Assessment of physical properties of bioactive glass-modified universal multimode adhesive and its bonding potential to artificially induced caries affected dentin

BACKGROUND

To evaluate the physical properties of bioactive glass-modified universal multimode adhesive and its micro-tensile bond strength (µTBS) to artificially induced caries-affected dentin.

METHODS

All bond universal adhesive was used in the study. Specimens were divided into 2 main groups: control unmodified adhesive and 5 wt% BAG modified adhesive. The degree of conversion, pH, bioactivity, and viscosity of the adhesives were tested with n = 5 for each test. Micro-tensile bond strength evaluation was done in etch & rinse (ER) and selective-etch (SE) modes, where 24 human molar teeth were used (n = 3), 12 teeth for immediate bond strength, and the other 12 were tested after 6 months of storage in simulated body fluid (SBF).

RESULTS

No significant difference was found between the control and the 5wt% BAG groups regarding the degree of conversion (61.01 ± 0.43 and 60.44 ± 0.61 respectively) and the viscosity (109.77 ± 22.3 and 124.3 ± 9.92 respectively). The control group revealed significantly lower pH values than the 5wt% BAG group (3.16 ± 0.5 and 4.26 ± 0.09 respectively). Immediate bond strength results revealed that the 5wt% BAG in the ER mode had the highest bond strength followed by the control group in the ER mode (44.16 ± 7.53 and 44.00 ± 7.96 respectively). SE groups showed that the immediate strength of the 5wt% BAG group was higher than the control group (42.09 ± 6.02 and 39.29 ± 6.64 respectively). After 6 months of storage, bond strength results revealed a decrease in bond strength values for the control groups but not for the 5wt% BAG in both application modes.

CONCLUSIONS

The incorporation of BAG (5wt%) improved the universal adhesive micro-tensile bond strength and bond durability for both adhesive application modes without affecting its degree of conversion or viscosity.

Application of laser on enamel surface with three types of bioactive glasses-based resin infiltrants: An in vitro study

OBJECTIVE

The study aimed to evaluate and compare the surface micro-hardness, roughness, color, and morphology of enamel after Er,Cr:YSGG laser irradiation, followed by application of three types of bioactive glasses-based resin infiltrants, and the samples groups were challenged with the pH cycle.

METHODOLOGY

Experimental photoactivated resin infiltrants were synthesized using dimethacrylate resins, whereby three different types of bioactive glasses (BGs), i.e., 45S5, fluoridated-BG (F-BG), and borosilicate-BG (B-BG), were incorporated into the resin system. Initially, white spot lesions were created artificially on the toosth enamel surface, then irradiated with Er,Cr:YSGG laser. Then, the resin-only and BG-based resins were infiltrated on the enamel surface. All samples were pH challenged for 14 days, and the micro-hardness, surface roughness, surface morphology, and color stability (ΔE) analyses were conducted before and after the 14 days pH challenge.

RESULTS

After laser irradiation, the micro-hardness was significantly high with 45S5 group compared to resin-only (p = 0.021), F-BG (p = 0.042), and B-BG (p = 0.001) groups. After the pH challenge, the micro-hardness values for all groups were reduced significantly (p ≤ 0.05). The surface roughness was least with the resin-only group and showed a non-significant difference with F-BG (p = 0.34) and significant differences with both B-BG (p = 0.005), and 45S5 (p = 0.010) groups. After the pH cycle, the roughness of all groups was increased significantly (p ≤ 0.05), except B-BG group showed a non-significant difference (p = 0.528). The B-BG group showed significantly high ΔE between day 0 and baseline compared to resin-only (p = 0.0008), F-BG (p = 0.017), and 45S5 (p = 0.029), whereas between day 14 and baseline, the lowest ΔE value was observed for B-BG (14.2 ± 2.10) and maximum for the resin-only (20.57 ± 2.47) group. The SEM images showed pitting on the surface of all resin infiltrant groups after 14 days of pH challenge.

CONCLUSION

The morphological difference was observed after the laser irradiation on the enamel surface. The differences in micro-hardness, surface roughness, and color were observed after the application of experimental resin infiltrants and significant differences were observed after the pH challenge.

