Bioactive Glass-ceramics Research Articles

Synthesis, characterization, bioactivity and cytotoxicity assessment of nano ZrO2 reinforced bioactive glass ceramics

Bioactive glass and glass ceramics have travelled a long way as biomaterials. Several research works have been devoted to improving mechanical properties, especially using various additives. Out of these, ZrO2-containing glass and glass ceramics have shown promising outcomes. In this present work, a set of 3 Nano-ZrO2 containing novel bioactive glass and glass ceramics of composition 37.5 nano-SiO2–(17-X)Al2O3–26.5CaO–11.5CaF2–7.5P2O5–X nano-ZrO2 (where, X= 0.75, 1.7, 2.7, all in mol %) were synthesized by melt-quenching technique. Standard characterization procedures were performed to assess the physical and chemical properties, structure and surface morphologies. In vitro bioactivity and cytotoxicity assessments were also done. Fluorapatite (Ca5(PO4)3F) and Anorthite (Ca(Al2Si2O8)) along with tetragonal Zirconia (t-ZrO2) at higher nano-ZrO2 content of 2.7 mol% were discovered as the primary crystalline phases. Adding nano-zirconia enhanced the glasses' thermal stability and the glass ceramics' micro-hardness. The formation of nanometer-size hydroxyapatite (HAp) on the glass-ceramics samples confirmed the good bioactive nature. The non-toxic nature of the samples towards living cells was demonstrated by cytotoxicity assessment.

Evaluation of Bioactive Glass Treatment for Dentin Hypersensitivity: A Systematic Review.

The aim of this systematic review is to compare home and office desensitizers containing bioactive glass with control groups in randomized controlled trials (RCT) conducted between 2018 and 2022. According to PRISMA guidelines, three electronic databases (Scopus, PubMed, and Cochrane Library) were searched for published scientific articles in October 2022. RCT with adult participants with dentin hypersensitivity (DH) diagnosed by evaporative, mechanical, or thermal stimulation, with a follow-up period and quantified pain assessment were included in the study. Studies that reported DH due to tooth restoration, crown preparation, bleaching, or periodontal surgery or used bioactive glass-ceramics were excluded. The quality of the studies was assessed using version 2 of the Cochrane Risk-of-Bias Tool for randomized studies (RoB 2 tool). Articles that were duplicative or unrelated to this study were excluded. Nine articles were selected for full-text evaluation, whereas two articles were rejected. The remaining seven reports were included in this review. The calcium sodium phosphosilicate group (CSPS) was not significantly different from the positive control groups. Compared with the control groups, fluoro calcium phosphosilicate (FCPS) may be the most effective long-term treatment option. In terms of DH symptom reduction, the FCPS group performed better than the CSPS group. CSPS at a concentration of 5-15% and FCPS at a concentration of 5% are effective in treating DH in adult participants.

Influence of iron oxide substitution on the magnetic interactions in sol–gel‐derived 45S5 bioactive glass–ceramics

AbstractMagnetic interactions in sol–gel‐derived bioactive magnetic glass–ceramics (MGCs) with compositions of (45 − x)SiO2·24.5CaO·24.5Na2O·6P2O5 xFe2O3 (2 ≤ x ≥ 15 wt.%) have been investigated using electron paramagnetic resonance (EPR), and temperature‐dependent magnetic susceptibility and magnetization (M–T) techniques. EPR spectra of the MGC samples revealed strong composition dependence in the intensity and linewidth of resonance absorptions at g ≈ 2.0 and g ≈ 4.3. EPR linewidth analysis showed the dominance of dipole–dipole interaction in MGC samples with iron oxide content ≤4 wt.% and a crossover to super‐exchange type interaction in samples with higher iron oxide content. Composition‐dependent magnetic interaction in these MGC could be related to Fe2+ and Fe3+ ion concentrations using high‐temperature magnetic susceptibility studies. Zero‐field cooled and field cooled M–T curves indicate different magnetic behavior for MGC samples with x ≤ 6 and x ≥ 8 wt.% iron oxide. Although the former show weak magnetic behavior, the latter exhibit superparamagnetic behavior which could be correlated with the percentage of magnetic phases present in each sample. These studies reveal composition‐dependent variation in dipolar and super‐exchange type interaction in the samples which could help in assessing these MGC for biomedical applications.

