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The heparan sulfate (HS)-rich extracellular matrix (ECM) serves as an initial interaction site for the homotrimeric spike (S) protein of SARS-CoV-2 to facilitate subsequent docking to angiotensin-converting enzyme 2 (ACE2) receptors and cellular infection. More recent variants, notably Omicron, have evolved by swapping several amino acids to positively charged residues to enhance the interaction of the S-protein trimer with the negatively charged HS. However, these enhanced interactions may reduce Omicron's ability to move through the HS-rich ECM to effectively find ACE2 receptors and infect cells, raising the question of how to mechanistically explain HS-associated viral movement. In this work, we show that Omicron S proteins have evolved to balance HS interaction stability and dynamics, resulting in enhanced mobility on an HS-functionalized artificial matrix. This property is achieved by the ability of Omicron S-proteins to cross-link at least two HS chains, allowing direct S-protein switching between chains as a prerequisite for cell surface mobility. Optimized HS interactions can be targeted pharmaceutically, as an HS mimetic significantly suppressed surface binding and cellular infection specifically of the Omicron variant. These findings suggest a robust way to interfere with SARS-CoV-2 Omicron infection and potentially future variants., Competing Interests: Declarations. Competing interests: The authors declare no competing interests., (© 2024. The Author(s).)

Morphogens determine cellular differentiation in many developing tissues in a concentration dependent manner. As a central model for gradient formation during animal development, Hedgehog (Hh) morphogens spread away from their source to direct growth and pattern formation in the Drosophila wing disc. Although heparan sulfate (HS) expression in the disc is essential for this process, it is not known whether HS regulates Hh signaling and spread in a direct or in an indirect manner. To answer this question, we systematically screened two composite Hh binding areas for HS in vitro and expressed mutated proteins in the Drosophila wing disc. We found that selectively impaired HS binding of the second site reduced Hh signaling close to the source and caused striking wing mispatterning phenotypes more distant from the source. These observations suggest that HS constrains Hh to the wing disc epithelium in a direct manner, and that interfering with this constriction converts Hh into freely diffusing forms with altered signaling ranges and impaired gradient robustness., Competing Interests: The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest., (Copyright © 2023 Manikowski, Steffes, Froese, Exner, Ehring, Gude, Di Iorio, Wegner and Grobe.)

Cellular differentiation is directly determined by concentration gradients of morphogens. As a central model for gradient formation during development, Hedgehog (Hh) morphogens spread away from their source to direct growth and pattern formation in Drosophila wing and eye discs. What is not known is how extracellular Hh spread is achieved and how it translates into precise gradients. Here we show that two separate binding areas located on opposite sides of the Hh molecule can interact directly and simultaneously with two heparan sulfate (HS) chains to temporarily cross-link the chains. Mutated Hh lacking one fully functional binding site still binds HS but shows reduced HS cross-linking. This, in turn, impairs Hhs ability to switch between both chains in vitro and results in striking Hh gradient hypomorphs in vivo. The speed and propensity of direct Hh switching between HS therefore shapes the Hh gradient, revealing a scalable design principle in morphogen-patterned tissues., (© 2023. The Author(s).)

