Abstract Objectives This work focuses on a titanium alloy implants incorporating a gradient of porosity, from the inner core to the outer surface, obtained by laser sintering of metal powder. Surface ...appearance, microstructure, composition, mechanical properties and fractography were evaluated. Methods All the specimens were prepared by a selective laser sintering procedure using a Ti–6Al–4V alloy powder with a particle size of 1–10 μm. The morphological and chemical analyses were performed by SEM and energy dispersive X-ray spectroscopy. The flexure strength was determined by a three-point bend test using a universal testing machine. The surface roughness was investigated using a confocal scanning laser microscope. The surface roughness variation was statistically evaluated by use of a Chi square test. A p value of <0.05 was considered statistically significant. Results The original surface microstructure consisted of roughly spherical particles, diameter range 5–50 μm. After exposure to hydrofluoric acid some of these were removed and the microsphere diameter then ranged from 5.1 μm to 26.8 μm. Following an organic acid treatment, particles were replaced by grooves 14.6–152.5 μm in width and 21.4–102.4 μm depth. The metal core consisted of columnar beta grains with alpha and beta laths within the grains. The alloy was composed of 90.08% Ti, 5.67% Al and 4.25% V. The Young's modulus of the inner core material was 104 ± 7.7 GPa; while that of the outer porous material was 77 ± 3.5 GPa. The fracture face showed a dimpled appearance typical of ductile fracture. Significance In conclusion, laser metal sintering proved to be an efficient means of construction of dental implants with a functionally graded material which is better adapted to the elastic properties of the bone. Such implants should minimize stress shielding effects and improve long-term performance.
Biofilm accumulation on biomaterial surfaces is a major health concern and significant research efforts are directed towards producing biofilm resistant surfaces and developing biofilm removal ...techniques. To accurately evaluate biofilm growth and disruption on surfaces, accurate methods which give quantitative information on biofilm area are needed, as current methods are indirect and inaccurate. We demonstrate the use of machine learning algorithms to segment biofilm from scanning electron microscopy images. A case study showing disruption of biofilm from rough dental implant surfaces using cavitation bubbles from an ultrasonic scaler is used to validate the imaging and analysis protocol developed. Streptococcus mutans biofilm was disrupted from sandblasted, acid etched (SLA) Ti discs and polished Ti discs. Significant biofilm removal occurred due to cavitation from ultrasonic scaling (p < 0.001). The mean sensitivity and specificity values for segmentation of the SLA surface images were 0.80 ± 0.18 and 0.62 ± 0.20 respectively and 0.74 ± 0.13 and 0.86 ± 0.09 respectively for polished surfaces. Cavitation has potential to be used as a novel way to clean dental implants. This imaging and analysis method will be of value to other researchers and manufacturers wishing to study biofilm growth and removal.
•Biofilm is cleaned through ultrasonic cavitation bubbles contacting the surface.•Ultrasonic scalers produce chaotic shape oscillations which disrupt biofilm.•Cavitation clouds and acoustic streaming ...also contribute to biofilm disruption.
Bacterial biofilm accumulation is problematic in many areas, leading to biofouling in the marine environment and the food industry, and infections in healthcare. Physical disruption of biofilms has become an important area of research. In dentistry, biofilm removal is essential to maintain health. The aim of this study is to observe biofilm disruption due to cavitation generated by a dental ultrasonic scaler (P5XS, Acteon) using a high speed camera and determine how this is achieved. Streptococcus sanguinis biofilm was grown on Thermanox™ coverslips (Nunc, USA) for 4 days. After fixing and staining with crystal violet, biofilm removal was imaged using a high speed camera (AX200, Photron). An ultrasonic scaler tip (tip 10P) was held 2 mm away from the biofilm and operated for 2 s. Bubble oscillations were observed from high speed image sequences and image analysis was used to track bubble motion and calculate changes in bubble radius and velocity on the surface. The results demonstrate that most of the biofilm disruption occurs through cavitation bubbles contacting the surface within 2 s, whether individually or in cavitation clouds. Cleaning occurs through shape oscillating microbubbles on the surface as well as through fluid flow.
