Bioactivity, cytocompatibility and thermal properties of experimental Bioglass-reinforced composites as potential root-canal filling materials

A better roadmap for designing novel bioactive glasses: effective approaches for the development of innovative revolutionary bioglasses for future biomedical applications

The introduction of bioactive glasses (BGs) precipitated a paradigm shift in the medical industry and opened the path for the development of contemporary regenerative medicine driven by biomaterials. This composition can bond to live bone and can induce osteogenesis by the release of physiologically active ions. 45S5 BG products have been transplanted effectively into millions of patients around the world, primarily to repair bone and dental defects. Over the years, many other BG compositions have been introduced as innovative biomaterials for repairing soft tissue and delivering drugs. When research first started, many of the accomplishments that have been made today were unimaginable. It appears that the true capacity of BGs has not yet been realized. Because of this, research involving BGs is extremely fascinating. However, to be successful, it requires interdisciplinary cooperation between physicians, glass chemists, and bioengineers. The present paper gives a picture of the existing clinical uses of BGs and illustrates key difficulties deserving to be faced in the future. The challenges range from the potential for BGs to be used in a wide variety of applications. We have high hopes that this paper will be of use to both novice researchers, who are just beginning their journey into the world of BGs, as well as seasoned scientists, in that it will promote conversation regarding potential additional investigation and lead to the discovery of innovative medical applications for BGs.

UV-Cured Bio-Based Acrylated Soybean Oil Scaffold Reinforced with Bioactive Glasses

In this study, a bio-based acrylate resin derived from soybean oil was used in combination with a reactive diluent, isobornyl acrylate, to synthetize a composite scaffold reinforced with bioactive glass particles. The formulation contained acrylated epoxidized soybean oil (AESO), isobornyl acrylate (IBOA), a photo-initiator (Irgacure 819) and a bioactive glass particle. The resin showed high reactivity towards radical photopolymerisation, and the presence of the bioactive glass did not significantly affect the photocuring process. The 3D-printed samples showed different properties from the mould-polymerised samples. The glass transition temperature Tg showed an increase of 3D samples with increasing bioactive glass content, attributed to the layer-by-layer curing process that resulted in improved interaction between the bioactive glass and the polymer matrix. Scanning electron microscope analysis revealed an optimal distribution on bioactive glass within the samples. Compression tests indicated that the 3D-printed sample exhibited higher modulus compared to mould-synthetized samples, proving the enhanced mechanical behaviour of 3D-printed scaffolds. The cytocompatibility and biocompatibility of the samples were evaluated using human bone marrow mesenchymal stem cells (bMSCs). The metabolic activity and attachment of cells on the samples' surfaces were analysed, and the results demonstrated higher metabolic activity and increased cell attachment on the surfaces containing higher bioactive glass content. The viability of the cells was further confirmed through live/dead staining and reseeding experiments. Overall, this study presents a novel approach for fabricating bioactive glass reinforced scaffolds using 3D printing technology, offering potential applications in tissue engineering.

Resin-modified glass ionomer enriched with BIOGLASS: Ion-release, bioactivity and antibacterial effect

Developing dental materials for the prevention of remineralization or demineralization is important for high-risk caries patients. This study aimed to evaluate the physicochemical and microbiological effects of adding 45S5 bioglass to resin-modified glass ionomer cement (RMGIC). Samples belonged to the following groups: GIC: conventional glass ionomer cement (Vitro Fil), RMGIC: resin-modified GIC (Vitro Fil LC), and RMGIC/45S5: RMGIC with 10% (wt %) of 45S5. Changes in pH and release of fluoride, calcium, and phosphorus ions under acidic (pH 4) and neutral (pH 7) pH conditions were evaluated. Antibacterial activity was verified based on colony-forming units. Material sorption and solubility were analyzed after bacterial exposure. After 28 days, the bioactivity of the materials was evaluated using scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDS). Analysis of variance, post hoc Scheffe, and Tukey (α = 0.05) tests were employed for statistical analysis. RMGIC/45S5 showed higher alkalization activity, calcium release at pH 4 and 7, and sorption than GIC and RMGIC (p < .05). Release of phosphorus and fluoride at pH 4 and 7 was higher for GIC than that for RMGIC and RMGIC/45S5 (p < .05). RMGIC/45S5 showed higher values than RMGIC (p < .05). However, antibacterial activity did not differ among the groups. Precipitates of calcium and phosphorus were visualized in RMGIC/45S5 samples via SEM/EDS. These results indicate that the RMGIC/45S5 promotes alkalization and increases the release of calcium, phosphorus, and fluoride ions, resulting in precipitate deposition rich in calcium and phosphorus, thereby being a promising option to improve the bioactivity of RMGIC.