Rapid advancements of genome sequencing (GS) technologies have enhanced our understanding of the relationship between genes and human disease. To incorporate genomic information into the practice of medicine, new processes for the analysis, reporting, and communication of GS data are needed. Blood samples were collected from adults with a PCR-confirmed SARS-CoV-2 (COVID-19) diagnosis (target N = 1500). GS was performed. Data were filtered and analyzed using custom pipelines and gene panels. We developed unique patient-facing materials, including an online intake survey, group counseling presentation, and consultation letters in addition to a comprehensive GS report. The final report includes results generated from GS data: (1) monogenic disease risks; (2) carrier status; (3) pharmacogenomic variants; (4) polygenic risk scores for common conditions; (5) HLA genotype; (6) genetic ancestry; (7) blood group; and, (8) COVID-19 viral lineage. Participants complete pre-test genetic counseling and confirm preferences for secondary findings before receiving results. Counseling and referrals are initiated for clinically significant findings. We developed a genetic counseling, reporting, and return of results framework that integrates GS information across multiple areas of human health, presenting possibilities for the clinical application of comprehensive GS data in healthy individuals., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Stroke is a leading cause of death and disability worldwide. Women are disproportionately affected by stroke, exhibiting higher mortality and disability rates post-stroke than men. Clinical stroke research has historically included mostly men and studies were not properly designed to perform sex- and gender-based analyses, leading to under-appreciation of differences between men and women in stroke presentation, outcomes, and response to treatment. Reasons for these differences are likely multifactorial; some are due to gender-related factors (i.e. decreased social support, lack of stroke awareness), yet others result from biological differences between sexes. Unlike men, women often present with 'atypical' stroke symptoms. Lack of awareness of 'atypical' presentation has led to delays in hospital arrival, diagnosis, and treatment of women. Differences also extend to carotid atherosclerotic disease, a cause of stroke, where plaques isolated from women are undeniably different in morphology/composition compared to men. As a result, women may require different treatment than men, as evidenced by the fact that they derive less benefit from carotid revascularization than men but more benefit from medical management. Despite this, women are less likely than men to receive medical therapy for cardiovascular risk factor management. This review focuses on the importance of sex and gender in ischaemic stroke and carotid atherosclerotic disease, summarizing the current evidence with respect to (i) stroke incidence, mortality, awareness, and outcomes, (ii) carotid plaque prevalence, morphology and composition, and gene connectivity, (iii) the role of sex hormones and sex chromosomes in atherosclerosis and ischaemic stroke risk, and (iv) carotid disease management., (Published on behalf of the European Society of Cardiology. All rights reserved. © The Author(s) 2021. For permissions, please email: journals.permissions@oup.com.)

Male patients with Fabry disease (FD) are at high risk for the formation of antibodies to recombinant α-galactosidase A (AGAL), used for enzyme replacement therapy. Due to the rapid disease progression, the identification of patients at risk is highly warranted. However, currently suitable references and standardized protocols for anti-drug antibodies (ADA) determination do not exist. Here we generate a comprehensive patient-derived antibody mixture as a reference, allowing ELISA-based quantification of antibody titers from individual blood samples. Serum samples of 22 male patients with FD and ADAs against AGAL were pooled and purified by immune adsorption. ADA-affinities against agalsidase-α, agalsidase-β and Moss-AGAL were measured by quartz crystal microbalance with dissipation monitoring (QCM-D). AGAL-specific immune adsorption generated a polyclonal ADA mixture showing a concentration-dependent binding and inhibition of AGAL. Titers in raw sera and from purified total IgGs (r 2 = 0.9063 and r 2 = 0.8952, both p < 0.0001) correlated with the individual inhibitory capacities of ADAs. QCM-D measurements demonstrated comparable affinities of the reference antibody for agalsidase-α, agalsidase-β and Moss-AGAL (KD: 1.94 ± 0.11 µM, 2.46 ± 0.21 µM, and 1.33 ± 0.09 µM, respectively). The reference antibody allows the ELISA-based ADA titer determination and quantification of absolute concentrations. Furthermore, ADAs from patients with FD have comparable affinities to agalsidase-α, agalsidase-β and Moss-AGAL.

Understanding how emerging influenza viruses recognize host cells is critical in evaluating their zoonotic potential, pathogenicity, and transmissibility between humans. The surface of the influenza virus is covered with hemagglutinin (HA) proteins that can form multiple interactions with sialic acid-terminated glycans on the host cell surface. This multivalent binding affects the selectivity of the virus in ways that cannot be predicted from the individual receptor-ligand interactions alone. Here, we show that the intrinsic structural and energetic differences between the interactions of avian- or human-type receptors with influenza HA translate from individual site affinity and orientation through receptor length and density on the surface into virus avidity and specificity. We introduce a method to measure virus avidity using receptor density gradients. We found that influenza viruses attached stably to a surface at receptor densities that correspond to a minimum number of approximately 8 HA-glycan interactions, but more interactions were required if the receptors were short and human-type. Thus, the avidity and specificity of influenza viruses for a host cell depend not on the sialic acid linkage alone but on a combination of linkage and the length and density of receptors on the cell surface. Our findings suggest that threshold receptor densities play a key role in virus tropism, which is a predicting factor for both their virulence and zoonotic potential., Competing Interests: The authors declare no competing financial interest., (© 2020 American Chemical Society.)

