The present study was conducted to compare the cleaning efficacy (debris and smear layer removal) of hand and two NiTi rotary instrumentation systems (K3 and ProTaper).
316L stainless steel is a common biomedical material. Currently, biomedical parts are produced through powder injection molding (PIM). Carbon control is the most critical in PIM. Improper debinding can significantly change the properties of the final product. In this work, thermal debinding and sintering were performed in two different furnaces (i.e. laboratory and commercially available furnaces) to study the mechanical properties and corrosion resistance. Debounded samples were sintered in different atmospheres. The samples sintered in inert gas showed enhanced mechanical properties compared with wrought 316L stainless steel and higher corrosion rate than those sintered in the vacuum furnace. The densification and tensile strength of the hydrogen sintered samples increased up to 3% and 51%, respectively, compared with those of the vacuum-sintered samples. However, the samples sintered in inert gas also exhibited reduced ductility and corrosion resistance. This finding is attributed to the presence of residual carbon in debonded samples during debinding.
The combination of metallic bio-inert material, stainless-steel 316L (SS316L) and a bio-active material, hydroxyapatite (HA) can produce a composite which has superior properties for orthopaedic applications. The main objective of this study is to investigate the effects of sintering temperature and holding time on the physical and mechanical properties of the sintered part. 50wt.% SS316L and 50wt.% HA were mixed with a binder system of palm stearin (PS) and polyethylene (PE) at 61 vol.% powder loading. Rheological properties show a pseudo-plastic behaviour of the feedstock, where viscosity decreases with increasing shear rate. The feedstock was injection moulded into a tensile bar shape while thermal debinding was carried out at 320°C and 500°C. The brown parts were sintered at 1000, 1100, 1200 and 1300°C, with three different sintering times of 1, 3 and 5 hours in the furnace. It was found that the highest sintered density measured was 95.61% of the theoretical density. In addition, the highest hardness and Young's modulus measured were 150.45 HV and 52.61 GPa respectively, which are higher than those of human bone. The lowest percentage of carbon content was 0.022wt.% given by the sample sintered at 1300°C for 1 hour. Therefore, SS316L/HA composite with good mechanical and physical properties was successfully produced through the PIM process.
Microbial fuel cells (MFCs) have a high potential application for simultaneous wastewater treatment and electricity
generation. However, the choice of the electrode material and its design is critical and directly affect their performance.
As an electrode of MFCs, the anode material with surface modifications is an attractive strategy to improve the power
output. In this study, stainless steel (SS) and carbon steel (CS) was chosen as a metal anode, while graphite felt (GF)
was used as a common anode. Heat treatment was performed to convert SS, CS and GF into efficient anodes for MFCs.
The maximum current density and power density of the MFC-SS were achieved up till 762.14 mA/m2
and 827.25 mW/m2
,
respectively, which were higher than MFC-CS (641.95 mA/m2
and 260.14 mW/m2
) and MFC-GF (728.30 mA/m2
and 307.89
mW/m2
). Electrochemical impedance spectroscopy of MFC-SS showed better catalytic activity compared to MFC-CS and
MFC-GF anode, also supported by cyclic voltammetry test.
Austenitic stainless steels of grade 304 were exposed to dry (Ar-75%CO2) and wet (Ar-75%CO2-12%H2O) environments at 700oC. This experimental setup involved horizontal tube furnace connected to CO2 gas and water vapour facilities. X-ray diffraction (XRD) technique, variable pressure-scanning electron microscope (VP-SEM) and optical microscope techniques were used to characterize the products of corrosion. The results of XRD showed that the phase of oxide layers consists of Cr2O3 and NiCr2O4 in dry CO2, meanwhile Fe2O3, Cr2O3, Fe0.56Ni0.34, Fe3O4 were identified in wet condition after 50 h. Adding 12%H2O in Ar-75%CO2 leads significantly in weight change occurred at 10 h exposure. However, after 20 h, the weight gain was decreased due to spallation of the oxide scale. The addition of water vapour accelerates the oxidation rate on the steel than that in dry condition. Morphologies and growth kinetics of these oxides vary with reaction condition. The oxidation behaviour at different times of exposure and the effect of water vapour were discussed in correlation with the microstructure of the oxides.
