material is annealed up to 160 °C. Above this temperature a fast drop of microhardness occurs followed by a negligible variation at annealing temperatures exceeding 300 °C. In order to map continuously the microstructure changes during annealing, the in situ TEM experiments in the heating stage were performed as a supplement to post-mortem TEM observations.     

Effect of Benzotriazole on the Localized Corrosion of Copper Covered with Carbonaceous Residue

Carbonaceous residues on copper pipes during the manufacturing process are known to be one of the main causes of pitting corrosion on copper pipes. This study examined the corrosion-inhibiting effect of benzotriazole (BTA) on {"type":"entrez-nucleotide","attrs":{"text":"C12200","term_id":"1559753"}}C12200 copper pipes with carbonaceous film in synthetic tap water. In the absence of BTA, localized corrosion mechanisms due to galvanic corrosion, crevice corrosion, and oxygen-concentration cell were proposed in the boundary part of the carbonaceous film on the copper through X-ray photoelectron spectroscopy (XPS), scanning electron microscopy (SEM) with energy dispersive spectrometer (EDS) analyses. Electrochemical tests showed that BTA inhibits corrosion by forming Cu−BTA complexes on all over the copper surface where carbonaceous film is present. BTA mitigates galvanic corrosion and crevice corrosion at the boundary of the carbonaceous film and suppresses the formation of oxygen-concentration cells through the formation of a Cu−BTA complex.     

青少年和儿童牙冠与牙弓遗传度的研究

错畸形的病因学研究是口腔正畸学的热点之一。错畸形多具有遗传倾向,表现为亲代与子代之间牙及颅面性状的相似性,牙齿发育作为全身发育的一部分,环境因素可以通过影响基因的表型而使牙齿发育表现多种多样,但牙齿发育受遗传因素影响更大[1]。牙冠宽度是牙齿形态测量及牙量指数的重要指标,牙弓形状、大小与牙弓间隙分析、矫治后牙弓的稳定性密切相关。牙冠和牙弓的测量值在正畸诊断和治疗中具有重要意义。该文对遗传性因素影响牙齿和牙弓正常发育的研究现状进行概述,以期为错畸形的临床诊断和治疗提供参考。     

Analysis of the Abrasive-Type Influence on the Effectiveness of Rotary Cleaning of Machine Parts with Complex Geometric Features

This work presents the analysis of functional relationships between fraction size of abrasives and geometric parameters of surfaces after rotary cleaning. The influence of an abrasive type on the effectiveness of rotary cleaning of machine parts with complex geometric features was determined as well. The process of mechanical cleaning, using a rotational method, of clutch springs was performed in the proprietary device for rotational cleaning, which was followed by the computer-aided analysis of the obtained results. The research process was carried out using abrasive materials such as grinding stone, sand, basalt, glass, and fine gravel, and the test samples were clutch springs after eight years of operation. Based on calculated three-dimensional (3D) roughness values of the cleaned samples’ surfaces, qualitative classification of abrasives was determined. The most effective material turned out to be fine gravel, while the worst results were related to basalt usage.     

Characterization of W–Cr Metal Matrix Composite Coatings Reinforced with WC Particles Produced on Low-Carbon Steel Using Laser Processing of Precoat

The paper presents the study results of laser processing of precoat applied on C30 steel. The precoat consisted of powder mixtures with a binder in the form of water glass. Tungsten powder, chromium, and tungsten carbide (WC) were used to produce the precoat. The laser processing was carried out using a Yb:YAG disc laser with a rated power of 1 kW. Constant producing parameters (power of laser beam, 600 W; laser beam scanning rate, 400 mm/min) were applied. Chemical composition of the precoat was a variable parameter in coating production. A mixture consisting of 50% W and 50% Cr as a metal matrix was prepared. Subsequently, WC particles in weight ratios of 25%, 50%, and 75% were added to matrix. As a result, W–Cr metal matrix composite coatings reinforced with WC particles were formed. This study focused on investigation of microstructure, microhardness, phase, and chemical composition as well as corrosion and wear resistance, of the newly formed W–Cr/WC coatings. An instrumented nanoindentation test was also used in this study. As a result of laser beam action, the newly formed coatings had an interesting microstructure and good properties which were improved in comparison to substrate material. It is anticipated that the resulting coatings, depending on the treatment parameters (e.g., W–Cr/WC powder mixture) used, can be successfully applied to metal forming or foundry tools.