Antibacterial activity of particulate Bioglass® against supra- and subgingival bacteria

Assessment of antimicrobial effect of Biosilicate® against anaerobic, microaerophilic and facultative anaerobic microorganisms

This study assessed the antimicrobial activity of a new bioactive glass-ceramic (Biosilicate®) against anaerobic, microaerophilic, and facultative anaerobic microorganisms. Evaluation of the antimicrobial activity was carried out by three methods, namely agar diffusion, direct contact, and minimal inhibitory concentration (MIC). For the agar diffusion technique, bio glass-ceramic activity was observed against various microorganisms, with inhibition haloes ranging from 9.0 ± 1.0 to 22.3 ± 2.1 mm. For the direct contact technique, Biosilicate® displayed activity against all the microorganisms, except for S. aureus. In the first 10 min of contact between the microorganisms and Biosilicate®, there was a drastic reduction in the number of viable cells. Confirming the latter results, MIC showed that the Biosilicate® inhibited the growth of microorganisms, with variations between ≤ 2.5 and 20 mg/ml. The lowest MIC values (7.5 to ≤ 2.5 mg/ml) were obtained for oral microorganisms. In conclusion, Biosilicate® exhibits a wide spectrum of antimicrobial properties, including anaerobic bacteria.

A review of the biological response to ionic dissolution products from bioactive glasses and glass-ceramics

Several inorganic materials such as special compositions of silicate glasses, glass-ceramics and calcium phosphates have been shown to be bioactive and resorbable and to exhibit appropriate mechanical properties which make them suitable for bone tissue engineering applications. However, the exact mechanism of interaction between the ionic dissolution products of such inorganic materials and human cells are not fully understood, which has prompted considerable research work in the biomaterials community during the last decade. This review comprehensively covers literature reports which have investigated specifically the effect of dissolution products of silicate bioactive glasses and glass-ceramics in relation to osteogenesis and angiogenesis. Particularly, recent advances made in fabricating dense biomaterials and scaffolds doped with trace elements (e.g. Zn, Sr, Mg, and Cu) and investigations on the effect of these elements on the scaffold biological performance are summarized and discussed in detail. Clearly, the biological response to artificial materials depends on many parameters such as chemical composition, topography, porosity and grain size. This review, however, focuses only on the ion release kinetics of the materials and the specific effect of the released ionic dissolution products on human cell behaviour, providing also a scope for future investigations and identifying specific research needs to advance the field. The biological performance of pure and doped silicate glasses, phosphate based glasses with novel specific compositions as well as several other silicate based compounds are discussed in detail. Cells investigated in the reviewed articles include human osteoblastic and osteoclastic cells as well as endothelial cells and stem cells.

Antibacterial effects of sol-gel-derived bioactive glass nanoparticle on aerobic bacteria

The aim of this work was to evaluate the antibacterial effect of bioactive glass nanopowders. The 58S, 63S, and 72S compositions were prepared via the sol-gel technique. Characterization techniques such as X-ray diffraction, transmission electron microscopy (TEM), Zetasizer, and X-ray fluorescent were used. The antibacterial activity was studied using Escherichia coli, Pseudomonas aeruginosa, Salmonella typhi, and Staphylococcus aureus. Cytotoxicity of the samples was evaluated using mouse fibroblast L929 cell line. The chemical compositions of the prepared samples were as predicted, and the particle size of the samples with an amorphous structure mainly ranged over 20-90 nm. At broth concentrations below 50 mg/mL, they showed no antibacterial activity. The 58S showed the highest antibacterial activity with the minimum bactericidal concentrations of 50 and 100 mg/mL for E. coli plus S. aureus and for P. aeruginosa, respectively. The 63S exhibited bactericidal and bacteriostatic effects on E. coli and S. aureus at concentrations of 100 and 50 mg/mL, respectively, at an minimum bactericidal concentrations of 100 mg/mL. However, 72S bioactive glass nanopowder showed no antibacterial effect. They showed no cytotoxicity. It was concluded that bioactive glass nanopowders could be considered as good candidates for the treatment of oral bone defects and root canal disinfection. (c) 2010 Wiley Periodicals, Inc. J Biomed Mater Res, 2010.

Bioactive glass S53P4 as bone graft substitute in treatment of osteomyelitis

Bioactive glass (BAG)-S53P4 is an osteoconductive bone substitute with proven antibacterial and bone bonding properties. In a multicentre study 11 patients with verified chronic osteomyelitis in the lower extremity and the spine were treated with BAG-S53P4 as a bone substitute. The cavitary bone defect and the surrounding of a spinal implant were filled with BAG-S53P4. The most common pathogen causing the infection was Staphylococcus aureus. The mean follow-up was 24 months (range 10-38). BAG-S53P4 was well tolerated. Nine patients healed without complications. One patient who achieved good bone formation sustained a superficial wound infection due to vascular problems in the muscle flap, and one patient had an infection due to a deep haematoma. This study shows that BAG-S53P4 is a good and well-tolerated bone substitute, and can be used in treatment of osteomyelitis with good primary results.