Effective biofilm removal from surfaces in the mouth is a clinical challenge. Cavitation bubbles generated around a dental ultrasonic scaler are being investigated as a method to remove biofilms ...effectively. It is not known how parameters such as surface roughness and instrument distance from biofilm affect the removal. We grew Strepotococcus sanguinis biofilms on coverslips and titanium discs with varying surface roughness (between 0.02–3.15 μm). Experimental studies were carried out for the biofilm removal using high speed imaging and image analysis to calculate the area of biofilm removed at varying ultrasonic scaler standoff distances from the biofilm. We found that surface roughness up to 2 μm does not adversely affect biofilm removal but a surface roughness of 3 μm caused less biofilm removal. The standoff distance also has different effects depending on the surface roughness but overall a distance of 1 mm is just as effective as a distance of 0.5 mm. The results show significant biofilm removal due to an ultrasonic scaler tip operating for only 2s versus 15-60s in previous studies. The technique developed for high speed imaging and image analysis of biofilm removal can be used to investigate physical biofilm disruption from biomaterial surfaces in other fields.
Antibacterial surface modification of biomedical materials has evolved as a potentially effective method for preventing bacterial proliferation on the surfaces of devices. However, thin antibacterial ...coatings or modified layers can be easily worn down when interacting with other surfaces in relative motion, thus leading to a low durability of the antibacterial surface. To this end, novel biomaterial surfaces with antibacterial Ag agents and a wear-resistant S-phase have been generated on stainless steel by duplex plasma silvering–nitriding techniques for application to load-bearing medical devices. The chemical composition, microstructure, surface topography, roughness and wettability of SS surfaces were characterised using glow discharge optical emission spectroscopy, energy-dispersive spectroscopy/wavelength dispersive spectrometry (WDS), X-ray diffraction, atomic force microscopy and a contact angle goniometer. Optimal surface design for high antimicrobial activity and prolonged durability has been achieved, as evidenced by rapid bacterial killing rates (within 6
h), an ultra hard matrix (875
±
25
Hv), high load-bearing capacity (critical load 37
N) and excellent wear resistance (wear rate 4.9
×
10
−6
mm
3
m
−1). Ag embedded in the hard substrate of fcc compounds M
4N (M
=
Fe, Cr, Ag, etc.) and the expanded fcc nitrogen S-phase shows deep infiltration of 6
±
1
μm, and provides bactericidal activity against both Gram-negative
Escherichia coli NCTC 10418 and Gram-positive
Staphylococcus epidermidis NCTC 11047 of over 97% and 90%, respectively, within 6
h. The presence of silver in the surface before and after scratching under a progressive load applied up to 60
N using a diamond stylus was confirmed by WDS.
Abstract Objectives Functionalised silica sub-micron particles are being investigated as a method of delivering antimicrobials and remineralisation agents into dentinal tubules. However, their ...methods of application are not optimised, resulting in shallow penetration and aggregation. The aim of this study is to investigate the impact of cavitation occurring around ultrasonic scalers for enhancing particle penetration into dentinal tubules. Methods Dentine slices were prepared from premolar teeth. Silica sub-micron particles were prepared in water or acetone. Cavitation from an ultrasonic scaler (Satelec P5 Newtron, Acteon, France) was applied to dentine slices immersed inside the sub-micron particle solutions. Samples were imaged with scanning electron microscopy (SEM) to assess tubule occlusion and particle penetration. Results Qualitative observations of SEM images showed some tubule occlusion. The particles could penetrate inside the tubules up to 60 μm when there was no cavitation and up to ∼180 μm when there was cavitation. Conclusions The cavitation bubbles produced from an ultrasonic scaler may be used to deliver sub-micron particles into dentine. This method has the potential to deliver such particles deeper into the dentinal tubules. Clinical significance Cavitation from a clinical ultrasonic scaler may enhance penetration of sub-micron particles into dentinal tubules. This can aid in the development of novel methods for delivering therapeutic clinical materials for hypersensitivity relief and treatment of dentinal caries.