Corrosion is a natural deterioration process that destructs metal surface. Metal of highly
protected by passivation layer such as Stainless Steel 316L also undergoes pitting corrosion
when continuously exposed to aggressive environment. To overcome this phenomenon, application
of epoxy based coating with addition of zinc oxide- poly (3,4-ethylenedioxythiophene)
doped with poly (styrene sulphonate) hybrid nanocomposite additive was introduced as
paint/metal surface coating. The compatibility between these two materials as additive
was studied by Fourier Transform Infrared Spectroscopy (FTIR), X-ray Diffraction (XRD),
Field Emission Scanning Electron Microscopy/Energy-Dispersive X-ray spectroscopy (FESEM/EDX)
and Transmission Electron Microscopy (TEM) analysis. The effect of nanocomposite
wt.% in epoxy based coating with immersion duration in real environment on corrosion
protection performance was analyzed through potentiodynamic polarization analysis. The
main finding showed that addition of hybrid nanocomposite had increased corrosion protection
yet enhanced corrosion process when excess additives was loaded into epoxy coating.
Addition of 2 wt.% ZnO-PEDOT:PSS was found significantly provided optimum corrosion
protection to stainless steel 316L as the corrosion rate for 0 day, 15 days and 30 days of
immersion duration is 0.0022 mm/yr, 0.0004 mm/yr and 0.0015 mm/yr; respectively.
OBJECTIVE: To compare the clinical performance of nickel titanium (NiTi) versus stainless steel (SS) springs during orthodontic space closure.
DESIGN: Two-centre parallel group randomized clinical trial.
SETTING: Orthodontic Department University of Manchester Dental Hospital and Orthodontic Department Countess of Chester Hospital, United Kingdom.
SUBJECTS AND METHODS: Forty orthodontic patients requiring fixed appliance treatment were enrolled, each being randomly allocated into either NiTi (n = 19) or SS groups (n = 21). Study models were constructed at the start of the space closure phase (T0) and following the completion of space closure (T1). The rate of space closure achieved for each patient was calculated by taking an average measurement from the tip of the canine to the mesiobuccal groove on the first permanent molar of each quadrant.
RESULTS: The study was terminated early due to time constraints. Only 30 patients completed, 15 in each study group. There was no statistically significant difference between the amounts of space closed (mean difference 0.17 mm (95%CI -0.99 to 1.34; P = 0.76)). The mean rate of space closure for NiTi coil springs was 0.58 mm/4 weeks (SD 0.24) and 0.85 mm/4 weeks (SD 0.36) for the stainless steel springs. There was a statistically significant difference between the two groups (P = 0.024), in favour of the stainless steel springs, when the mean values per patient were compared.
CONCLUSIONS: Our study shows that stainless steel springs are clinically effective; these springs produce as much space closure as their more expensive rivals, the NiTi springs.
The current work is an attempt to reduce friction coefficient of the treated betelnut fibre reinforced polyester (T-BFRP) composites by aging them in twelve different solutions with different kinematic viscosities. The test will be performed on a pin on disc (POD) wear test rig using different applied loads (5⁻30 N), different sliding distances (0⁻6.72 km) at sliding speed of 2.8 m/s subjected to a smooth stainless steel counterface (AISI-304). Different orientations of the fibre mats such as anti-parallel (AP) and parallel (P) orientations subjected to the rotating counterface will be considered. The worn surfaces were examined through optical microscopy imaging and it was found that the aged specimens had significantly lower damages as compared to neat polyester (NP) and the unaged samples. Besides, P-O samples revealed lower friction coefficients as compared to AP-O, i.e., reduction was about 24.71%. Interestingly, aging solutions with lower kinematic viscosities revealed lower friction coefficients of the aged T-BFRP composites when compared to the ones aged in higher kinematic viscosities.