Antibacterial effects and dissolution behavior of six bioactive glasses

Dissolution behavior of six bioactive glasses was correlated with the antibacterial effects of the same glasses against sixteen clinically important bacterial species. Powdered glasses (<45 microm) were immersed in simulated body fluid (SBF) for 48 h. The pH in the solution inside the glass powder was measured in situ with a microelectrode. After 2, 4, 27, and 48 h, the pH and concentration of ions after removing the particles and mixing the SBF were measured with a normal glass pH electrode and ICP-OES. The bacteria were cultured in broth with the glass powder for up to 4 days, after which the viability of the bacteria was determined. The antibacterial effect of the glasses increased with increasing pH and concentration of alkali ions and thus with increased dissolution tendency of the glasses, but it also depended on the bacterium type. The changes in the concentrations of Si, Ca, Mg, P, and B ions in SBF did not show statistically significant influence on the antibacterial property. Bioactive glasses showed strong antibacterial effects for a wide selection of aerobic bacteria at a high sample concentration (100 mg/mL). The antibacterial effects increased with glass concentration and a concentration of 50 mg/mL (SA/V 185 cm(-1)) was required to generate the bactericidal effects. Understanding the dissolution mechanisms of bioactive glasses is essential when assessing their antibacterial effects.

Surface modification of a Ti-7.5Mo alloy using NaOH treatment and Bioglass coating

The objective of this study was to propose a surface modification for a low-modulus Ti-7.5Mo alloy to initiate the formation of hydroxyapatite (HA) during in vitro bioactivity tests in simulated body fluid (SBF). Specimens of commercially pure titanium (c.p. Ti) and Ti-7.5Mo were initially immersed in a 15 M NaOH solution at 60 degrees C for 24 h, resulting in the formation of a porous network structure composed of sodium titanate (Na(2)Ti(5)O(11)). Afterwards, bioactive Bioglass particles were deposited on the surface of NaOH-treated c.p. Ti and Ti-7.5Mo. The specimens were then immersed in SBF at 37 degrees C for 1, 7 and 28 days, respectively. The apatite-forming ability of the NaOH-treated and Bioglass-coated Ti-7.5Mo was higher than that of the c.p. Ti under the same condition. The X-ray diffraction (XRD) and energy-dispersive X-ray spectroscopy (EDS) results indicated that the deposited amounts of calcium phosphate were much greater for the surface-treated Ti-7.5Mo than for the c.p. Ti, a finding attributable to or correlated with the higher pH value of the SBF containing surface-treated Ti-7.5Mo. Moreover, in the surface-treated Ti-7.5Mo, the pH value of the SBF approached a peak of 7.66 on the first day. A combination of NaOH treatment and subsequent Bioglass coating was successfully used to initiate in vitro HA formation in the surface of the Ti-7.5Mo alloy.

Spinal Fusion of an Unstable Atlantoaxial Fracture in a Completely Tetraplegic Patient Using Silicate-Substituted Calcium Phosphate

Bone graft harvesting from the iliac crest constitutes the gold standard in spinal surgery due to its osteogenic, osteoconductive and osteoinductive properties. Large amounts of autograft can provoke complications like donor site morbidity, pain and the need for a second operation. Therefore, research into bone graft substitutes is of great interest. Silicate-substituted calcium phosphate (Actifuse(TM) Synthetic Bone Graft, ApaTech Ltd, London) was used in combination with morselized corticocancellous graft in a transarticular stabilization (modified Magerl) of a completely tetraplegic patient with an unstable atlantoaxial fracture. Computed tomography showed bone bridging between the segment C1/C2, the surface of the implant and the remodeled bone at follow-up at 8 months. The use of silicate-substituted calcium phosphate as a bone graft extender in spinal surgery could be an alternative to autografting from the iliac crest. Vegetative symptoms are often underestimated but can be triggered by donor site morbidity or pain in patients after spinal cord injury.

In vitro colonization of an experimental silicone by Candida albicans

Denture soft-lining materials are exposed to the oral cavity for long periods and are in continuous contact with saliva, subject to inhibition of liquid molecules, and susceptible to colonization by microorganisms. The opportunist yeast Candida albicans is of particular concern in this context, being associated with denture plaque and denture-related stomatitis. In this study, penetration of C. albicans into an experimental silicone elastomer soft-lining material was investigated under batch and continuous culture conditions. A model "denture plaque" microcosm was also used. Increasing the filler concentration within the elastomer decreased penetration under both batch and continuous culture conditions. In continuous culture, C. albicans penetration was significantly greater in pure culture than in the presence of bacteria after 72-h incubation (p < 0.05).