Natural hydrocarbon seeps are ubiquitous along continental margins. Despite their significance, we lack a basic understanding of the long-term temporal variability of seep dynamics, including bubble size, rise velocity, composition, and upwelling and entrainment processes. The shortcoming makes it difficult to constrain the global estimates of oil and gas entering the marine environment. Here we report on a multi-method approach based on optical, acoustic, satellite remote sensing, and simulations, to connect the characteristics of a hydrocarbon seep in the Gulf of Mexico to its footprint on the sea surface. Using an in-situ camera, bubble dynamics at the source were measured every 6 h over 153 days and the integrated total hydrocarbon release volume was estimated as 53 m 3 . The vertical velocity was acoustically measured at 20 m above bed (mab) and found to be approximately 40% less than the dispersed-phase at the source, indicating that the measured values are reflecting the plume continuous-phase flow. Numerical simulations predict that the oily bubbles with diameters larger than 8 mm reach the surface with a small footprint, i.e. forming an oil slick origin, deflection of which with wind and surface current leads to the formation of an oil slick on the surface. Nineteen SAR images are used to estimate the oil seepage rate from GC600 for 2017 giving an average discharge of 14.4 cm 3 /s.

Thrombocytopenia is a common complication of influenza virus infection, and its severity predicts the clinical outcome of critically ill patients. The underlying cause(s) remain incompletely understood. In this study, in patients with an influenza A/H1N1 virus infection, viral load and platelet count correlated inversely during the acute infection phase. We confirmed this finding in a ferret model of influenza virus infection. In these animals, platelet count decreased with the degree of virus pathogenicity varying from 0% in animals infected with the influenza A/H3N2 virus, to 22% in those with the pandemic influenza A/H1N1 virus, up to 62% in animals with a highly pathogenic A/H5N1 virus infection. This thrombocytopenia is associated with virus-containing platelets that circulate in the blood. Uptake of influenza virus particles by platelets requires binding to sialoglycans and results in the removal of sialic acids by the virus neuraminidase, a trigger for hepatic clearance of platelets. We propose the clearance of influenza virus by platelets as a paradigm. These insights clarify the pathophysiology of influenza virus infection and show how severe respiratory infections, including COVID-19, may propagate thrombocytopenia and/or thromboembolic complications., (© 2020 by The American Society of Hematology.)

The development of model systems that mimic biological interactions and allow the control of both receptor and ligand densities, is essential for a better understanding of biomolecular processes, such as the recruitment of receptors at interfaces, at the molecular level. Here we report a model system based on supported lipid bilayers (SLBs) for the investigation of the clustering of receptors at their interface. Biotinylated SLBs, used as cell membrane mimics, were functionalized with streptavidin (SAv), used here as receptor. Subsequently, biotinylated small (SUVs) and giant (GUVs) unilamellar vesicles were bound to the SAv-functionalized SLBs by multivalent interactions and found to induce the recruitment of both SAv on the SLB surface and the biotin moieties in the vesicles. The recruitment of receptors was investigated with quartz crystal microbalance with dissipation monitoring (QCM-D), which allowed the identification of the biotin and SAv densities necessary to obtain receptor recruitment. At approx. 0.6% of biotin in the vesicles, a transition between dense and low vesicle packing was observed, which coincided with the transitions between recruitment in the vesicles vs. recruitment in the SLB and between full and partial use of the biotin moieties in the vesicle. Direct optical visualization of the clustering at the interface of individual GUVs with the SLB platform was achieved with fluorescence microscopy, showing recruitment of SAv at the contact area as well as the deformation of the vesicles upon binding. Different vesicle binding regimes were observed for lower and higher biotin densities in the vesicles and at the SLBs. A more quantitative analysis of the molecular parameters implied in the interaction, indicated that approx. 10% of the vesicle area constitutes the contact area. Moreover, the SUV binding and recruitment appeared to be fast on the analysis time scale, whereas the binding of GUVs is slower due to the larger SLB area over which SAv recruitment needs to occur. The mechanisms revealed in this study may provide insight in biological processes in which recruitment occurs., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