Phase transformation and mechanical properties of new bioactive glass-ceramics derived from CaO–P2O5–Na2O–B2O3–SiO2 glass system

This work investigates the role of sintering temperature on bioactive glass-ceramics derived from the new composition CaO–P2O5–Na2O–B2O3–SiO2 glass system. The sintering behaviour of the samples’ physical, structural, and mechanical properties is highlighted in this study. The experimental results indicated that the sintering process improved the crystallization and hardness of the final product. Results from XRD and FTIR showed the existence of carbonate apatite, pseudo-wollastonite, and wollastonite phases. From the results, the bioglass-ceramics sintered at 700 °C obtained the highest densification and optimum mechanical results. It had the value of 5.34 ± 0.21 GPa regarding microhardness and 2.99 ± 0.24 MPa m1/2 concerning fracture toughness, which falls in the range of the human enamel. Also, the sintered samples maintained their bioactivity and biodegradability after being tested in the PBS medium. The bioactivity does not affect but slows down the apatite formation rate. Overall results promoted the novel bioglass-ceramics as a candidate material for dental application.

Long-term results comparison after anterior cervical discectomy with BGS-7 spacer (NOVOMAX®-C) and allograft spacer: A prospective observational study.

Introduction: In an anterior cervical discectomy and fusion (ACDF), various types of graft materials including autograft, allograft, and synthetic graft have been used to achieve adequate spinal fusion. Allograft spacer is mainly used in cervical fusion, especially in the anterior approach. The synthetic bone graft material BGS-7(CaO-SiO2-P2O5-B2O3, bioactive Glass-Ceramics) can bind with surrounding bone tissue by forming a hydroxyapatite layer bone bridge, leading to faster graft osseointegration. This study was conducted to compare long-term clinical outcome of BGS-7 spacer and allograft spacer for anterior cervical discectomy and fusion surgery. Materials and Methods: From September 2014 to December 2016, Consecutive anterior cervical discectomy and fusion surgeries using a BGS-7 spacer (N = 18) and Allograft spacer (N = 26) were compared for postoperative clinical outcomes. Radiologic assessments were performed, and Instrumental failure, including breakage, cage migration, subsidence were observed and Fusion status were analyzed. Finite element analysis was performed for simulating mechanical stress between the vertebral body and implant. Clinical outcomes were evaluated using neck VAS, NDI, and JOA on the patient's final follow-up visits. Results: Among the 44 patients who underwent an anterior cervical discectomy and fusion surgery using the BGS-7 spacer and Allograft spacer, there were 30 men and 14 women. The average age at the operation was 47.69 ± 10.49 in allograft spacer and 51.67 ± 11.03 in BGS-7 spacer. The mean follow-up period was 89.18 ± 5.44months. Twenty three (88.46%) patients in allograft spacer and 20(100%) patients in BGS-7 spacer were demonstrated radiologic evidence of interbody fusion in last OPD, which accounts for fusion grade 4 or 5. Peak stresses were 343.85MPa in allograft spacer, and 132.55MPa in BGS-7 spacer. Long-term clinical outcomes including neck VAS, NDI, and JOA didn't show statistical differences between the two groups. There were no adverse events related to the BGS-7 spacer.10.3389/fbioe.2023.110046. Conclusion: The BGS-7 spacer demonstrated reliability as a spacer in anterior cervical discectomy and fusionF surgery without instrumental failure. Early stabilization with a bony bridge formation was observed at the intermediate follow-up period, and the long-term clinical outcome was favorable at more than 60months after surgery without any adverse events. Thus, the BGS-7 spacer is a safe and effective alternative to the allograft spacer in anterior cervical discectomy and fusion surgery.