Poly(3-hydroxybutyrate) multifunctional composite scaffolds for tissue engineering applications

Poly(3-hydroxybutyrate) (P(3HB)) foams exhibiting highly interconnected porosity (85% porosity) were prepared using a unique combination of solvent casting and particulate leaching techniques by employing commercially available sugar cubes as porogen. Bioactive glass (BG) particles of 45S5 Bioglass grade were introduced in the scaffold microstructure, both in micrometer ((m-BG), <5 microm) and nanometer ((n-BG), 30 nm) sizes. The in vitro bioactivity of the P(3HB)/BG foams was confirmed within 10 days of immersion in simulated body fluid and the foams showed high level of protein adsorption. The foams interconnected porous microstructure proved to be suitable for MG-63 osteoblast cell attachment and proliferation. The foams implanted in rats as subcutaneous implants resulted in a non-toxic and foreign body response after one week of implantation. In addition to showing bioactivity and biocompatibility, the P(3HB)/BG composite foams also exhibited bactericidal properties, which was tested on the growth of Staphylococcus aureus. An attempt was made at developing multifunctional scaffolds by incorporating, in addition to BG, selected concentrations of Vitamin E or/and carbon nanotubes. P(3HB) scaffolds with multifunctionalities (viz. bactericidal, bioactive, electrically conductive, antioxidative behaviour) were thus produced, which paves the way for next generation of advanced scaffolds for bone tissue engineering.

The effect of composition on ion release from Ca-Sr-Na-Zn-Si glass bone grafts

Controlled delivery of active ions from biomaterials has become critical in bone regeneration. Some silica-based materials, in particular bioactive glasses, have received much attention due to the ability of their dissolution products to promote cell proliferation, cell differentiation and activate gene expression. However, many of these materials offer little therapeutic potential for diseased tissue. Incorporating trace elements, such as zinc and strontium, known to have beneficial and therapeutic effects on bone may provide a more viable bone graft option for those suffering from metabolic bone diseases such as osteoporosis. Rational compositional design may also allow for controlled release of these active ions at desirable dose levels in order to enhance therapeutic efficacy. In this study, six differing compositions of calcium-strontium-sodium-zinc-silicate (Ca-Sr-Na-Zn-Si) glass bone grafts were immersed in pH 7.4 and pH 3 solutions to study the effect of glass composition on zinc and strontium release in a normal and extreme physiological environment. The zinc release levels over 30 days for all zinc-containing glasses in the pH 7.4 solution were 3.0-7.65 ppm. In the more acidic pH 3 environment, the zinc levels were higher (89-750 ppm) than those reported to be beneficial and may produce cytotoxic or negative effects on bone tissue. Strontium levels released from all examined glasses in both pH environments similarly fell within apparent beneficial ranges--7.5-3500 ppm. Glass compositions with identical SrO content but lower ZnO:Na(2)O ratios, showed higher levels of Sr(2+) release. Whereas, zinc release from zinc-containing glasses appeared related to ZnO compositional content. Sustainable strontium and zinc release was seen in the pH 7.4 environment up to day 7. These results indicate that the examined Ca-Sr-Na-Zn-Si glass compositions show good potential as therapeutic bone grafts, and that the graft composition can be tailored to allow therapeutic levels of ions to be released.

Fine-tuning of bioactive glass for root canal disinfection

An ideal preparation of 45S5 bioactive glass suspensions/slurries for root canal disinfection should combine high pH induction with capacity for continuing release of alkaline species. The hypothesis of this study was that more material per volume of bioactive glass slurry is obtained with a micrometric material (< 5 microm particle size) or a micrometric/ nanometric hybrid, rather than a solely nanometric counterpart. This should correlate with alkaline capacity and antimicrobial effectiveness. Slurries at the plastic limit were prepared with test and reference materials in physiological saline. Total mass and specific surface area of glass material per volume were determined. Continuous titration with hydrochloric acid was performed, and antimicrobial effectiveness was tested in extracted human premolars mono-infected with E. faecalis ATTC 29212 (N = 12 per material). While the nanometric slurry had a 12-fold higher specific surface area than the micrometric counterpart, the latter had a considerably higher alkaline capacity and disinfected significantly better (Fisher's exact test, P < 0.05). The hybrid slurry behaved similarly to the micrometric preparation.

