Glass microparticle‐ versus microsphere‐filled experimental dental adhesives

This study aimed to formulate antibacterial dental adhesives. Phosphate‐substituted methacrylate adhesives were modified with 0–20 wt % copper‐doped glass microparticles. Two shapes of microparticles were used: regular shaped (microspheres) and irregular shaped (microparticles). The morphology/composition, roughness, monomer conversion (DC%), thermogravimetric analysis, and antibacterial action against S. mutans and P. aeruginosa and ion release were investigated. The results showed that microspheres produced adhesives with a relatively smoother surface than microparticles did. The DC% of adhesives increased with increasing glass filler content. Filled adhesives showed polymer decomposition at ~315 °C and glass melting at 600–1000 °C. The weight loss percent of adhesives decreased with increasing weight percent of fillers. Glass microparticles at 0–20 wt % significantly increased the antibacterial action of adhesives against both bacteria. Glass microspheres at 0–5 wt % significantly increased the antibacterial action of adhesives against both bacteria. Only 20 wt % microparticle‐filled adhesive showed an inhibition zone similar to tobramycin (positive control). Microparticle‐filled adhesives (with >5 wt % filler) significantly reduced S. mutans more than their microsphere counterparts. Microsphere‐filled adhesives (with ≤5 wt % filler) significantly reduced P. aeruginosa more than their microparticle counterparts. Microsphere‐filled adhesives showed higher Cu release than their microparticle counterparts. Accordingly, phosphate‐substituted methacrylate filled with glass could be used as an antibacterial adhesive

Glass microparticle‐ versus microsphere‐filled experimental dental adhesives

This study aimed to formulate antibacterial dental adhesives. Phosphate‐substituted methacrylate adhesives were modified with 0–20 wt % copper‐doped glass microparticles. Two shapes of microparticles were used: regular shaped (microspheres) and irregular shaped (microparticles). The morphology/composition, roughness, monomer conversion (DC%), thermogravimetric analysis, and antibacterial action against S. mutans and P. aeruginosa and ion release were investigated. The results showed that microspheres produced adhesives with a relatively smoother surface than microparticles did. The DC% of adhesives increased with increasing glass filler content. Filled adhesives showed polymer decomposition at ~315 °C and glass melting at 600–1000 °C. The weight loss percent of adhesives decreased with increasing weight percent of fillers. Glass microparticles at 0–20 wt % significantly increased the antibacterial action of adhesives against both bacteria. Glass microspheres at 0–5 wt % significantly increased the antibacterial action of adhesives against both bacteria. Only 20 wt % microparticle‐filled adhesive showed an inhibition zone similar to tobramycin (positive control). Microparticle‐filled adhesives (with >5 wt % filler) significantly reduced S. mutans more than their microsphere counterparts. Microsphere‐filled adhesives (with ≤5 wt % filler) significantly reduced P. aeruginosa more than their microparticle counterparts. Microsphere‐filled adhesives showed higher Cu release than their microparticle counterparts. Accordingly, phosphate‐substituted methacrylate filled with glass could be used as an antibacterial adhesive

Antibacterial, Remineralising and Matrix Metalloproteinase Inhibiting Scandium-doped Phosphate Glasses for Treatment of Dental Caries

Objectives: Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions. Methods: Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated. Results: The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log10 CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats. Significance: Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria

Novel lactoferrin-conjugated gallium complex to treat Pseudomonas aeruginosa wound infection

Pseudomonas aeruginosa is one of the leading causes of opportunistic infections such as chronic wound infection that could lead to multiple organ failure and death. Gallium (Ga3+) ions are known to inhibit P. aeruginosa growth and biofilm formation but require carrier for localized controlled delivery. Lactoferrin (LTf), a two-lobed protein, can deliver Ga3+ at sites of infection. This study aimed to develop a Ga-LTf complex for the treatment of wound infection. The characterisation of the Ga-LTf complex was conducted using differential scanning calorimetry (DSC), Infra-Red (FTIR) and Inductive Coupled Plasma Optical Emission Spectrometry (ICP-OES). The antibacterial activity was assessed by agar disc diffusion, liquid broth and biofilm inhibition assays using the colony forming units (CFUs). The healing capacity and biocompatibility were evaluated using a P.aeruginosa infected wound in a rat model. DSC analyses showed thermal transition consistent with apo-lactoferrin; FTIR confirmed the complexation of gallium to lactoferrin. ICP-OES confirmed the controlled local delivery of Ga3+. Ga-LTf showed a 0.57 log10 CFUs reduction at 24 h compared with untreated control in planktonic liquid broth assay. Ga-LTf showed the highest antibiofilm activity with a 2.24 log10 CFUs reduction at 24 h. Furthermore, Ga-LTf complex is biocompatible without any adverse effect on brain, kidney, liver and spleen of rats tested in this study. Ga-LTf can be potentially promising novel therapeutic agent to treat pathogenic bacterial infections