This article describes the development of a partially degradable metal bone pin, proposed to minimize the occurrence of bone refracture by avoiding the creation of holes in the bone after pin removal procedure. The pin was made by friction welding and composed of two parts: the degradable part that remains in the bone and the nondegradable part that will be removed as usual. Rods of stainless steel 316L (nondegradable) and pure iron (degradable) were friction welded at the optimum parameters: forging pressure = 33.2 kPa, friction time = 25 s, burn-off length = 15 mm, and heat input = 4.58 J/s. The optimum tensile strength and elongation was registered at 666 MPa and 13%, respectively. A spiral defect formation was identified as the cause for the ductile fracture of the weld joint. A 40-µm wide intermetallic zone was identified along the fusion line having a distinct composition of Cr, Ni, and Mo. The corrosion rate of the pin gradually decreased from the undeformed zone of pure iron to the undeformed zone of stainless steel 316L. All metallurgical zones of the pin showed no toxic effect toward normal human osteoblast cells, confirming the ppb level of released Cr and Ni detected in the cell media were tolerable.
Stainless steels are increasingly used in construction today, especially in harsh environments, in which steel corrosion commonly occurs. Cold-formed stainless steel structures are currently increasing in popularity because of its efficiency in load-bearing capacity and its appealing architectural appearance. Cold-rolling and press-braking are the cold-working processes used in the forming of stainless steel sections. Press braking can produce large cross-sections from thin to thick-walled sections compared to cold-rolling. Cold-forming in press-braked sections significantly affect member behaviour and joints; therefore, they have attained great attention from many researchers to initiate investigations on those effects. This paper examines the behaviour of residual stress distribution of stainless steel press-braked sections by implementing three-dimensional finite element (3D-FE) technique. The study proposed a full finite element procedure to predict the residual stresses starting from coiling-uncoiling to press-braking. This work considered material anisotropy to examine its effect on the residual stress distribution. The technique adopted was compared with different finite element techniques in the literature. This study also provided a parametric study for three corner radius-to-thickness ratios looking at the through-thickness residual stress distribution of four stainless steels (i.e., ferritic, austenitic, duplex, lean duplex) in which have their own chemical composition. In conclusion, the comparison showed that the adopted technique provides a detailed prediction of residual stress distribution. The influence of geometrical aspects is more pronounced than the material properties. Neglecting the material anisotropy shows higher shifting in the neutral axis. The parametric study showed that all stainless steel types have the same stress through-thickness distribution. Moreover, R/t ratios' effect is insignificant in all transverse residual stress distributions, but a slight change to R/t ratios can affect the longitudinal residual stress distribution.
A systematic study to assess the concentration of radionuclides in primary coolant and associated water samples from the operation of a TRIGA Mark II reactor has been carried out. The samples were transferred into appropriate counting container and were counted by efficiency-calibrated gamma spectrometer systems for several hours to obtain statistically adequate data for qualitative and quantitative evaluation of the radioactive materials presence. The primary coolant was found to contain various gamma emitting radionuclides including 24Na, 41Ar, 42K, 51Cr, , 54Mn, 56Mn, 60Co, 99mTc, 122Sb, 124Sb and 187W. Most of the detected radionuclides were inferred to be originated from activation products of (n,) nuclear reactions of elements of reactor components such as stainless steel and aluminium alloy used in the reactor system. The study confirms the integrity of the reactor system with no apparent release of any fission products radionuclide into the coolant water system.
This research investigates and analyzes wear properties of 316 stainless steel before and after applying paste boronizing process and to investigate the effect of shot blasting process in enhancing boron dispersion into the steel. In order to enhance the boron dispersion into 316 stainless steel, surface deformation method by shot blasting process was deployed. Boronizing treatment was conducted using paste medium for 8 hours under two different temperatures which were 8500 C and 9500 C. Wear behaviour was evaluated using pin-on-disc test for abrasion properties. The analysis on microstructure, X-ray Diffraction (XRD) and density were also carried out before and after applying boronizing treatment. Boronizing process that had been carried out on 316 stainless steel increases the wear resistance of the steel compared to the unboronized 316 stainless steel. The effect of boronizing treatment together with the shot blasting process give a greater impact in increasing the wear resistance of 316 stainless steel. This is mainly because shot blasted samples initiated surface deformation that helped more boron dispersion due to dislocation of atom on the deformed surface. Increasing the boronizing temperature also increases the wear resistance of 316 stainless steel. In industrial application, the usage of the components that have been fabricated using the improved 316 stainless steel can be maximized because repair and replacement of the components can be reduced as a result of improved wear resistance of the 316 stainless steel.