Surface silver-doping of biocompatible glasses to induce antibacterial properties. Part II: Plasma sprayed glass-coatings

A 57% SiO(2), 3% Al(2)O(3), 34% CaO and 6% Na(2)O glass (SCNA) has been produced in form of powders and deposited by plasma spray on titanium alloy and stainless steel substrates. The obtained coatings have been subjected to a patented ion-exchange treatment to introduce silver ions in the surface inducing an antibacterial behavior. Silver surface-enriched samples have been characterized by means of X-ray diffraction, SEM observation, EDS analysis, in vitro bioactivity tests, leaching tests by GFAAS (graphite furnace atomic adsorption spectroscopy) analyses, cells adhesion and proliferation, and antibacterial tests using Staphylococcus Aureus strain. In vitro tests results showed that the modified samples acquired an antimicrobial action against tested bacteria maintaining unaffected the biocompatibility of the glass. Furthermore the ion-exchange treatment can be successfully applied to glass-coated samples without affecting the properties of the coatings; the simplicity and reproducibility of the method make it suitable for glass or glass-ceramic coatings of different composition in order to produce coated devices for bone healing and/or prostheses, able to reduce bacterial colonization and infections risks.

Endodontic surgery with and without inserts of bioactive glass PerioGlas--a clinical and radiographic follow-up

OBJECTIVE

This study evaluated the use of bioactive glass, PerioGlas, after retrograde filling with Super EBA cement in the treatment of periapical bone destruction.

STUDY DESIGN

Healing outcomes were followed up after endodontic surgery in 186 teeth. Outcomes were divided into two groups according to follow-up time: short- and long-term. The EBA group (n = 110) underwent endodontic surgery and retrograde filling with EBA cement. In the EBA + PerioGlas group (n = 76), PerioGlas was embedded in the bone cavity after retrograde filling.

RESULTS

The success rate in the EBA + PerioGlas group was 72% compared with 56% in the Super EBA group at the short-term follow-up and 74% and 84%, respectively, at the long-term follow-up. Healing of periapical bone destruction classified as uncertain at the short-term follow-up was considered successful in two out of three cases at the long-term follow-up.

CONCLUSION

This study found that PerioGlas as bone substitute did not significantly improve endodontic healing outcome.

Study on antibacterial effect of 45S5 Bioglass

Previous studies have shown that bioactive glasses possessed antibacterial effect on common bacteria due to the high aqueous pH value caused by the bioactive glass dissolution. In the present study, the efficiency of the antibacterial effect of 45S5 Bioglass (45S5 BAG) against S. aureus, S. epidermidis and E. coli and its mechanism were investigated. The results showed that 45S5 BAG exhibited a strong antibacterial effect against the bacteria, and the sensitivity of gram-negative and gram-positive bacteria to Bioglass was different. Furthermore, a dose-dependent bacterial adhesion on 45S5 BAG particles and the formation of needle-like Bioglass debris were observed, which resulted in the damage of cell walls and inactivation of bacteria. The results suggested that both the high pH and bioglass debris on the surface of bacteria may be the possible mechanisms of the antibacterial effect of 45S5 BAG particulates.

Consil bioactive glass particles enhance osteoblast proliferation and maintain extracellular matrix production in vitro

Bioactive glasses are used clinically as bone implant materials as they are able to bond directly with bone. Studies in dogs have demonstrated the utility of Consil Bioglass synthetic bone graft particulate, a commercially available bioactive glass formulation, as a bone substitute for repair of bony defects. We evaluated the effect of Consil particles (500 microg/mL) on osteoblast proliferation and extracellular matrix (ECM) production at the cellular level in vitro. An osteoblast surrogate MG-63 cell line was incubated with Consil particles or medium alone for different time periods to determine the effect of Consil particles on proliferation and expression of ECM components. Osteoblasts remained viable and proliferated upon exposure to the particles, as shown by increased total DNA content. Cells incubated with Consil particles maintained expression levels of phenotype markers (type I collagen, osteocalcin, proteoglycans, and alkaline phosphatase) similar to control cells. Levels of secreted type I collagen and osteocalcin were time-dependent and similar to controls. This study verified the ability of Consil particles to enhance proliferation of osteoblast-like cells. The particles also maintained ECM production up to 21 days in culture. Our study supports the reported clinical utility of Consil particles for the repair of bony defects.

Bioactive glass as a bone substitute for spinal fusion in adolescent idiopathic scoliosis: a comparative study with iliac crest autograft

BACKGROUND

Iliac crest autograft is currently the gold standard material for spinal fusion. However, its use is limited by additional operative time, increased blood loss, and morbidity. Recently, a synthetic osteoconductive bone graft material composed of bioactive glass has been described, with high effectiveness in animal models. Its ability to achieve spinal fusion in human has never been reported. The aim of this study was to compare bioactive glass and iliac crest autograft as bone substitutes in the treatment thoracic adolescent idiopathic scoliosis (AIS).

METHODS

Eighty-eight consecutive patients underwent posterior spinal fusion for progressive thoracic AIS. There were 2 study groups based on the type of bone graft used: iliac crest autograft (n = 40) or bioglass (n = 48). A minimum 2-year follow-up was required. Medical data and radiographs were retrospectively analyzed and compared using unpaired t test and Mann-Whitney U test.