Bioactive Inorganic Materials for Dental Applications: A Narrative Review

Over time, much attention has been given to the use of bioceramics for biomedical applications; however, the recent trend has been gaining traction to apply these materials for dental restorations. The bioceramics (mainly bioactive) are exceptionally biocompatible and possess excellent bioactive and biological properties due to their similar chemical composition to human hard tissues. However, concern has been noticed related to their mechanical properties. All dental materials based on bioactive materials must be biocompatible, long-lasting, mechanically strong enough to bear the masticatory and functional load, wear-resistant, easily manipulated, and implanted. This review article presents the basic structure, properties, and dental applications of different bioactive materials i.e., amorphous calcium phosphate, hydroxyapatite, tri-calcium phosphate, mono-calcium phosphate, calcium silicate, and bioactive glass. The advantageous properties and limitations of these materials are also discussed. In the end, future directions and proposals are given to improve the physical and mechanical properties of bioactive materials-based dental materials.

Development and Characterization of Zein/Ag-Sr Doped Mesoporous Bioactive Glass Nanoparticles Coatings for Biomedical Applications

Implants are used to replace damaged biological structures in human body. Although stainless steel (SS) is a well-known implant material, corrosion of SS implants leads to the release of toxic metallic ions, which produce harmful effects in human body. To prevent material degradation and its harmful repercussions, these implanted materials are subjected to biocompatible coatings. Polymeric coatings play a vital role in enhancing the mechanical and biological integrity of the implanted devices. Zein is a natural protein extracted from corn and is known to have good biocompatibility and biodegradability. In this study, zein/Ag-Sr doped mesoporous bioactive glass nanoparticles (Ag-Sr MBGNs) were deposited on SS substrates via electrophoretic deposition (EPD) at different parameters. Ag and Sr ions were added to impart antibacterial and osteogenic properties to the coatings, respectively. In order to examine the surface morphology of coatings, optical microscopy and scanning electron microscopy (SEM) were performed. To analyze mechanical strength, a pencil scratch test, bend test, and corrosion and wear tests were conducted on zein/Ag-Sr doped MBGN coatings. The results show good adhesion strength, wettability, corrosion, and wear resistance for zein/Ag-Sr doped MBGN coatings as compared to bare SS substrate. Thus, good mechanical and biological properties were observed for zein/Ag-Sr doped MBGN coatings. Results suggested these zein/Ag-Sr MBGNs coatings have great potential in bone regeneration applications.

Ceramic Stereolithography of Bioactive Glasses: Influence of Resin Composition on Curing Behavior and Green Body Properties

Herein we report on the preparation of a bioactive glass (BAG)-based photocurable resin for the additive manufacturing of BAG scaffolds with high filler loadings. The preparation of glass/ceramics resins for stereolithography with high filler loading is always a challenge, especially for fillers with a high refractive index variance. Various photocurable resin compositions with and without bioactive glass fillers have been investigated to see the influence of bioactive glass on physical properties of the resin and resulting green body. The effect of concentration of monomers, reactive diluent, light absorber (Sudan orange G dye), photoinitiator (PI), non-reactive diluent, and fillers (BAG) on rheology and photocuring behavior of the resin and tomography of the resulting 3D structures have been investigated. The BAG contents affect the rheology of resin and influence the rate of the polymerization reaction. The resin compositions with 55–60% BAG, 10% PEG-200 (diluent), 1% of PI and 0.015% of the dye were found to be suitable compositions for the stereolithographic fabrication. A higher percentage of PI caused over-curing, while a higher amount of dye decreased the cure depth of the resin. The micro-computed tomography (µ-CT) and scanning electron microscopic (SEM) images of the resulting green bodies display a relatively dense glass scaffold without any visible cracks and good interlayer connection and surface finishing. These properties play an important role in the mechanical behavior of 3D scaffolds. This study will be helpful to prepare high density glass/ceramic slurries and optimize their printing properties.