In the study of multivalent interactions at interfaces, as occur for example at cell membranes, the density of the ligands or receptors displayed at the interface plays a pivotal role, affecting both the overall binding affinities and the valencies involved in the interactions. In order to control the ligand density at the interface, several approaches have been developed, and they concern the functionalization of a wide range of materials. Here, different methods employed in the modification of surfaces with controlled densities of ligands are being reviewed. Examples of such methods encompass the formation of self-assembled monolayers (SAMs), supported lipid bilayers (SLBs) and polymeric layers on surfaces. Particular emphasis is given to the methods employed in the study of different types of multivalent biological interactions occurring at the functionalized surfaces and their working principles., Competing Interests: The authors declare no conflict of interest., (©2020 The Authors. Published by Wiley-VCH Verlag GmbH & Co. KGaA.)

Biomolecules are immobilized onto surfaces employing the fast and stable adsorption of poly-l-lysine (PLL) polymers and the versatile copper-free click chemistry reactions. This method provides the combined advantages of versatile surface adsorption with density control using polyelectrolytes and of the covalent and orthogonal immobilization of biomolecules with higher reaction rates and improved yields of click chemistry. Using DNA attachment as a proof of concept, control over the DNA probe density and applicability in electrochemical detection are presented., Competing Interests: There are no conflicts to declare., (This journal is © The Royal Society of Chemistry.)

We conducted a free-water mass balance-based study to address the rate of metabolism and net carbon exchange for the tidal wetland and estuarine portion of the coastal ocean and the uncertainties associated with this approach were assessed. We measured open water diurnal O 2 and dissolved inorganic carbon (DIC) dynamics seasonally in a salt marsh-estuary in Georgia, U.S.A. with a focus on the marsh-estuary linkage associated with tidal flooding. We observed that the overall estuarine system was a net source of CO 2 to the atmosphere and coastal ocean and a net sink for oceanic and atmospheric O 2 . Rates of metabolism were extremely high, with respiration (43 mol m -2 yr -1 ) greatly exceeding gross primary production (28 mol m -2 yr -1 ), such that the overall system was net heterotrophic. Metabolism measured with DIC were higher than with O 2 , which we attribute to high rates of anaerobic respiration and reduced sulfur storage in salt marsh sediments, and we assume substantial levels of anoxygenic photosynthesis. We found gas exchange from a flooded marsh is substantial, accounting for about 28% of total O 2 and CO 2 air-water exchange. A significant percentage of the overall estuarine aquatic metabolism is attributable to metabolism of marsh organisms during inundation. Our study suggests not rely on oceanographic stoichiometry to convert from O 2 to C based measurements when constructing C balances for the coastal ocean. We also suggest eddy covariance measurements of salt marsh net ecosystem exchange underestimate net ecosystem production as they do not account for lateral DIC exchange associated with marsh tidal inundation.

In 1979, Pulsed electromagnetic fields (PEMFs) were approved by the Food and Drug Administration as an effective method in the treatment of non-unions. As well as PEMFs, also static magnetic fields (SMFs) have been widely investigated in orthopaedic studies. Even if the exact mechanism of action is not well understood, a large number of studies showed specific effects both at cellular and tissue levels. As bone fracture healing and osseointegration share the same biological events, the application of magnetic field stimulation in order to facilitate the osseointegration process has been suggested. In this study we investigated BIC and newly formed bone volume around dental implants inserted in the tibia of New Zealand rabbits after SMF stimulation, generated by a small-customized cover-screw-shaped neodymium-iron-bore magnet placed in the inner cavity of dental implants. As a result, we found that the SMF field generated around dental implants enhanced bone healing in the animal model. Our findings represent, to our knowledge, the first ready clinical technique for dental implants showing the ability of SMF to promote the osteogenesis process in vivo.