RESULTS

Mean follow-up was 40 months in the autograft group and 38 months in the bioglass group. In the autograft group, there were 2 infections (5%) and 3 mechanical failures (7.5%). One infection (2%) and 1 early mechanical failure (2%) occurred in the bioglass group. Loss of correction of the main thoracic curve between immediate postoperative and latest follow-up averaged 15.5% for autograft group and 11% for the bioglass group (P = 0.025). The mean (+/-SD) gain of frontal balance between immediate postoperative latest follow-up was 0.8 (+/-9.3) mm in the autograft group and 8.1 (+/-12) mm for the bioglass group (P = 0.005).

CONCLUSIONS

Results of this retrospective study suggest that bioglass is as effective as iliac crest graft to achieve fusion and maintain correction in AIS. Less complications were seen in the bioactive glass group, but the difference did not reach statistical significance. Bioactive glass can be proposed in the treatment of AIS, avoiding the morbidity of iliac crest harvesting. However, clinical and radiological outcomes need to be confirmed at long-term follow-up.

LEVEL OF EVIDENCE

Level III.

Do bioactive glasses convey a disinfecting mechanism beyond a mere increase in pH?

AIM

To test whether bioactive glasses kill microbiota via mineralization or the release of ions other than sodium.

METHODOLOGY

Flame-spray synthesis was applied to produce nanometric glasses of different sodium content and constant Ca/P ratio: 28S5, 45S5 and 77S. Calcium hydroxide and nanometric tricalcium phosphate (TCP) were used as controls. Apatite induction was monitored by Raman spectroscopy. Bovine dentine disks with adherent Enterococcus faecalis cells were exposed to test and control suspensions or buffered solutions for 1 h, 1 day and 1 week. Colony-forming units were counted and disks were inspected using scanning electron microscopy. Suspension supernatants and solutions were analysed for their pH, osmolarity, calcium and silicon content.

RESULTS

Sodium containing glasses induced pH levels above 12, compared with less than pH 9 with sodium-free 77S. Calcium hydroxide, 45S5 and 28S5 killed all bacteria after 1 day and lysed them after 1 week. TCP caused the highest apatite induction and substantial calcification on bacteria adhering to dentine, but did not reduce viable counts. 77S achieved disinfection after 1 week without visible apatite formation, whilst the buffer solution at pH 9 caused only minimal reduction in counts.

CONCLUSION

Bioactive glasses have a directly and an indirectly pH-related antibacterial effect. The effect not directly linked to pH is because of ion release rather than mineralization.

Antibacterial nanomedicine

Recent advances in the field of nanotechnology led several groups to recognize the promise of recruiting nanomaterials to the ongoing battle against pathogenic bacteria. A large battery of newly discovered and developed nanomaterials has been accumulating during the last decade, therefore, it could be anticipated that it should only be a matter of time until such preliminary nanomedicine applications are presented. We review some of these pioneering studies in which nanomaterials have been evaluated as potential therapeutics, antiseptics or disinfectants. These studies can be divided roughly into two groups. The first are studies of antibacterial nanomedicines that are based solely on synthetic (artificial) materials. The second group comprises studies of antibacterial nanomaterials that are based on biological substances used in their natural or in a modified form. We will discuss the physicochemical and antibacterial highlights of each material and present the future perspectives of this emerging field.

Antibacterial effect of bioactive glasses on clinically important anaerobic bacteria in vitro

Bioactive glasses (BAGs) of different compositions have been studied for decades for clinical use and they have found many dental and orthopaedic applications. Particulate BAGs have also been shown to have antibacterial properties. This large-scale study shows that two bioactive glass powders (S53P4 and 13-93) and a sol-gel derived material (CaPSiO II) have an antibacterial effect on 17 clinically important anaerobic bacterial species. All the materials tested demonstrated growth inhibition, although the concentration and time needed for the effect varied depending on the BAG. Glass S53P4 had a strong growth-inhibitory effect on all pathogens tested. Glass 13-93 and sol-gel derived material CaPSiO II showed moderate antibacterial properties.

Bioactive glass hydroxyapatite in fronto-orbital defect reconstruction

BACKGROUND

Synthetic bioactive ceramics and glasses have osteoconductive properties. These materials are capable of chemically bonding to the bone tissue. In addition, special bioactive glasses do not favor microbial growth. In this study, the clinical outcome of bioactive glass and hydroxyapatite in head and neck surgery was evaluated.

METHODS

In a retrospective series of 150 patients, 62 patients underwent reconstruction with frontal sinus obliteration after chronic frontal sinusitis, 65 patients were operated on for fronto-orbital traumas, and 23 patients underwent reconstruction after fronto-orbital tumor resections. These patients were evaluated for surgical procedures, reconstruction materials, complications, and functional outcomes.