Three different designs of heat exchanger, V-groove, honeycomb and stainless steel wool had been tested to study their effectiveness in improving the overall performance of a photovoltaic/thermal (PV/T) air base solar collector. Heat exchangers were installed horizontally into the channel located at the back side of the PV module. The system was tested at irradiance of 828 W/m2 with mass flow rate spanning from 0.02 kg/s to 0.13 kg/s. It was observed that at mass flow rate of 0.11 kg/s, the maximum thermal efficiency of the system with V-groove is 71%, stainless steel wool is 86% and honeycomb is 87%. The electrical efficiency of the systems is 7.04%, 6.88% and 7.13%, respectively. The experimental results showed that honeycomb design is the most efficient design as heat exchanger. The design which is simple and compact is suitable for building integration.
This report aimed to describe an effective biomechanics to control the upper incisors inclination during the
correction of gummy smile with bimaxillary proclinations. A 14-year-old female presented with a Class II
division I incisor relationship complicated with bimaxillary proclination on a Class 2 skeletal base. The lips
were incompetent, showing 7 mm of upper incisors at rest and 5mm maxillary gingival display on smiling
with normal upper lip length. Treatment involved extraction of all first permanent premolars followed by
upper and lower fixed appliances. Intrusion of the upper incisors with controlled labial crown torque was
accomplished with mini-implant anchorage placed bilaterally on the infrazygomatic crests with the retraction
forces above the centre of resistance using 0.019x0.025-in stainless steel archwire in 0.022-in slot. The
0.019x0.025-in stainless steel archwire in 0.022-in slot provided the vertical play to favour lingual crown
tipping despite having forces above the centre of resistance for concurrent anterior segment intrusion.
In this study, two nickel based electrodes were prepared; nickel foil and nickel-polyvinylchloride (Ni-PVC), in order to study their electrochemical behavior using cyclic voltammetry, CV and chronocoulometry, CC. Ni electrode was prepared from Ni metal foil while Ni-PVC electrode was prepared by mixing a weighed portion of Ni powder and PVC in THF solvent, swirled until the suspension was homogeneous and drying the suspension in an oven at 50oC for 3 h. The dry sample was then placed in a 1 cm diameter stainless steel mould and pressed at 10 ton/cm2. From CV data, Ni-PVC electrode showed a better electrochemical behavior compared to Ni metal foil electrode. The use of Ni-PVC electrode at higher concentration of supporting electrolyte (1.0 M KOH) was better than at lower concentration of the same supporting electrolyte in electroxidation of ethanol. In addition to acetic acid, the oxidation of ethanol also produced ethyl acetate and acetaldehyde.
This study compared the surface roughness of selected tooth coloured restorative materials that were polished according to manufacturers’ instructions and Sof-Lex. It also assessed the surface roughness of polished materials after thermocycling.Filtek Z350XT, Beautifil-Bulk Restorative and Cention N, were used in this study. A stainless steel mould (10mm diameter x 2mm height) was used to fabricate 75 cylindrical specimens: 15 Filtek Z350XT (FZ), 30 Beautifil-Bulk Restorative (BB) and 30 Cention N (CN). All 15 FZ specimens were polished with Sof-Lex. Fifteen BB and CN specimens were polished according to manufacturers’ instructions. The remaining fifteen BB and CN specimens were polished using Sof-Lex. All the specimens were subjected to thermocycling (1000 cycles). Surface roughness was assessed quantitatively with profilometry after specimen preparation (Mylar stage), polishingand thermocycling. Data were analysed using SPSS version 25.0 at α=0.05. When polished according to manufacturers’ instructions, BB had the lowest mean surface roughness (Ra) values (0.13±0.01μm) followed sequentially by CN (0.14±0.03μm) and FZ (0.15±0.02μm). The differences were not statistically significant. When polished with Sof-Lex, BB exhibited the smoothest surface (0.116±0.03μm) followed sequentially by and FZ (0.150±0.02μm) and CN (0.157±0.02μm). Thermocycling caused an increase in the Ra. The differences were statistically significant. All materials tested had Ra values below the threshold value of 0.2 μm at Mylar stage and after polishing with their recommended polishing system and Sof-Lex. Thermocycling produced rougher surfaces that did not exceed the threshold Ra value. Polishability was material dependent.