Photosynthetic microporous bioactive glass ceramic beads for treating avascular osteonecrosis

Bioactive glass (BG) ceramics have attracted considerable attention as ideal bone grafts for treating avascular osteonecrosis owing to similarities in biological function with that of native bone. Metal ion-doped BGs exhibit outstanding biocompatibility, controllable biodegradability, excellent osteoinductivity, and angiogenic ability. Moreover, effective oxygen generation can support the healing of osteonecrotic defects. In this study, we developed simple sol–gel, gel-casting, and surface modification methods to fabricate photosynthetic microporous BG ceramic beads with improved therapeutic efficacy for avascular osteonecrosis by combining the oxygen generation ability, osteoconductivity, osteoinductivity, and angiogenic ability. The BG ceramic beads exhibited interconnected microporous structures with uniform micropores and unequiaxed grains, and this microstructure was not affected by Sr- and Cu-co-doping. Conversely, Sr- and Cu-co-doping, epigallocatechin gallate immobilization, and thylakoid coating affected the in vitro biological activity of the BG ceramic beads. Biological activity assays revealed that the thylakoid-coated photosynthetic microporous BG (BG12ET) ceramic beads promoted osteoblastic cell proliferation and endothelial cell tube formation more effectively than other ceramic beads. Therefore, BG12ET ceramic beads incorporated with osteoinductive and angiogenic factors can potentially provide a new generation of bone grafts for synergistic osteonecrosis therapy.

The effect of Phytosphingosine and bioactive glass-ceramics in preventing dental enamel erosion.

This study evaluated the effect of phytosphingosine (PHS) and bioactive glass-ceramic (Biosilicate) on dental enamel in terms of color alteration (ΔE), microhardness, and surface roughness when submitted to erosive challenge (EC). Sixty specimens of bovine teeth (6×6×2mm) were obtained. Initial color (Easyshade, VITA), KHN (HMV-2, Shimadzu), and Ra (SJ-201P, Mitutoyo) measurements were performed. Specimens were separated into groups according to treatments: PHS, 10% Biosilicate, PHS+10% Biosilicate, and artificial saliva (control) and submitted to EC with Coca-Cola for 2 min. This cycle was repeated 4 times daily/15 days. Between cycles, specimens remained in artificial saliva (2 h/37°C). After daily cycles, they were also stored in artificial saliva at 37ºC. Final color, microhardness, and surface roughness measurements were done. Color and KHN data were analyzed by one-way ANOVA, Tukey's test; and Ra, by 2-way ANOVA, repeated measures, and Tukey's test (p<.05). The highest ΔE occurred in Saliva+EC (p<.05). Groups treated with PHS presented lower color change than Saliva+EC (p<.05). All the groups presented mean values above the 50:50% perceptibility (50:50%PT) and acceptability (50:50%AT) thresholds, except for control that showed mean value above 50:50%PT but below 50:50%AT. Biosilicate+EC showed higher relative microhardness than Saliva+EC (p<.05), but was similar to PHS+EC and PHS+Biosilicate+EC. Final enamel surface roughness increased for all the groups (p<.05), except for the control. The Biosilicate may prevent enamel mineral loss induced by erosion better than saliva. The PHS associated or not to Biosilicate demonstrated better color stability than saliva.

Non-destructive processing of silver containing glass ceramic antibacterial coating on polymeric surgical mesh surfaces.

Surgical meshes composed of bioinert polymers such as polypropylene are widely used in millions of hernia repair procedures to prevent the recurrence of organ protrusion from the damaged abdominal wall. However, post-operative mesh infection remains a significant complication, elevating hernia recurrence risks from 3.6% to 10%, depending on the procedure type. While attempts have been made to mitigate these infection-related complications by using antibiotic coatings, the rise in antibiotic-resistant bacterial strains threatens their effectiveness. Bioactive glass-ceramics featuring noble metals, notably silver nanoparticles (AgNPs), have recently gained traction for their wide antibacterial properties and biocompatibility. Yet, conventional methods of synthesizing and coating of such materials often require high temperatures, thus making them impractical to be implemented on temperature-sensitive polymeric substrates. To circumvent this challenge, a unique approach has been explored to deposit these functional compounds onto temperature-sensitive polypropylene mesh (PP-M) surfaces. This approach is based on the recent advancements in cold atmospheric plasma (CAP) assisted deposition of SiO2 thin films and laser surface treatment (LST), enabling the selective heating and formation of functional glass-ceramic compounds under atmospheric conditions. A systematic study was conducted to identify optimal LST conditions that resulted in the effective formation of a bioactive glass-ceramic structure without significantly altering the chemical and mechanical properties of the underlying PP-M (less than 1% change compared to the original properties). The developed coating with optimized processing conditions demonstrated high biocompatibility and persistent antibacterial properties (>7 days) against both Gram-positive and Gram-negative bacteria. The developed process is expected to provide a new stepping stone towards depositing a wide range of functional bioceramic coatings onto different implant surfaces, thereby decreasing their risk of infection and associated complications.