RESULTS

Three of the 62 frontal sinus occlusions underwent operation (4.8 percent) during the follow-up of 5 years. The reoperations were caused by a new mucocele. In fronto-orbital reconstructions, we have reoperated on the orbital floor in four cases (7 percent). All 12 benign tumor patients and six of 11 malignant tumor patients survived during a follow-up of 3 years. Two of the 23 (9 percent) complicated tumor and trauma patients underwent reoperation because of a local mucocele.

CONCLUSIONS

Treatment of severe head and neck defects with biomaterial is a suitable alternative to conventional methods. Bioactive materials seem to be stable and reliable at clinical follow-up. The reconstructions with bioactive glass and hydroxyapatite are associated with good functional and aesthetic results without donor-site morbidity. However, more long-term outcomes of studied biomaterials are needed to determine whether they are capable of competing with traditional tissue grafts.

Bactericidal effects of bioactive glasses on clinically important aerobic bacteria

Bioactive glasses (BAGs) have been studied for decades for clinical use, and they have found many dental and orthopedic applications. BAGs have also been shown to have an antibacterial effect e.g., on some oral microorganisms. In this extensive work we show that six powdered BAGs and two sol-gel derived materials have a clear antibacterial effect on 29 clinically important bacterial species. We also incorporated a rapid and accurate flow cytometric (FCM) method to calculate and standardize the numbers of viable bacteria inoculated in the suspensions used in the tests for antibacterial activity. In all materials tested growth inhibition could be demonstrated, although the concentration and time needed for the effect varied depending on the BAG. The most effective glass was S53P4, which had a clear growth-inhibitory effect on all pathogens tested. The sol-gel derived materials CaPSiO and CaPSiO II also showed a strong antibacterial effect. In summary, BAGs were found to clearly inhibit the growth of a wide selection of bacterial species causing e.g., infections on the surfaces of prostheses in the body after implantation.

Surface modification of titanium implants using bioactive glasses with air abrasion technologies

A growing number of surface treated titanium implants are routinely used in dental and orthopaedic surgery, with a view to enhancing integration capacity with osseous tissue. This study examines the use of bioactive glass 45S5 as an alternative abrasive and osteoproductive surface modification material. Abrasive blasting of commercially pure titanium with bioactive glass 45S5 produced an irregular finish with a surface roughness average (S(a)) of 1.1 microm as determined by white light interferometry, backscattered and secondary electron microscopy. The roughness attained compares favourably with currently used implant designs. Further, Energy Dispersive X-ray Analysis (EDXA) and backscattered electron microscopy demonstrated that bioactive glass was distributed across the titanium surface and retained within fissures and roughened surface features. Being an osteoproductive material, this is advantageous as it is expected that the modified metallic surfaces will acquire osteopromotive properties, and thus be of benefit to the process of implantation in osseous tissue.

Antimicrobial effect of nanometric bioactive glass 45S5

Most recent advances in nanomaterials fabrication have given access to complex materials such as SiO(2)-Na(2)O-CaO-P(2)O(5) bioactive glasses in the form of amorphous nanoparticles of 20- to 60-nm size. The clinically interesting antimicrobial properties of commercially available, micron-sized bioactive glass 45S5 have been attributed to the continuous liberation of alkaline species during application. Here, we tested the hypothesis that, based on its more than ten-fold higher specific surface area, nanometric bioactive glass releases more alkaline species, and consequently displays a stronger antimicrobial effect, than the currently applied micron-sized material. Ionic dissolution profiles were monitored in simulated body fluid. Antimicrobial efficacy was assessed against clinical isolates of enterococci from persisting root canal infections. The shift from micron- to nano-sized treatment materials afforded a ten-fold increase in silica release and solution pH elevation by more than three units. Furthermore, the killing efficacy was substantially higher with the new material against all tested strains.

Clinical evaluation of platelet-rich plasma and bioactive glass in the treatment of intra-bony defects

BACKGROUND

There are limited numbers of studies focused on the using of platelet-rich plasma (PRP) combined with different types of bone substitutes in intra-bony defects.

AIM

The purpose of this study was to evaluate the effect of bioactive glass graft material (BG) with and without PRP on the clinical healing of intra-bony defects.

MATERIALS AND METHODS

Twenty-nine intra-bony defects were randomly treated with either PRP/BG or BG alone. Clinical parameters were recorded at baseline and repeated 9 months after surgery and surgical reentries were also performed.

RESULTS

The results showed that both treatment modalities were effective. Pocket depth reduction of 3.60 +/- 0.51 mm, clinical attachment gain of 3.3 +/- 1.77 mm and defect fill of 3.47 +/- 0.53 mm were noted in the PRP/BG group, with 3.29 +/- 1.68, 2.86 +/- 1.56 and 3.36 +/- 0.55 mm improvements, respectively, noted for the BG group. None of the differences between the two treatment modalities were statistically significant.