Aim: To evaluate the growth of Human Gingival Fibroblasts (HGFs) cultured onto sample discs of CAD/CAM zirconia and veneering ceramic for zirconia by means of Scanning Electron Microscope (SEM) analysis at different experimental times., Methods: A total of 26 experimental discs, divided into 2 groups, were used: Group A) CAD/CAM zirconia (3Y-TZP) discs (n=13); Group B) veneering ceramic for zirconia discs (n=13). HGFs were obtained from human gingival biopsies, isolated and placed in culture plates. Subsequently, cells were seeded on experimental discs at 7,5×10(3)/cm(2) concentration and cultured for a total of 7 days. Discs were processed for SEM observation at 3h, 24h, 72h and 7 days., Results: In Group A, after 3h, HGFs were adherent to the surface and showed a flattened profile. The disc surface covered by HGFs resulted to be wider in Group A than in Group B samples. At SEM observation, after 24h and 72h, differences in cell attachment were slightly noticeable between the groups, with an evident flattening of HGFs on both surfaces. All differences between Group A and group B became less significant after 7 days of culture in vitro., Conclusions: SEM analysis of HGFs showed differences in terms of cell adhesion and proliferation, especially in the early hours of culture. Results showed a better adhesion and cell growth in Group A than in Group B, especially up to 72h in vitro. Differences decreased after 7 days, probably because of the rougher surface of CAD/CAM zirconia, promoting better cell adhesion, compared to the smoother surface of veneering ceramic.

The aim of the present research is an in vitro evaluation of the preload distribution in screw-retained implant systems under cyclic load. Two implant systems with internal connection were tested: fifteen 4.5 × 10 mm implants with internal hexagon and fifteen 4.5 × 10 mm implants with internal octagon. Samples underwent cyclic load that was between 20 N and 200 N for 1 × 10(6) cycles. After mechanical tests, samples were sectioned along the long axis and analyzed under a scanning electron microscope. Five 4.5 × 10 mm implants with internal hexagon and five 4.5 × 10 mm implants with internal octagon were collected for photoelastic analysis. Each fixture was mounted in a wax-made parallelepiped measuring 20 mm × 20 mm × 10 mm. A mold was made for each wax parallelepiped/fixture assembly using a silicone-based impression material, and an epoxy resin was poured in each mold. After setting of the resin, 25° angled titanium abutments were screwed onto each replica; afterwards, assemblies underwent photoelastic analysis. After cyclic load, screw threads and heads were still in contact with internal fixture threads and abutment holes, respectively, suggesting that preload has not been lost during load. During load, SSO and Xsigñ implants behave in a different way. SSO samples revealed the presence of fringes radiating from the base of the abutment. Xsigñ implants showed the presence of fringes radiating from the threads of the retention screw. From the present in vitro research, it is possible to state that screw-retained abutment based on an internal octagonal connection is less likely to come loose after cyclic load.

On May 31, 2010, a direct acoustic measurement method was used to quantify fluid leakage rate from the Deepwater Horizon Macondo well prior to removal of its broken riser. This method utilized an acoustic imaging sonar and acoustic Doppler sonar operating onboard a remotely operated vehicle for noncontact measurement of flow cross-section and velocity from the well's two leak sites. Over 2,500 sonar cross-sections and over 85,000 Doppler velocity measurements were recorded during the acquisition process. These data were then applied to turbulent jet and plume flow models to account for entrained water and calculate a combined hydrocarbon flow rate from the two leak sites at seafloor conditions. Based on the chemical composition of end-member samples collected from within the well, this bulk volumetric rate was then normalized to account for contributions from gases and condensates at initial leak source conditions. Results from this investigation indicate that on May 31, 2010, the well's oil flow rate was approximately 0.10 ± 0.017 m(3) s(-1) at seafloor conditions, or approximately 85 ± 15 kg s(-1) (7.4 ± 1.3 Gg d(-1)), equivalent to approximately 57,000 ± 9,800 barrels of oil per day at surface conditions. End-member chemical composition indicates that this oil release rate was accompanied by approximately an additional 24 ± 4.2 kg s(-1) (2.1 ± 0.37 Gg d(-1)) of natural gas (methane through pentanes), yielding a total hydrocarbon release rate of 110 ± 19 kg s(-1) (9.5 ± 1.6 Gg d(-1)).