Estimation of elastic modulus, fracture toughness and strength of 47.5B-derived bioactive glass-ceramics for bone scaffold applications: a nanoindentation study

The knowledge of the mechanical properties of glass–ceramic materials used in bone scaffolds is the key to the optimal design of tissue engineering devices. In this paper, the elastic properties and fracture toughness of silicate bioactive glass-ceramics based on the 47.5B parent composition were quantified for the first time through nanoindentation. Specifically, the effect of sintering temperature was investigated by testing samples sintered at six different temperatures. The samples sintered at higher temperatures exhibited elastic modulus and fracture toughness higher than those of the lower temperature samples. Both properties are comparable with those shown by similar bioactive glasses available in literature, supporting the mechanical suitability of the materials for bone applications. An estimation of tensile strength as a function of flaw size is also provided by means of fracture mechanics approaches.

Mn-Doped Glass–Ceramic Bioactive (Mn-BG) Thin Film to Selectively Enhance the Bioactivity of Electrospun Fibrous Polymeric Scaffolds

In recent years, significant progress has been made in the development of new technologies to meet the demand for engineered interfaces with appropriate properties for osteochondral unit repair and regeneration. In this context, we combined two methodologies that have emerged as powerful approaches for tissue engineering application: electrospinning to fabricate a nanofibrous polymeric scaffold and pulsed laser deposition to tune and control the composition and morphology of the scaffold surface. A multi-component scaffold composed of synthetic and natural polymers was proposed to combine the biocompatibility and suitable mechanical properties of poly(D,L-lactic acid) with the hydrophilicity and cellular affinity of gelatin. As part of a biomimetic strategy for the generation of bi-functional scaffolds, we coated the electrospun fibers with a thin film of a bioactive glass–ceramic material supplemented with manganese ions. The physico-chemical properties and composition of the bi-layered scaffold were investigated, and its bioactivity, in terms of induced mineralization, was tested by incubation in a simulated body fluid buffer. The processes of the inorganic film dissolution and the calcium phosphate phases growth were followed by microscopic and spectroscopic techniques, confirming that a combination of bioactive glass–ceramics and nanofibrous scaffolds has promising potential in the regeneration of osteochondral tissue due to its ability to induce mineralization in connective tissues.

Bioactive antibacterial borate glass and glass-ceramics

This work aimed to study bioactive glass-ceramics obtained by controlled crystallization, as a function of the heat treatment time, in system 59.5B2O3-2P2O5-9.5CaO-19.5Na2O-9CaF2-0.5Ag2O (mol %). The samples were prepared by the melt-quench method, and thermally treated at 530 °C, with different times: 0, 4, 8, 12, 24 and 36 h. Results of DTA, XRD, FTIR, density and molar volume are shown. The results of XRD revealed the development of crystalline phases during the heat treatment (CaNaB5O9, Ca3(PO4)2, Na2B6O10 and Ag°). The percentage of crystallization and in the size of the crystallite show increases with the time of the heat treatment, as expected. In vitro bioactivity of the samples was analyzed by immersion in SBF for 7, 14, 21 and 28 days. XRD patterns and FTIR spectra after immersion proved HA precipitation. The pH results reveal a higher ion exchange rate for the crystallized samples. This can be associated with the microstructure changes that occur on the surface of the samples during the heat treatment and the solubility of the crystalline phases. In addition, glass and crystallized samples showed antibacterial action against E. coli, independently of the crystallization time. It is possible to conclude that glass-ceramics can potentially be used as biomaterials in the treatment of bone fractures.