CONCLUSIONS

It is suggested that both PRP/BG combination and BG alone are effective in the treatment of intra-bony defects. The results also showed that using PRP with BG has no additional benefit in the reduction of pocket depth, clinical attachment gain and defect fill.

Factors Controlling Antibacterial Properties of Bioactive Glasses

Factors controlling the antibacterial ability of three bioactive glasses were studied by comparing the changes in the SBF during immersion of the glasses with their response to four microorganisms. After immersion of 100 mg/ml fine powder (<45μm) of the glasses in the SBF for 1, 2, 4, 8, 16, 27 and 48 hours, the immersion solutions were filtered and the pH in the bulk solution was measured. Ionic concentrations of Na, K, Ca, Mg, P and Si ions in the immersion solutions were determined by ICP-OES. The antibacterial activity of the glasses showed good correlation with the changes of the pH values in the SBF solutions. No correlation was found between the ionic concentration and the antibacterial ability of the three glasses against the four tested microorganisms. The results suggest that, the antimicrobial effect of the glass powder against the microorganisms tested is mostly dependent on the increase of the pH in the solution to values detrimental for the bacteria growth.

A comparative study on the disinfection potentials of bioactive glass S53P4 and calcium hydroxide in contra-lateral human premolars ex vivo

AIM

To evaluate the effects of bioactive glass S53P4 versus calcium hydroxide when used as dressings in contra-lateral human premolars infected with Enterococcus faecalis ATCC 29212.

METHODOLOGY

Pairs of contra-lateral premolar teeth plus single control premolars were obtained from 23 individuals aged 10-26 years undergoing orthodontic treatment. Root canals of teeth with fully formed apices (nine contra-lateral pairs, seven controls) were instrumented using a size 60 FlexoFiles 2 mm short of canal length. Canals with open apices (six contra-lateral pairs, four controls) were circumferentially instrumented using a FlexoFile. Root canals were rinsed with 1% sodium hypochlorite and 10% citric acid. Teeth were then suspended in tryptic soy broth (TSB) and autoclaved. Positive controls and study teeth were infected with E. faecalis ATCC 29212 for 2 weeks in TSB, while negative controls were kept in sterile TSB. Subsequently, contra-lateral premolars were dressed with bioactive glass S53P4 (BAG) or calcium hydroxide suspensions for 10 days. Dentine samples were obtained from teeth with fully formed apices using ISO-size 70, 80 and 90 FlexoFiles to working length and cultured. Teeth with open apices were fixed, fractured and examined using scanning electron microscopy (SEM).

RESULTS

Calcium hydroxide had a strong antibacterial effect and was significantly more effective than BAG in preventing residual bacterial growth (P < 0.01). SEM analysis revealed apparent substance-specific modes of action.

CONCLUSIONS

Calcium hydroxide was an effective disinfectant in human teeth.

Anti-gingivitis effect of a dentifrice containing bioactive glass (NovaMin) particulate

BACKGROUND

The objective of this pilot clinical trial was to evaluate the anti-gingivitis and anti-plaque effects of a dentifrice containing bioactive glass (NovaMin) compared with a placebo control dentifrice in a 6 weeks clinical study.

METHODS

The study design was a randomized, double-blinded, controlled clinical trial. One hundred volunteers took part in the study and were matched for plaque index (PLI), gingival bleeding index (GBI), age and gender. The protocol was reviewed and approved by the Ethical Committee of the University. The subjects received a supragingival prophylaxis to remove all plaque, calculus and extrinsic stain. Following the baseline examination, subjects were instructed to brush with their assigned dentifrice and toothbrush. The PLI and GBI were determined for the baseline and 6 weeks. The data were analysed using a repeated-measures anova conducted on the two dependent measures to compare the effect between the test and control group.

RESULTS

Ninety-five subjects finished the study. The results showed that the PLI (baseline=1.54, 6 weeks=1.29) and GBI (baseline=1.14, 6 weeks=0.47) were significantly reduced, respectively, over the 6 weeks period in the test group (p<0.001 for each measure). There was a 58.8% reduction in gingival bleeding and a 16.4% reduction in plaque growth. There was no difference of the PLI (baseline=1.60, 6 weeks=1.57) and GBI (baseline=1.18, 6-week=1.02) over the 6 week period in the control group.

CONCLUSION

This study demonstrated that a dentifrice containing NovaMin significantly improves oral health as measured by a reduction in gingival bleeding and reduction in supragingival plaque compared with a negative dentifrice over the 6 weeks study period.