Development of remineralizing, antibacterial dental materials

Light curable methacrylate dental monomers containing reactive calcium phosphate filler (monocalcium phosphate monohydrate (MCPM) with particle diameter of 29 or 90 mu m) and beta-tricalcium phosphate (beta-TCP) at 1: 1 weight ratio in a powder:liquid ratio (PLR) of 1:1 or 3:1 and chlorhexidine diacetate (0 or 5 wt.%), were investigated. Upon light exposure, approximately 90% monomer conversion was gained irrespective of the formulation. Increasing the PLR promoted water sorption by the set material, induced expansion and enhanced calcium, phosphate and chlorhexidine release. Concomitantly, a decline in compressive and biaxial flexural strengths occurred. With a reduction in MCPM particle diameter, however, calcium and phosphate release was reduced and less deterioration in strength observed. After 24 h, the remaining MCPM had reacted with water and beta-TCP, forming, within the set materials, brushite of lower solubility. This provided a novel means to control water sorption, component release and strength properties. Measurable chlorhexidine release was observed for 6 weeks. Both diffusion rate and total percentage of chlorhexidine release decreased with lowering PLR or by adding buffer to the storage solutions. Higher chlorhexidine release was associated with reduced bacterial growth on agar plates and in a biofilm, fermenter. In cell growth media, brushite and hydroxyapatite crystals precipitated on the composite material surfaces. Cells spread on both these crystals and the exposed polymer composite surfaces, indicating their cell compatibility. These formulations could be suitable antibacterial, biocompatible and remineralizing dental adhesives/liners. (C) 2009 Published by Elsevier Ltd. on behalf of Acta Materialia. Inc

Doping of a high calcium oxide metaphosphate glass with titanium dioxide

This study investigates the effect of doping a high calcium oxide containing metaphosphate glass series (CaO)(40)(Na2O)(10)(P2O5)(50) with TiO2 (1, 3, and 5 mol%). TiO2 incorporation increased the density and glass transition temperature while reduced the degradation rate (5 mol% in particular) by twofold compared with (CaO)30 system reported previously. This has been confirmed by ion release and the minimal pH changes. TiP2O7, NaCa(PO3)(3) and CaP2O6 phases were detected for all TiO2-containing ceramics. XPS showed that the surface is composed of Ca, h, and Ti. Ti was recognized mainly as TiO2, but its total amount was lower than theoretical values. P-31 magic angle spinning (MAS) NMR showed a downfield shift of the P-31 lineshape with increasing TiO2, interpreted as an effect of the titanium cation rather than an increase in the phosphate network connectivity. FTIR showed that incorporation of TiO2 increased the strength of the phosphate chains, and the O/P ratio while introducing more Q(1) units into the structure at the expense of the Q(2) units. There were no differences, however, in surface topography roughness and free energies between these glasses. These results suggested that TiO2 and CaO were acting synergistically in producing glasses with controllable bulk and structural propertie

Bioactive functional materials: a perspective on phosphate-based glasses

The general trend in biomaterials is to use and employ materials that play an active role in tissue regeneration rather than passive and inert materials. Therefore, understanding how a material interacts with the surrounding environments, including cells and tissue fluid, allows material design to be tailored so that implants can be constructed to promote a specific biological response, helping them better perform their function. This class of materials has been described as the "Third Generation" of biomaterials. Phosphate based glasses fall into this category and it has been shown that the properties of these glasses can be tuned via their composition according to the desired end application. These glasses can be prepared as melt-quenched or sol-gel bulk form suitable for potential hard tissue engineering applications and as vehicles for antimicrobial agents. They can also be prepared as fibres suitable for soft tissue engineering applications such as those involving muscle, ligaments, and tendon, where, like the fibres, the tissue has a high degree of anisotropy