The recently introduced ultrasonic osteotome procedure is an alternative to conventional rotatory burs. The aim of this study was to establish the differences between two ultrasonic osteotomes and conventional rotatory burs, in order to perform micromorphological and histological analyses of osteotomized bone surfaces. Bony samples were taken from adult bovine ribs including both the cortical and marrow bone. Soft tissues have been removed and the bone pieces were divided into four groups, to test four devices: a conventional osteotomy round bur, a Lindeman bur and piezoelectric osteotomes ES007 and the T-Black. Each device performed cuts that were examined via scanning electron microscope (SEM) and light microscopy (LM) to check respectively cut precision and bone architecture all along the defect borders. SEM analysis of specimens showed that burs created defects of greater width and with irregular edges while those produced by ultrasonic osteotomes were narrow and had mostly smooth cutting surfaces. The edges of incisions made by drills were full of bone fragments while less bone chips were observed on piezoincision’s ones. Dimensions of fragments were wider if cuts were made by burs too. LM analysis of samples showed focally, delicate bony trabecules crushed and pressed into the bone marrow in cutting made by burs. Samples cut by ultrasonic devices showed small or no smear layer and only partial or no crushed trabecules. Osteocytes seemed to be intact all along the cutting surface in all samples observed. In the present study, according to literature, ultrasonic surgery validity is confirmed. As a matter of fact, the greater the number of bone chips products, the greater the magnitude of the inflammatory process induced, as well as the possibility of a greater bone loss and delay in wound healing near the osteotomized area.

Acoustic methods are applied to the investigation and monitoring of a vigorous hydrothermal plume within the Main Endeavor vent field at the Endeavor segment of the Juan de Fuca Ridge. Forward propagation and scattering from suspended particulates using Rayleigh scattering theory is shown to be negligible (log-amplitude variance σ(χ) (2)~10(-7)) compared to turbulence induced by temperature fluctuations (σ(χ) (2)~0.1). The backscattering from turbulence is then quantified using the forward scattering derived turbulence level, which gives a volume backscattering strength of s(V)=6.5 × 10(-8) m(-1). The volume backscattering cross section from particulates can range from s(V)=3.3 × 10(-6) to 7.2 × 10(-10) m(-1) depending on the particle size. These results show that forward scatter acoustic methods in hydrothermal vent applications can be used to quantify turbulence and its effect on backscatter measurements, which can be a dominant factor depending on the particle size and its location within the plume., (© 2011 Acoustical Society of America)

Aim: The aim of this work is to analyze by scanning electron microscopy implant components that have mechanically failed in vivo., Materials and Methods: Three clinical cases are presented relative to single lateral posterior restorations supported by implants and a case of a mandibular overdenture supported by two implants. In all the reported cases the presence of an incongruous occlusal load caused the fracture of the components of the implant supported restorations., Conclusion: From the analysis of the cases examined in this study, it is deduced that the functional overload influences the biomechanical behavior of the prosthetic rehabilitation supported by an implant and may, in less fortunate cases, determine the failure following the fracture of the connecting screws and/or the fixture.

Objectives: This in vitro study evaluated the friction (F) generated by aligned stainless steel (SS) conventional brackets, self-ligating Damon MX(©) brackets (SDS Ormco, Glendora, California, USA), Time3(©) brackets (American Orthodontics, Sheboygan, Wisconsin, USA), Vision LP(©) brackets (American Orthodontics), and low-friction Slide(©) ligatures (Leone, Firenze, Italy) coupled with various SS, nickel-titanium (NiTi), and beta-titanium (TMA) archwires., Methods: All brackets had a 0.022-inch slot, and the orthodontic archwires were 0.014-inch, 0.016-inch, 0.014×0.025-inch, 0.018×0.025-inch, and 0.019×0.025-inch NiTi; 0.017×0.025-inch TMA; and 0.019×0.025-inch SS. Each bracket-archwire combination was tested 10 times. In the test, 10 brackets of the same group were mounted in alignment on a metal bar. The archwires moved through all the 10 brackets at a crosshead speed of 0.5 mm/min (each run lasted approximately 5 min). The differences among 5 groups of brackets were analyzed through the Kruskal-Wallis test, and a Mann-Whitney test was calculated as post hoc analysis. The P value was set at 0.05., Results: Coupled with 0.014-inch NiTi and 0.016-inch NiTi, Victory Series(©) brackets generated the greatest F, while Damon MX(©) and Vision LP(©) brackets generated the lowest (P<.05); no significant differences were observed between Time3(©) brackets and Slide(©) ligatures. Coupled with all the rectangular archwires, Victory Series(©) brackets, Slide(©) ligatures, and Vision LP(©) self-ligating brackets generated significantly lower F than did Time3(©) and Damon MX(©) self-ligating brackets (P<.05)., Conclusions: These findings suggest that self-ligating brackets are a family of brackets that, in vitro, can generate different levels of F when coupled with thin or thick, rectangular, or round archwires. Clinical conclusions based on our results are not possible due to the limitations of the experimental conditions.