Multifunctional Protein-Decorated Bioactive Glass Nanoparticles for Tumor-Specific Therapy and Bioimaging In Vitro and In Vivo

Multifunctional nanocarriers with a simple structure and biocompatibility for bioimaging, potential tumor targeting, and precise antitumor ability are promising in cancer therapy. Bioactive glass is an important biomaterial and has been used in clinical bone tissue repair due to the high biocompatibility and bioactivity. Herein, we report fetal bovine serum (FBS)-decorated europium-doped bioactive glass nanoparticles (EuBGN@FBS) with excellent biosafety and enhanced tumor targeting for cancer imaging and therapy. EuBGN@FBS showed the controlled photoluminescent properties and pH-responsive anticancer drug release behavior. The FBS decoration significantly enhanced the dispersibility in physiological medium and improved hemocompatibility and cellular uptake of EuBGN. Relative to EuBGN, EuBGN@FBS could also efficiently image the cancer cell and show significantly enhanced targeted tumor imaging and chemotherapy in vivo while retaining negligible side effects. The simple and biocompatible structure with efficient tumor targeting, imaging, and therapy makes EuBGN@FBS highly promising in future cancer therapy.

Biological analysis of an innovative biodegradable antibiotic eluting bioactive glass/gypsum composite bone cement for treating experimental chronic MRSA osteomyelitis

A multi-barrier antibiotics loaded biodegradable composite bone cement for resolving chronic osteomyelitis has been studied to understand the physico-mechanical properties, drug loading/eluting efficiency, and different merits and demerits prior to clinical application. After successful induction of bone infection in 28 rabbits using methicillin-resistant Staphylococcus aureus (MRSA) strains, calcium sulfate/bioactive glass based composite cement was implanted in 12 defects to assess its performance over parenteral therapy with microscopic and radiological examination for 90 days. The composite cement revealed acceptable physico-mechanical properties and controlled drug elution kinetics. Furthermore, the antibiotics concentrations in bone up to 42 days were sufficient to kill MRSA without eliciting adverse drug reactions. The striking feature of platelets aggregation by composite cement could assist bone healing. The controlled degradation with simultaneous entrapment of composite cement within the osteoid tissues and complete repair of infected cortical defects (holes) in rabbit tibia at 6 weeks indicated the excellent anti-infective and osteoconductive properties of composite cement. Thus, the animal study demonstrated the superiority of composite over injectable antibiotic therapy based on infection resolution and bone regeneration. We thereby conclude that the composite cement can be effectively applied in the treatment of resistant cases of chronic osteomyelitis.

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Described the preparation method of multi-barrier CS/BG composite bone cement.

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Made by coating the antibiotics loaded porous BG granules with PLGA and α-CSH.

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Introduced antibiotics elution study in ideal immersion medium.

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Beneficial role of PLGA on drug release and activation of platelets by cement was explored.

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New cement showed great potential to repair bone infection and to hasten osteosynthesis.

Bioactivity in SBF versus trace element effects: The isolated role of Mg2+ and Zn2+ in osteoblast behavior

The bioactivity assay originally proposed by Kokubo is one of the most commonly used tests to indirectly evaluate the biocompatibility of bioactive glasses. However, extensive evidence has shown that trace elements present in biomaterials may stimulate cellular behavior in different ways even when no apatite formation is observed, i.e., in biomaterials with low or no bioactivity. To further elucidate this topic, we designed three different SiO₂-rich bioglass compositions in which CaO was partially replaced by ZnO and MgO, two oxides known to affect bioactivity as well as osteoblastic behavior. The physicochemical changes induced by the presence of oxides and their effects on biological behavior, as well as the adhesion, proliferation and differentiation of human osteoblast-like osteosarcoma cells (MG-63), were followed by a bioactivity assay in simulated body fluid (SBF). The insertion of ZnO or MgO decreased the glass transition (T_g) and crystallization (T_c) temperatures as a function of the increase in nonbonding oxygens, which was directly reflected in the higher solubility. The release of Mg²⁺ ions from the MgO-containing samples inhibited the bioactivity in SBF, inducing high cell adhesion and proliferation and moderate ALP activity. The release of Zn²⁺ also inhibited the bioactivity in SBF but, in contrast to the release of Mg²⁺, induced low cell adhesion and proliferation and high ALP activity compared to the control.