•Cavitation bubbles are involved in the removal of bacterial biofilm around dental ultrasonic scalers.•The maximum radius of these bubbles ranged from 40 to 80μm.•Able to track bubbles forming around ...dental ultrasonic scalers.•Image analysis and manual tracking enabled bubble radius and speed to be calculated in their life cycle.
Cavitation is a potentially effective and less damaging method of removing biofilm from biomaterial surfaces. The aim of this study is to characterise individual microbubbles around ultrasonic scaler tips using high speed imaging and image processing. This information will provide improved understanding on the disruption of dental biofilm and give insights into how the instruments can be optimised for ultrasonic cleaning. Individual cavitation microbubbles around ultrasonic scalers were analysed using high speed recordings up to a million frames per second with image processing of the bubble movement. The radius and rate of bubble growth together with the collapse was calculated by tracking multiple points on bubbles over time. The tracking method to determine bubble speed demonstrated good inter-rater reliability (intra class correlation coefficient: 0.993) and can therefore be a useful method to apply in future studies. The bubble speed increased over its oscillation cycle and a maximum of 27ms−1 was recorded during the collapse phase. The maximum bubble radii ranged from 40 to 80μm. Bubble growth was observed when the ultrasonic scaler tip receded from an area and similarly bubble collapse was observed when the tip moved towards an area, corresponding to locations of low pressure around the scaler tip. Previous work shows that this cavitation is involved in biofilm removal. Future experimental work can be based on these findings by using the protocols developed to experimentally analyse cavitation around various clinical instruments and comparing with theoretical calculations. This will help to determine the main cleaning mechanisms of cavitation and how clinical instruments such as ultrasonic scalers can be optimised.
Highlights • Ultrasonic tip vibrations depend on tip shape, design and generator power. • Water running over the tip and loads suppress tip vibrations. • Clinical loads with high power settings make ...the tips behave unpredictably. • Low loads yield a steady decrease of tip vibration with increasing load.
A tale of two clades: monkeypox viruses Likos, Anna M; Sammons, Scott A; Olson, Victoria A ...
Journal of general virology,
10/2005, Volume:
86, Issue:
Pt 10
Journal Article
Peer reviewed
Open access
Human monkeypox was first recognized outside Africa in 2003 during an outbreak in the USA that was traced to imported monkeypox virus (MPXV)-infected West African rodents. Unlike the smallpox-like ...disease described in the Democratic Republic of the Congo (DRC; a Congo Basin country), disease in the USA appeared milder. Here, analyses compared clinical, laboratory and epidemiological features of confirmed human monkeypox case-patients, using data from outbreaks in the USA and the Congo Basin, and the results suggested that human disease pathogenicity was associated with the viral strain. Genomic sequencing of USA, Western and Central African MPXV isolates confirmed the existence of two MPXV clades. A comparison of open reading frames between MPXV clades permitted prediction of viral proteins that could cause the observed differences in human pathogenicity between these two clades. Understanding the molecular pathogenesis and clinical and epidemiological properties of MPXV can improve monkeypox prevention and control.
Tissue engineering offers a promising alternative to the use of autografts in the treatment of ligament injuries. However, current approaches using only biodegradable materials have insufficient ...mechanical strength for load bearing applications. In this research, hybrid bio-artificial ligaments were fabricated using a combination of a titanium alloy spring and a fibrin gel/fibroblast construct. The ends of the ligament prosthesis were incorporated into brushite cement anchors to allow fusion with the host bone. Cell attachment to the titanium spring was examined using scanning electron microscopy and fluorescent staining of cells. The unreinforced constructs were observed to fail at the anchor-ligament junction, while the titanium spring reinforcement was found to assist in even transmission of the load to the ligament, and hence to provide a means of load sharing between the biological construct and the spring. As a result, the reinforced construct failed primarily in the soft tissue region. The good load distribution features from the mechanical data was attributed to the good cellular level adhesion to, and alignment along the coiling of, the length of the spring reinforcement. Incorporation of a biocompatible reinforcement in conjunction with a tissue engineered construct gave improved load distribution, reducing stress concentrations, and significantly increased the ultimate strength at failure. The results suggest that the hybrid approach used here shows promise in developing improved therapies for connective tissue injuries.
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