The effect of borate bioactive glass ceramics containing silver nanoparticles on removal physiognomies of methylene blue

Several studies have been carried out with several materials on the removal of methylene blue from water. Well-known bioactive glass 46S5.2 was prepared by complete replacement of the silicate partner with boron oxide via a two-step crystallization process, in particular its glass-ceramic derivative. The characterization techniques for ceramic sample were performed such as Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), scanning electron microscope (SEM) and energy dispersive X-ray (EDX). Transmission electron microscope (TEM) was employed to ensure that silver addition reaches to the nanoscale. UV/Vis. optical absorption spectroscopy was utilized in the retracing process of methylene blue adsorption from its contaminated water. The antimicrobial activity of the prepared sample was also studied extensively. Also for the prepared glass-ceramic samples, the reusability test was carried out to ensure that they could be used more than once in water treatment applications.

Superparamagnetic and highly bioactive SPIONS/bioactive glass nanocomposite and its potential application in magnetic hyperthermia

Magnetic bioactive glass-ceramics are biomaterials applied for magnetic hyperthermia in bone cancer treatment, thereby treating the bone tumor besides regenerating the damaged bone. However, combining high bioactivity and high saturation magnetization remains a challenge since the thermal treatment step employed to grow magnetic phases is also related to loss of bioactivity. Here, we propose a new nanocomposite made of superparamagnetic iron oxide nanoparticles (SPIONs) dispersed in a sol-gel-derived bioactive glass matrix, which does not need any thermal treatment for crystallization of magnetic phases. The scanning and transmission electron microscopies, X-ray diffraction, and dynamic light scattering results confirm that the SPIONs are actually embedded in a nanosized glass matrix, thus forming a nanocomposite. Magnetic and calorimetric characterizations evidence their proper behavior for hyperthermia applications, besides evidencing inter-magnetic nanoparticle interactions within the nanocomposite. Bioactivity and in vitro characterizations show that such nanocomposites exhibit apatite-forming properties similar to the highly bioactive parent glass, besides being osteoinductive. This methodology is a new alternative to produce magnetic bioactive materials to which the magnetic properties only rely on the quality of the SPIONs used in the synthesis. Thereby, these nanocomposites can be recognized as a new class of bioactive materials for applications in bone cancer treatment by hyperthermia.

LZS bioactive glass-ceramic scaffolds: Colloidal processing, foam replication technique and mechanical properties to bone tissue engineering

Scaffolds are used in bone replacement because present biocompatibility, three-dimensional structure, and high porosity. However, despite the efforts, there are still significant barriers to the development of reliable, synthetic scaffolds to repair large defects is one of the challenges of regenerative medicine. Therefore, innovative solutions are needed better to meet the requirements of a minimally invasive approach while providing adequate vascularity and strength and mechanical reliability. In this sense, the obtainment of a material that satisfies all these requirements is very important. This work aims to evaluate the mechanical properties of glass-ceramic scaffolds of the LZS (Li2O–ZrO2–SiO2) system produced by the replica method. For this, detailed colloidal processing was carried out to identify the solids content, amount of dispersant, and the binder most suitable to produce scaffolds. Finally, the mechanical reliability of the most suitable composition was evaluated by Weibull statistics. Suspensions containing 47 vol% of LZS relative to glass and 0.2 wt % of dispersant were used. In addition, dispersion times and the amount of binder were adjusted. Scaffolds of bioactive glass-ceramics were obtained at 900 °C, replicating polyurethane foams. Then they were morphologically, structurally, and mechanically characterized. The obtained bioactive glass-ceramic scaffolds presented porosity up to 83%, compressive strengths comparable to those of trabecular bone, up to 1.3 MPa, in addition to pore size >300 μm, desirable to favor biological interests destined to the regeneration and formation of bone tissue, demonstrating the possibility of its use as a material for bone replacement or filling. The Weibull modulus found for the glass-ceramic scaffolds produced is 4.18: within the expected range of mechanical reliability for application in bone regeneration.