Enhanced effect of a novel bioactive glass-ceramic for dental application

OBJECTIVES

Dental caries is the most common chronic disease in humans, caused by the acid produced by the microflora in the mouth that dissolves the enamel minerals. Bioactive glass (BAG) has been used in various clinical applications due to its unique bioactive properties, such as bone graft substitutes and dental restorative composites. In this study, we introduce a novel bioactive glass-ceramic (NBGC) prepared through a sol-gel process under a water-free condition.

MATERIALS AND METHODS

The anti-demineralization and remineralization effects of NBGC were evaluated by comparing the measurements of bovine enamel surface morphology, surface roughness, surface micro-hardness, enamel elements, and mineral content before and after related treatments with a commercial BAG. The antibacterial effect was characterized by minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC).

RESULTS

Results showed that NBGC had greater acid resistance and remineralization potential compared to commercial BAG. The fast formation of a hydroxy carbonate apatite (HCA) layer suggests efficient bioactivity.

CLINICAL RELEVANCE

In addition to its antibacterial properties, NBGC shows promise as an ingredient in oral care products that can prevent demineralization and restore enamel.

Effect of Bioactive Filler Addition on the Mechanical and Biological Properties of Resin-Modified Glass Ionomer

The maintenance of affected dentin can promote the greater conservation of tooth structure. The development of materials that have properties capable of reducing the demineralizing potential and/or even helping in dental remineralization is important for conservative dentistry. This study aimed to evaluate, in vitro, the alkalizing potential, fluoride as well as calcium ion release ability, antimicrobial activity, and dentin remineralization properties of resin-modified glass ionomer cement (RMGIC) incorporated with a bioactive filler (niobium phosphate (NbG) and bioglass (45S5)). The study samples were grouped into RMGIC, NbG, and 45S5. The materials' alkalizing potential, ability to release calcium as well as fluoride ions, and antimicrobial properties concerning Streptococcus mutans UA159 biofilms were analyzed. The remineralization potential was evaluated using the Knoop microhardness test, which was performed at different depths. The alkalizing and fluoride release potential was higher for the 45S5 group (p < 0.001) over time. An increase in the microhardness of demineralized dentin was observed in the 45S5 and NbG groups (p < 0.001). No differences in biofilm formation were observed between the bioactive materials, although 45S5 exhibited lower biofilm acidogenicity at different time points (p < 0.001) and greater calcium ion release in the microbial environment. A resin-modified glass ionomer cement enriched with bioactive glasses, particularly 45S5, is a promising alternative for the treatment of demineralized dentin.

Can strontium replace calcium in bioactive materials for dental applications?

The substitution of calcium with strontium in bioactive materials has been promising but there has been some concern over the material instability and possible toxicity. The aim of this research was the synthesis and characterization of calcium and strontium substituted bioactive materials and assessment of interactions with local tissues and peripheral elemental migration in an animal model. A bioactive glass, hydroxyapatite and hydraulic calcium silicate with 50% or 100% calcium substitution with strontium were developed and the set materials were characterized immediately after setting and after 30 and 180-days in solution. Following subcutaneous implantation, the local (tissue histology, elemental migration) and systemic effects (elemental deposition after organ digestion) were assessed. The strontium-replaced silicate cements resulted in the synthesis of partially substituted phases and strontium leaching at all-time points. The strontium silicate implanted in the animal model could not be retrieved in over half of the specimens showing the high rate of material digestion. Tissue histology showed that all materials caused inflammation after 30 days of implantation however this subsided and angiogenesis occurred after 180 days. Strontium was not detected in the local tissues or the peripheral organs while all calcium containing materials caused calcium deposition in the kidneys. The tricalcium silicate caused elemental migration of calcium and silicon in the local tissues shown by the elemental mapping but no deposition of calcium was identified in the peripheral organs verified by the assessment of the digested tissues. Strontium can substitute calcium in bioactive materials without adverse local or systemic effects.