Aim: The aim of the present in vitro study is to compare the resistance to fracture under a cyclic load applied to chamfer-edged vs. shoulder-edged Procera All Ceram cores., Materials and Methods: An extracted first maxillary premolar was prepared with a 50 degrees chamfer margin using conventional diamond burs, and an impression was taken using a polyvinylsiloxane. The impression was poured ten times using resin to fabricate dies. The same tooth was retrieved and the 50 degrees chamfer was converted into a 90 degrees shoulder by means of an appropriate diamond bur. An impression was taken and ten more resin dies were fabricated. The resin dies were cast using the lost wax technique in order to obtain brass copies. Impressions of each brass die were taken using a polyvinylsiloxane impression material and poured with die stone. The stone dies were sent to a dental laboratory where densely sintered alumina cores 0.4 mm thick were fabricated using a CAD/CAM process. The alumina cores were then cemented on the brass dies and underwent a fracture test with a cyclic load for 24 hours. Fragments were retrieved for fracture characterization using scanning electron microscopy (SEM)., Results: The mean values of fracture resistance for the chamfer samples were 406.10 +/- 67.271 N and 643.90 +/- 32.912 N for the shoulder samples. The Student's t-test revealed a statistically significant difference between groups., Conclusions: The results of this in vitro study indicate a relationship between the cervical thickness of the alumina cores and their fracture resistance. A shoulder margin could improve the biomechanical performance of posterior single crown alumina restorations.

The friction generated by various bracket-archwire combinations previously has been studied using in vitro testing models that included only one or three brackets. This study was performed using a specially designed apparatus that included 10 aligned brackets to compare the frictional resistance generated by conventional stainless steel brackets, self-ligating Damon SL II brackets and Time Plus brackets coupled with stainless steel, nickel-titanium and beta-titanium archwires. All brackets had a 0.022-inch slot, and five different sizes of orthodontic wire alloys used. Each bracket-archwire combination was tested 10 times, and each test was performed with a new bracket-wire sample. Time Plus self-ligating brackets generated significantly lower friction than both the Damon SL II self-ligating brackets and Victory brackets. However, the analysis of the various bracket-archwire combinations showed that Damon SL II brackets generated significantly lower friction than the other brackets when tested with round wires and significantly higher friction than Time Plus when tested with rectangular archwires. Beta-titanium archwires generated higher frictional resistances than the other archwires. All brackets showed higher frictional forces as the wire size increased. These findings suggest that the use of an in vitro testing model that includes 10 brackets can give additional interesting information about the frictional force of the various bracket-archwires combinations to the clinician and the research worker.

A new dental flowable composite, Denfil Flow, was evaluated for the bonding of orthodontic brackets by determining its shear bond strength (SBS) and the mode of bond failure after debonding. Eighty extracted human premolars were divided into two equal groups. Metal brackets were bonded to etched enamel using a composite resin control (Transbond XT) or Denfil Flow. After 72 hours of incubation in saline solution at 37 degrees C, debonding was performed with a shearing force. The SBS and the mode of bond failure were examined. In addition, representative samples from each group were examined by scanning electron microscopy (SEM). No significant difference was observed in the SBS between the groups, and a clinically acceptable SBS was found for the two adhesives. Bond failures occurred mostly in the bracket-adhesive interface, without significant differences between the groups. At SEM analysis, Denfil Flow showed a greater frequency of air bubbles within the resin than did Transbond XT. In conclusion, Denfil Flow displayed the same SBS as traditional composite resins and similar bond failures. Further clinical studies are required.