This study focuses on the effect of boronizing medium on the boride layer thickness of pack boronized 304 stainless steel after surface modification. Pack boronizing treatment was conducted in temperature of 900oC for a duration of eight hours. The treatment was performed using two different boronizing mediums which are powder and paste inside a tight box in an induction furnace. The characteristics of the samples were then observed using optical microscopy and XRD analyser. The thickness of boride layer was then measured using MPS digital image analysis software. The results showed that boronizing medium significantly affected the thickness of boride layer as paste boronized samples exhibited thicker boride layer thickness. The enhancement was mainly due to the size of boron particle in the paste medium which was smaller than powder medium that enabled better diffusion. It is expected that the enhancement of the boride layer thickness would result in further improvement of the mechanical and wear properties of this material.
Chlorhexidine (CHX) is known for its high antibacterial substantivity and is suitable for use to bio-inert medical devices due to its long-term antibacterial efficacy. However, CHX molecules require a crosslinking film to be stably immobilized on bio-inert metal surfaces. Therefore, polydopamine (PDA) was utilized in this study to immobilize CHX on the surface of 316L type stainless steel (SS316L). The SS316L disks were pre-treated, modified with PDA film and immobilized with different concentrations of CHX (10mM-50mM). The disks were then subjected to various surface characterization analyses (ATR-FTIR, XPS, ToF-SIMS, SEM and contact angle measurement) and tested for their cytocompatibility with human skin fibroblast (HSF) cells and antibacterial activity against Escherichia coli and Staphylococcus aureus. The results demonstrated the formation of a thin PDA film on the SS316L surface, which acted as a crosslinking medium between the metal and CHX. CHX was immobilized via a reduction process that covalently linked the CHX molecules with the functional group of PDA. The immobilization of CHX increased the hydrophobicity of the disk surfaces. Despite this property, a low concentration of CHX optimized the viability of HSF cells without disrupting the morphology of adherent cells. The immobilized disks also demonstrated high antibacterial efficacy against both bacteria, even at a low concentration of CHX. This study demonstrates a strong beneficial effect of the crosslinked PDA film in immobilizing CHX on bio-inert metal, and these materials are applicable in medical devices. Specifically, the coating will restrain bacterial proliferation without suffocating nearby tissues.
Immobilization of chlorhexidine (CHX) on stainless steel 316L (SS316L), assisted by a polydopamine film as an intermediate layer is projected as an approach in combating infection while aiding bone regeneration for coating development on orthopedic and dental implants. This study aimed to investigate the ability of CHX coating to promote apatite layer, osteoblast cells viability, adhesion, osteogenic differentiation and mineralization. Stainless steel 316L disks were pre-treated, grafted with a polydopamine film and immobilized with different concentrations of CHX (10-30mM). The apatite layer formation was determined through an in vitro simulated body fluid (SBF) test by ATR-FTIR and SEM-EDX analyses. The osteoblastic evaluations including cells viability, cells adhesion, osteogenic differentiation and mineralization were assessed with human fetal osteoblast cells through MTT assay, morphology evaluation under FESEM, ALP enzyme activity and Alizarin Red S assay. The apatite layer was successfully formed on the CHX coated disks, demonstrating potential excellent bioactivity property. The CHX coatings were biocompatible with the osteoblast cells at low CHX concentration (<20mM) with good adhesion on the metal surfaces. The increment of ALP activity and calcium deposition testified that the CHX coated disks able to support osteoblastic maturation and mineralization. These capabilities give a promising value to the CHX coating to be implied in bone regeneration area.