Unravelling the effects of ibuprofen-acetaminophen infused copper-bioglass towards the creation of root canal sealant

Impact towards the tuneable characteristics of bioactive glasses (BAG) has been explored; as there is no root canal sealant till date with ideal characteristics competent enough to manoeuvre the perplexing root canal architecture. Combeite, calcite and traces of cuprorivaite crystalline phases were validated for material formation, in which Cu 2P [XPS] peak authenticating the presence of copper in bioglass network (Cu-BAG). Spherical and platelet-like morphologies were observed and the grain size of Cu-BAG (~100 nm) was lesser as compared to BAG (~ 1 µm). These particle distributions impacted the porosity, and dominant non-bridging oxygens in Cu-BAG influences ionic dissolution, which subsequently enhanced the mineralization. These bioactive materials were loaded with acetaminophen and ibuprofen, corresponding organic moieties was confirmed through FT-IR. These drugs loaded bioactive materials exhibited tremendous anti-inflammatory and anti-microbial behavior with better sealing ability. Drug loaded bioglass paste filled in biomechanically prepared root canal was estimated for sealing potential, mineralization, micro leakage, and fracture resistance properties. Hydroxyl apatite growth was noted on the sealants, flower like protuberance confirmed the sealing potential of the prepared material. Bioglass exhibited promising characteristics required in a root canal sealant. This investigation is a step further towards tailoring the properties of bioactive materials as promising candidates in root canal obturation and thereof.

Intrinsically radiopaque biomaterial assortments: a short review on the physical principles, X-ray imageability, and state-of-the-art developments

X-ray attenuation ability, otherwise known as radiopacity of a material, could be indisputably tagged as the central and decisive parameter that produces contrast in an X-ray image. Radiopaque biomaterials are vital in the healthcare sector that helps clinicians to track them unambiguously during pre and post interventional radiological procedures. Medical imaging is one of the most powerful resources in the diagnostic sector that aids improved treatment outcomes for patients. Intrinsically radiopaque biomaterials enable themselves for visual targeting/positioning as well as to monitor their fate and further provide the radiologists with critical insights about the surgical site. Moreover, the emergence of advanced real-time imaging modalities is a boon to the contemporary healthcare systems that allow to perform minimally invasive surgical procedures and thereby reduce the healthcare costs and minimize patient trauma. X-ray based imaging is one such technologically upgraded diagnostic tool with many variants like digital X-ray, computed tomography, digital subtraction angiography, and fluoroscopy. In light of these facts, this review is aimed to briefly consolidate the physical principles of X-ray attenuation by a radiopaque material, measurement of radiopacity, classification of radiopaque biomaterials, and their recent advanced applications.

Formulation and Characterization of a New Injectable Bone Substitute Composed PVA/Borax/CaCO3 and Demineralized Bone Matrix

The occurrence of bone-related disorders and diseases has dramatically increased in recent years around the world. Demineralized bone matrix (DBM) has been widely used as a bone implant due to its osteoinduction and bioactivity. However, the use of DBM is limited because it is a particulate material, which makes it difficult to manipulate and implant with precision. In addition, these particles are susceptible to migration to other sites. To address this situation, DBM is commonly incorporated into a variety of carriers. An injectable scaffold has advantages over bone grafts or preformed scaffolds, such as the ability to flow and fill a bone defect. The aim of this research was to develop a DBM carrier with such viscoelastic properties in order to obtain an injectable bone substitute (IBS). The developed DBM carrier consisted of a PVA/glycerol network cross-linked with borax and reinforced with CaCO3 as a pH neutralizer, porosity generator, and source of Ca. The physicochemical properties were determined by an injectability test, FTIR, SEM, and TGA. Porosity, degradation, bioactivity, possible cytotoxic effect, and proliferation in osteoblasts were also determined. The results showed that the developed material has great potential to be used in bone tissue regeneration.