Macrofauna along the Sudanese Red Sea coast: potential effect of mangrove clearance on community and trophic structure

Mangroves along the Sudanese Red Sea coast are under constant anthropogenic pressure. To better understand the influence of mangrove clearance on the intertidal benthic community, we investigated the composition, biodiversity and standing stock of the macrofauna communities at high-, mid- and low-water levels in three contrasting habitats: a bare sand flat, a cleared mangrove and an intact mangrove. In addition, a community-wide metric approach based on taxon-specific carbon and nitrogen isotope values was used to compare the trophic structure between the three habitats. The habitats differed significantly in terms of macrofaunal standing stock, community composition and trophic structure. The high- and mid-water levels of the intact mangroves showed a distinct macrofaunal community characterized by elevated densities and biomass, largely governed by higher decapod and gastropod abundances. Diversity was similar for cleared and intact mangroves, but much lower for the bare sand flat. Community-wide metrics indicated highest trophic diversity and community niche breadth in the intact mangroves. Differences between the cleared and intact mangroves can be partly attributed to differences in sediment characteristics resulting from mangrove clearance. These results suggest a significant impact of mangrove clearance on the macrofaunal community and trophic structure. This study calls for further investigations and management actions to protect and restore these habitats, and ensure the survival of this ecologically valuable coastal ecosystem

Antibacterial effect of titanium dioxide-doped phosphate glass microspheres filled total-etch dental adhesive on S. mutans biofilm

Purposeto improve the antibacterial action of a two-step total-etch dental adhesive by using titanium dioxide-doped phosphate glass microspheres (GMs) without affecting its penetration ability.Materials and MethodsFive and 10 wt% of APTES silanized [surface treated with 3-Aminopropyltriethoxysilane (APTES)] and non-silanized GMs have been used as a filler to AdperTM Single Bond 2 Refill. The morphology, chemistry and ζ - potential of GMs have been investigated using scanning electron microscopy, Fourier transform infra-red (FTIR) spectroscopy and Zeta-sizer respectively. The chemistry and antibacterial action of filled adhesive have been investigated using FTIR and nitrocellulose filter membranes (NFM) S. mutans biofilm model respectively. The number of colony forming units (CFU) per NFM was considered. The contact angle and microtensile bond strength of adhesives to mid-coronal dentin, as a measure of its penetration ability, have been investigated using a Drop Shape Analyzer and microtensile testing machine respectively. AdperTM Single Bond 2 Refill was used as a control.ResultsThe size of GMs varied from 60-200 μm. The silanization process was confirmed by reduction in ζ-potential [-7 (±2) mV] and the presence of amide (1500-1600 cm-1), C-N (1380 cm-1), Si-O-Si (1096 cm-1) and Si-O-C (780 cm-1) peaks. Incorporation of GMs had no adverse effect on monomer conversion. All tested adhesives including the control showed significantly higher antibacterial action (∼5-7 log10 reduction in CFU) than the NFM control. All filled adhesives showed significantly higher antibacterial action (∼1-2 log10 reduction in CFU) than the control adhesive. The non-silanized GMs filled adhesives showed the highest antibacterial action against S. mutans biofilm formation. The presence of silanized GMs did not affect the wetting but increased the microtensile bond strength of the adhesive to dentin.ConclusionGlass microsphere modified adhesives could be promising to reduce the possibility of recurrent caries around restorations

Antibacterial, Remineralizing Zinc Oxide-Doped Phosphate-Based Glasses

This study reports a novel melt quenched zinc oxide-doped phosphate-based glasses (Zn-PBGs) of varying CaO mol% designated as C11, C12, C13. The glass degradation rate, ions release, antibacterial activity against S. mutans and remineralization potential were investigated. Zn-PBGs showed one order of magnitude higher degradation rate than Zn-free PBG. The highest rate was observed for C11; Na+, Ca2+, Zn2+ and P5+ release followed the same trend. The higher the Zn2+ release, the greater the S. mutans growth inhibition. C11 showed significantly lower mineral loss from enamel than positive and negative controls. Zn-PBGs could be used to reverse enamel demineralization