A study of bioactive glass-ceramic's mechanical properties, apatite formation, and medical applications.

Apparently, bioactive glass–ceramics are made by doing a number of steps, such as creating a microstructure from dispersed crystals within the residual glass, which provides high bending strength, and apatite crystallizes on surfaces of glass–ceramics when calcium ions are present in the blood. Apatite crystals grow on the glass and ceramic surfaces due to the hydrated silica. These materials are biocompatible with living bone in a matter of weeks, don't weaken mechanically or histologically, and exhibit good osteointegration as well as mechanical properties that are therapeutically relevant, such as fracture toughness and flexural strength. As part of this study, we examined mechanical properties, process mechanisms involved in apatite formation, and potential applications for bioactive glass–ceramic in orthopedic surgery, including load-bearing devices.

Bioactive glass-ceramic for bone tissue engineering: an in vitro and in vivo study focusing on osteoclasts.

Despite the crucial role of osteoclasts in the physiological process of bone repair, most bone tissue engineering strategies have focused on osteoblast-biomaterial interactions. Although Biosilicate® with two crystalline phases (BioS-2P) exhibits osteogenic properties and significant bone formation, its effects on osteoclasts are unknown. This study aimed to investigate the in vitro and in vivo effects of BioS-2P on osteoclast differentiation and activity. RAW 264.7 cells were cultured in osteoclastogenic medium (OCM) or OCM conditioned with BioS-2P (OCM-BioS-2P), and the cell morphology, viability, and osteoclast differentiation were evaluated. BioS-2P scaffolds were implanted into rat calvarial defects, and the bone tissue was evaluated using tartrate-resistant acid phosphatase (TRAP) staining and RT-polymerase chain reaction (PCR) after 2 and 4 weeks to determine the gene expressions of osteoclast markers and compare them with those of the bone grown in empty defects (Control). OCM-BioS-2P favored osteoclast viability and activity, as evidenced by an increase in the TRAP-positive cells and matrix resorption. The bone tissue grown on BioS-2P scaffolds exhibited higher expression of the osteoclast marker genes (Ctsk, Mmp 9, Rank) after 2 and 4 weeks and the RankL/Opg ratio after 2 weeks. Trap gene expression was lower at 2 weeks, and a higher number of TRAP-stained areas were observed in the newly formed bone on BioS-2P scaffolds at both 2 and 4 weeks compared to the Controls. These results enhanced our understanding of the role of bioactive glass-ceramics in bone repair, and highlighted their role in the modulation of osteoclastic activities and promotion of interactions between bone tissues and biomaterials.

The effect of vanadium ferrite doping on the bioactivity of mesoporous bioactive glass-ceramics.

Bioactive glasses are highly reactive surface materials synthesized by melting or sol–gel techniques. In this study, mesoporous bioactive glass-ceramics doped with different amounts of vanadium and iron ((60−(x + y)) SiO2–36CaO–4P2O5–xV2O5–yFe2O3, x and y between 0, 5 and, 10 mole%) were synthesized using a sol–gel method. Then, their effects on particle morphology and the biomineralization process were examined in simulated body fluid (SBF). N2 adsorption isotherm analysis proved that the samples have a mesoporous structure. In addition, the Fourier-transform infrared spectroscopy (FTIR) spectra of the samples after soaking in SBF for various periods (7, 14, and 21 days) confirmed the presence of new chemical bonds related to the apatite phase, which is in accordance with scanning electron microscopy (SEM) observations. X-ray diffraction (XRD) patterns of the samples after SBF soaking showed that lower amounts of vanadium and iron were associated with the formation of a stable and more crystalline phase of hydroxyapatite. The MTT results showed that the cell viability of mesoporous bioactive glass containing 5% V2O5 remains more than 90% over 7 days, which indicates the biocompatibility of the samples. To conclude, further studies on these formulations are going to be carried out in future investigations for chemohyperthermia application.