Preparing polycaprolactone scaffolds using electrospinning technique for construction of artificial periodontal ligament tissue

Objectives

The strategies of tissue-engineering led to the development of living cell-based therapies to repair lost or damaged tissues, including periodontal ligament and to construct biohybrid implant. This work aimed to isolate human periodontal ligament stem cells (hPDLSCs) and implant them on fabricated polycaprolactone (PCL) for the regeneration of natural periodontal ligament (PDL) tissues.

Methods

hPDLSCs were harvested from extracted human premolars, cultured, and expanded to obtain PDL cells. A PDL-specific marker (periostin) was detected using an immunofluorescent assay. Electrospinning was applied to fabricate PCL at three concentrations (13%, 16%, and 20% weight/volume) in two forms, which were examined through field emission scanning electron microscopy (FESEM). The isolated hPDLSCs were implanted on the fabricated PCL. After 21 days, FESEM was conducted to evaluate the implanted scaffolds, and an MTT assay was performed to characterize the biological response of the PCL scaffold at different cell exposure durations (24, 48, and 72 h).

Results

Periostin was expressed in the expanded PDL cells, and this result revealed that 20% weight/volume PCL scaffold with a pore size of more than 10 μm was the best. The growth rates of PDLSCs were high. Cytotoxicity test of fabricated PCL scaffold demonstrated no significant change in the cell viability when compared with the negative control and no deteriorating or inhibitory effect on growth after different durations.

Conclusions

A cell sheet was successfully formed by using PCL as a scaffold to cover dental implants and promote PDL cell attachment, proliferation, and growth for biohybrid implant construction.

Cytotoxic Effect of Niobium Phosphate Glass-based Gutta-Percha Points on Periodontal Ligament Fibroblasts In Vitro

INTRODUCTION

The outcome of root canal obturation might be affected by the chemical components of the chosen filling materials. Niobium phosphate glass-based gutta-percha (GNB) was proposed as a biomaterial-based obturation point. This study aimed to investigate the cytotoxic and cell modulation effects of GNB points on human periodontal ligament fibroblasts (PDLFs) in vitro.

METHODS

Human PDLFs were cultured for the assays. Extracts of regular gutta-percha (GP) points and GNB were obtained, serially diluted (1:5, 1:10, and 1:25), and used to stimulate PDLFs. A cell viability assay was performed using alamarBlue reagent (Molecular Probes, Waltham, MA), and reverse transcription quantitative polymerase chain reaction was used to assess the gene expression for collagen type I and cementum protein 1. One-way analysis of variance followed by the Tukey post hoc test was performed (P < .05).

RESULTS

Regular GP reduced cell viability only in pure extracts, whereas GNB exhibited cytotoxicity to PDLFs in pure extracts as well as 1/5 and 1/10 dilutions. The gene expression of collagen type I was down-regulated only in the GNB group (P < .05). The expression of cementum protein 1 remained unaltered by both tested materials.

CONCLUSIONS

The addition of niobium phosphate glass to GP points increased cytotoxicity, affecting PDLF viability and partially disturbing physiological cell function.

Modulation of neuronal cell affinity of composite scaffolds based on polyhydroxyalkanoates and bioactive glasses