Smart injectable self-setting bioceramics for dental applications

A thermo-responsive injectable bioactive glass (BAG) that has the ability to set at body temperature was prepared using pluronic F127 and hydroxypropyl methylcellulose as the carrier. The injectable composite has the advantage to fill irregular shape implantation sites and quick setting at body temperature. The structural and morphological analysis of injectable BAG before and after setting was done by using Fourier Transform Infrared spectroscopy (FTIR), and Scanning Electron Microscope (SEM). The effect of an ultrasonic scaler for a quick setting of injectable BAG was also investigated. The ultrasonic scaler sets the BAG formulation three-folds faster than at body temperature and homogenized the dispersion. The in vitro bio-adhesion was studied in the bovine tooth in both artificial saliva and deionized water for periodic time intervals, i.e., day 7, 30, 90, and 180, which confirmed the apatite layer formation. The mineral density analysis was used to differentiate the newly formed apatite with tooth apatite. In the MTT assay, the experimental material showed continuous proliferation and cell growth. This indicated that injectable hydrogel promoted cell growth, facilitated proliferation, and had no cytotoxic effect. The SEM and micro-CT results (performed after in vitro bioactivity testing) showed that the injectable BAG had the ability to regenerate dentin, hence this material has the potential to be used for dental and biomedical applications including tooth and bone regeneration in minimally invasive procedures in future.

Glassy dynamics in asymmetric binary mixtures of hard spheres

We perform a systematic and detailed study of the glass transition in highly asymmetric binary mixtures of colloidal hard spheres, combining differential dynamic microscopy experiments, event-driven molecular dynamics simulations, and theoretical calculations, exploring the whole state diagram and determining the self-dynamics and collective dynamics of both species. Two distinct glassy states involving different dynamical arrest transitions are consistently described, namely, a double glass with the simultaneous arrest of the self-dynamics and collective dynamics of both species, and a single glass of large particles in which the self-dynamics of the small species remains ergodic. In the single-glass scenario, spatial modulations in the collective dynamics of both species occur due to the structure of the large spheres, a feature not observed in the double-glass domain. The theoretical results, obtained within the self-consistent generalized Langevin equation formalism, are in agreement with both simulations and experimental data, thus providing a stringent validation of this theoretical framework in the description of dynamical arrest in highly asymmetric mixtures. Our findings are summarized in a state diagram that classifies the various amorphous states of highly asymmetric mixtures by their dynamical arrest mechanisms.

Fabrication, in vitro and in vivo studies of bilayer composite membrane for periodontal guided tissue regeneration

Development of a guided occlusive biodegradable membrane with controlled morphology in order to restrict the ingrowth of epithelial cells is still a challenge in dental tissue engineering. A bilayer membrane with a non-porous upper layer (polyurethane) and porous lower layer (polycaprolactone and bioactive glass composite) with thermoelastic properties to sustain surgery treatment was developed by lyophilization. Morphology, porosity, and layers attachment were controlled by using the multi-solvent system. In vitro and in vivo biocompatibility, cell attachment, and cell proliferation were analyzed by immunohistochemistry and histology. The cell proliferation rate and cell attachment results showed good biocompatibility of both surfaces, though cell metabolic activity was better on the polycaprolactone-bioactive glass surface. Furthermore, the cells were viable, adhered, and proliferated well on the lower porous bioactive surface, while non-porous polyurethane surface demonstrated low cell attachment, which was deliberately designed and a pre-requisite for guided tissue regeneration/guided bone regeneration membranes. In addition, in vivo studies performed in a rat model for six weeks revealed good compatibility of membranes. Histological analysis (staining with hematoxylin and eosin) indicated no signs of inflammation or accumulation of host immune cells. These results suggested that the fabricated biocompatible bilayer membrane has the potential for use in periodontal tissue regeneration.

Tailoring the subchondral bone phase of a multi-layered osteochondral construct to support bone healing and a cartilage analog

Focal chondral and osteochondral defects create significant pain and disability for working-aged adults. Current osteochondral repair grafts are limited in availability and often fail due to insufficient osseous support and integration. Thus, a need exists for an off-the-shelf osteochondral construct with the propensity to overcome these shortcomings. Herein, a scalable process was used to develop a multi-layered osteochondral graft with a subchondral bone (ScB) phase tailored to support bone healing and integration. Multiple ScB formulations and fabrication techniques were screened via degradation, bioactivity, and unconfined compression testing. An optimized ScB construct was selected and its cytotoxicity assessed. Additionally, a cartilage analog was secured to the optimized ScB construct via a calcified cartilage layer, and the resulting osteochondral construct was characterized via interfacial shear and dynamic mechanical testing. The optimized ScB construct did not significantly alter local pH during degradation, exhibited measurable bioactivity in vitro, and had significantly greater compressive mechanical strength compared to other constructs. The attachment strength of the cartilage analog was significantly greater by an increase in compressive dynamic mechanical properties. Furthermore, this ScB construct was found to be cytocompatible with human bone marrow-derived mesenchymal stromal cells. Taken together, this optimized ScB material forms the robust foundation of a novel, off-the-shelf osteochondral construct to be used in defect repair.