Immobilization of bioactive glass ceramics @ 2D and 3D polyamide polymer substrates for bone tissue regeneration

The osteoinductivity of bioactive glass ceramics (BGCs) is dependent on their ability to effectively interact with the surrounding physiological environment and influence the fate of target cells; however, masking and poor dispersion can negatively influence bioactivity. Here, we address this problem via a simple fabrication method of assembling highly ordered and aligned arrays of BGC nanoneedle-like structures (@) on the outer surface of various polyamide 6 (PA6) substrates (casted film, 3D printing filaments, electrospun fibre mats) by ion dissociation. The staggered-like nanoneedles of BGC@PA6 substrates with excellent uniform dispersion showed favourable cell viability, proliferation, and spreading of MC3T3 osteoblast-like cells. Moreover, the immobilized BGC nanoneedles induced osteogenic differentiation and accelerated the expression of late osteoblast marker genes, compared to the control group. Furthermore, the BGC@PA6 composite showed high affinity for bone-like apatite formation when incubated in physiological body fluids. These findings suggest that the unique dispersion of BGCs@PA6 substrates with nanostructure features make them attractive candidates for bone tissue regeneration and open avenues for future investigation into exploiting these properties for bone tissue engineering. Importantly, this work provides a novel concept for in-situ immobilization of BGC with distinctive topographical features onto polymer substrates simulating natural bone structure.

Effect of Additional Zirconia on Fracture Mechanics of Bioactive Glass-ceramics Using Digital Image Correlation

Bioactive glass-ceramic is used as a replacement material for bone tissue due to its compatibility, bioactivity, and the ability to form a crystallized hydroxyapatite layer, which is similar in composition and structure to the inorganic component of the bone mineral phase. In this paper, bioglass-ceramic was toughened using zirconia to improve its mechanical behaviour (i.e. crack opening dsplacement and fracture toughness). The fracture toughness of the bioactive glass cerami/zirconia composite was measured using three-point bending technique. Digital Image Correlation (DIC) technique was utilized for visualized the crack initiation and calculation the crack opening displacement (COD) at the tip and mouth of the crack and measuring of the crack propagation of the bioactive glass cerami/zirconia composite. The results indicated that the incorporation of the zirconia particles improved the measured fracture toughness of the BGC/ZrO2 composite. The toughness of composite bioceramics is enhanced due to crack branching and crack deflection due to the presence of zirconia particles.

Optimizing the microstructure of a new machinable bioactive glass-ceramic

ObjectivesThis study aimed to optimize the crystallization process and the microstructure of a new bioactive glass-ceramic (GC) previously developed by our research group to obtain machinable glass-ceramics. MethodsDifferential scanning calorimetry (DSC) analyses were conducted to explore the characteristic temperatures and construct a semi-quantitative nucleation curve. The GC specimens were characterized by X-ray diffraction (XRD) and Rietveld refinement. Their brittleness index (B) and machinability were characterized and compared with IPS e.max-CAD®. Their Young's modulus, fracture toughness, and hardness were assessed. ResultsWe found that the maximum crystal nucleation rate temperature of this GC is ~470 °C. Treatments were designed based on the 1st DSC peak onset (570 °C), 1st peak offset (650 °C), and 2nd peak offset (705 °C) crystallization temperatures of lithium metasilicate (LS, LiSi2O3) and lithium disilicate (LS2, Li2Si2O5). Rietveld refinement indicated an increase in LS2 and a reduction in LS and amorphous phase for increased temperatures and longer treatment times. Their B values indicate good machinability compared with that of the control group based on statistical analyses. As expected, lower levels of LS2 increase the machinability regardless of the rotation speed adopted, leading to a greater depth of cut and reduced Edge Chipping Damage Depth (ECDD). ConclusionThis bioactive GC with optimized microstructure presents high machinability. For treatment temperatures above 570 °C, the number of elongated LS2 crystals increases and decreases the amorphous phase content, which reduce the machinability of the GC, and should therefore be avoided. The best results were obtained using heat treatment at 570 °C, which produces LS crystals embedded in a glassy matrix (67%) with small contents of secondary phases.