The biocompatibility and neuron regenerating properties of various bioactive glass (BG)/polyhydroxyalkanoate (PHA) blend composites were assessed in order to study their suitability for peripheral nerve tissue applications, specifically as lumen structures for nerve guidance conduits. BG/PHA blend composites were fabricated using Bioactive glass® 45 S5 (BG1) and BG 1393 (BG2) with the 25:75 poly(3-hydroxyoctanoate/poly3-hydroxybutyrate), 25:75 P(3HO)/P(3HB) blend (PHA blend). Various concentrations of each BG (0.5 wt%, 1.0 wt% and 2.5 wt%) were used to determine the effect of BG on neuronal growth and differentiation, in single culture using NG108-15 neuronal cells and in a co-culture along with RN22 Schwann cells. NG108-15 cells exhibited good growth and differentiation on all the PHA blend composites showing that both BGs have good biocompatibility at 0.5 wt%, 1.0 wt% and 2.5 wt% within the PHA blend. The Young's modulus values displayed by all the PHA blend/BG composites ranged from 385.6 MPa to 1792.6 MPa, which are able to provide the required support and protective effect for the regeneration of peripheral nerves. More specifically, the tensile strength obtained in the PHA blend/BG1 (1.0 wt%) (10.0 ± 0.6 MPa) was found to be similar to that of the rabbit peroneal nerve. This composite also exhibited the best biological performance in supporting growth and neuronal differentiation among all the substrates. The neurite extension on this composite was found to be remarkable with the neurites forming a complex connection network.

In-vitro bioactivity evaluation and physical properties of an epoxy-based dental sealer reinforced with synthesized fluorine-substituted hydroxyapatite, hydroxyapatite and bioactive glass nanofillers

The purpose of this study was to evaluate the physical properties and bioactivity potential of epoxy-based dental sealers modified with synthesized bioactive glass (BAG), hydroxyapatite (HA) and fluorine substituted hydroxyapatite (FHA) nanoparticles.

The synthesized powders were incorporated at 10% and 20% into the epoxy-based dental sealer. The setting time, flow and solubility and microhardness of the modified and unmodified samples were examined. The bioactivity was evaluated using FESEM-EDX and elemental mapping, ATR-FTIR and XRD.

The flow value of all of the experimental groups except the FHA modified samples, was greater than 20 mm. Concerning solubility, no specimens exhibited more than 1% weight loss. The solubility value of the FHA groups was statistically significant lower than other groups (p ≤ 0.001). The mean hardness values of all of the modified samples were significantly higher than the unmodified group (p ≤ 0.001).

Regarding bioactivity, in vitro study revealed that after 3 days immersion in SBF a compact and continuous calcium phosphate layer formed on the surface of epoxy sealers containing BAG and HA nanoparticles.

Based on these results, the addition of BAG and HA nanoparticles did not adversely alter the physical properties of epoxy sealers. Additionally, they improved the in vitro bioactivity of the epoxy sealer.

•

Since root canal sealers are in direct contact with the periapical tissue, ideally, they should be composed of a bioactive material.

•

It is important that the added bioactive fillers don't adversely affect the physical properties of the material.

Regenerating a monoblock to obturate root canalsvia a mineralising strategy

To develop a novel strategy for sealing and obturating dental root canals by tooth-like tissue regeneration, premolars with mature root apices were freshly collected, and root canals were prepared by following the clinical protocols in vitro. The teeth were immersed in supersaturated calcium and phosphate solution containing gallic acid and fluoride. At certain intervals, the dental roots were taken out, and their mineral precipitates were characterised by scanning electron microscopy, energy-dispersive spectroscopy mapping, X-ray diffraction and transmission electron microscopy. The cytocompatibility of the mineralizing products were evaluated with rabbit bone-marrow-derived mesenchymal stem cells in vitro. Results showed that the precipitates were mainly composed of fluoridated hydroxyapatite with ahexagonal prism morphology. Fluoridated hydroxyapatite initially nucleated and grew from the root canal dentine surface to the root canal centre. The fluoridated hydroxyapatite precipitate and root canal dentine intergraded together such that the interface became hardly distinguishable. The fluoridated hydroxyapatite precipitate grew into and obturated the dentinal tubules. In the root canal, the regenerated fluoridated hydroxyapatite densely packed and bundled together with a c-axis extension. After 7 days of mineralisation, the root canal was completely obturated, and the apical foramen was sealed. The mineralizing products had good biocompatibility with the cells, and the cells grew well on the mineralized surface. Biomimetic mineralisation strategy provides a novel means to regenerate tooth-like tissue to seal the root canal system permanently other than by passive synthetic material filling.