STATEMENT OF SIGNIFICANCE

The quality of life for millions of individuals worldwide is detrimentally affected by focal chondral or osteochondral defects. Current off-the-shelf biomaterial constructs often fail to repair these defects due to insufficient osseous support and integration. Herein, we used a scalable process to fabricate and optimize a novel boney construct. This optimized boney construct demonstrated biochemical, physical, and mechanical properties tailored to promote bone healing. Furthermore, a novel cartilage analog was successfully attached to the boney construct, forming a multi-layered osteochondral construct.

Microwave-assisted synthesis and evaluation of type 1 collagen-apatite composites for dental tissue regeneration

The aim was to develop an economical and biocompatible collagen-based bioactive composite for tooth regeneration. Acid-soluble collagen was extracted and purified from fish scales. The design was innovated to molecularly tailor the surface charge sites of the nano-apatite providing chemical bonds with the collagen matrix via microwave irradiation technique. The obtained collagen was identified by sodium dodecyl sulfate polyacrylamide gel electrophoresis analysis. The composites were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis/differential scanning calorimetry, and scanning electron microscopy. MC3T3-E1 cell lines were used to assess the biological effects of these materials by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl-tetra zolium bromide (MTT) assay. Indirect contact test was performed by extracting representative elutes in cell culture media and sulforhodamine B analysis was performed. Chorioallantoic membrane assay was conducted to define the new vessels formation behavior. The purity of collagen extracts was determined and showed two α-chains, i.e. the characteristic of type I collagen. Fourier transform infrared spectroscopy showed the characteristic peaks for amide I, I, III, and phosphate for collagen and composites. Scanning electron microscopy images showed three-dimensional mesh of collagen/apatite nano-fibers. Nontoxic behavior of composites was observed and there were graded and dose-related effects on experimental compounds. The angiogenesis and vessels formation behavior were observed in bioactive collagen composite. The obtained composites have potential to be used for tooth structure regeneration.

Vacuumed collagen-impregnated bioglass scaffolds: Characterization and influence on proliferation and differentiation of bone marrow stromal cells

This study evaluated physical-chemical characteristics of a vacuumed collagen-impregnated bioglass (BG) scaffolds and bone marrow stromal cells (BMSCs) behavior on those composites. scanning electron microscope and energy dispersive x-ray spectroscope demonstrated collagen (Col) was successfully introduced into BG. Vacuum impregnation system has showed efficiency for Col impregnation in BG scaffolds (approximately 20 wt %). Furthermore, mass weight decreasing and more stabilized pH were observed over time for BG/Col upon incubation in phosphate buffered saline compared to plain BG under same conditions. Calcium evaluation (Ca assay) demonstrated higher calcium uptake for BG/Col samples compared to BG. In addition, BG samples presented hydroxyapatite crystals formation on its surface after 14 days in simulated body fluid solution, and signs of initial degradation were observed for BG and BG/Col after 21 days. Fourier transform infrared spectroscopy spectra for both groups indicated peaks for hydroxyapatite formation. Finally, a significant increase of BMSCs viability for both composites was observed compared to control group, but no increase of osteogenic differentiation-related gene expressions were found. In summary, BG/Col scaffolds have improved degradation, pH equilibrium and Ca mineralization over time, accompanied by hydroxyapatite formation. Moreover, both BG and BG/Col scaffolds were biocompatible and noncytotoxic, promoting a higher cell viability compared to control. Future investigations should focus on additional molecular and in vivo studies in order to evaluate biomaterial performance for bone tissue engineering applications. © 2018 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 107B: 211-222, 2019.

Physicochemical properties and biocompatibility of PZL/PLGA/bioglass composite scaffolds for bone tissue engineering

Foamy poly(N_ε-Cbz-l-lysine)/poly(lactic-co-glycolic acid)/bioglass composite scaffolds had appropriate physicochemical properties, good biomineralization ability, excellent cytocompatibility and histocompatibility, and desirable osteogenic ability.