Effect of Ion Release on Antibacterial Activity of Melt-Derived and Sol-Gel-Derived Reactive Ceramics

Four different bioreactive ceramics were prepared using a sol-gel method and a standard melting process. The aim was to study antibacterial effect of these materials on the growth of Staphylococcus epidermidis. The dissolution (Si and Ca ions) of fine (≤ 45 !m) ceramic powders in a tryptone soya broth (TSB) was investigated. Also the pH changes in TSB solution were measured. In addition the adherence of Enterococcus faecalis (Ef) to materials was investigated. The bacterial adhesion was studied using scanning electron microscopy (SEM). In the bacterial and the adhesion test, CaPSiO2 and S53P4 had the strongest antimicrobial effect against studied bacteria. It was shown that bioreactive sol-gel derived ceramic with sufficient high Ca ion release (> 270 ppm) can reach strong antibacterial effect also at lower pH values (< 9.6).

Dentin enhances the effectiveness of bioactive glass S53P4 against a strain of Enterococcus faecalis

OBJECTIVE

The aim of the current study was to test the impact of dentin powder on the antimicrobial efficacy of bioactive glass S53P4 (BAG).

STUDY DESIGN

BAG was suspended (preincubated) in saline at 37 degrees C for different time periods with or without human dentin powder, hydroxylapatite, or decalcified dentin. Subsequently, Enterococcus faecalis ATCC 29212 cells were added to these suspensions and bacterial recovery measured with and without the use of gentle sonication. Furthermore, survival of bacteria in test and control suspensions was assessed over time. Supernatants of suspensions were analyzed for their element contents using atomic absorption spectrophotometry. The effects of pH, silica, and osmolarity on E faecalis viability were assessed using specifically prepared solutions.

RESULTS

BAG preincubated with dentin powder caused a significant (P < .05) decrease in viability compared to pure BAG suspensions. This was not based on adherence of bacteria to solid particles or agglutination of the cells, because sonication did not increase bacterial yields. Hydroxylapatite and decalcified dentin did not increase BAG killing efficacy. The additive effect of BAG + dentin powder was dose dependent, occurred only with solids in suspension, and increased with suspension time. An augmented dissolution of glass components, especially silicon, was measured in BAG + dentin powder compared to pure BAG suspensions or counterparts containing hydroxylapatite or decalcified dentin. High osmolarity per se did not affect E faecalis viability, whereas high pH and silica levels did.

CONCLUSION

The observed phenomenon was related to an increased BAG dissolution triggered by dentin powder, causing elevated local pH and silica levels.

Formation of a nanostructured layer on bioglass particles of different sizes immersed in tris-buffered solution. N2 adsorption and HR-TEM/EDS analysis

Morphological and structural variations of particles of Bioglass with two different grain sizes reacted in Tris-buffered solution were analyzed by means of N(2) adsorption/desorption at 77 K and HR-TEM/EDS. A remarkable increase in specific surface area (ssa) was observed after the first hour of dissolution. A plateau value corresponding to an increase of at least 2 orders of magnitude was reached after 2 days of dissolution. The ssa increase was faster for the smaller particle size sample, and the ratio between the ssa of the starting samples was not maintained during dissolution. Both micro- and mesopores were formed at different stages of the reaction for the two samples. Increasing ssa was also connected to the formation of a microcrystalline structure rich in Ca and P, as shown by TEM images. The segregation of both a SiO(2)-rich amorphous phase and a Ca/P-rich crystalline phase was observed after the first hour of dissolution. After 2 days of reaction, Ca/P-rich particles made of fine aciculate crystals were found either in close contact with SiO(2) particles or deposited on a small SiO(2)-rich core. A preliminary analysis of TEM data showed the formation, together with hydroxy carbonate apatite, of different types of calcium phosphates not detectable by powder X-ray diffraction.

Surface Modifications of Bioglass Immersed in TRIS-Buffered Solution. A Multitechnical Spectroscopic Study

Bioglass 45S5 is used in the medical field as a bone regenerative material. In fact, when immersed in body fluid, a layer of hydroxy carbonate apatite (HCA), an analogue to the mineral phase that bones are made of, is deposited on its surface. A mechanism that would explain this process has been hypothesized and includes cation leaching from the glass to the solution and formation of both a silica-rich layer and a Ca/P-rich surface layer, prior to the actual crystallization of HCA. The present paper analyzes the dissolution of 2-mum-size particles of Bioglass in TRIS-buffered solution, focusing on the modifications occurring at the surface of the particles. Results from Transmission FT-IR, Raman, and X-ray Photoelectron Spectroscopy were compared in order to obtain this information. In all cases, precise spectral band assignments were obtained by comparing Bioglass spectra, before and after reaction, with the spectra registered on some selected reference samples. The results confirm the hypothesized mechanism of Bioglass reactivity and yield new insights on the surface modifications of the samples. In particular, the following is shown: the strength of the surface H-bonding system and of water coordination decreases during the reaction; surface carbonates, initially mainly bound to Na, are substituted by an increasing amount of Ca-bound carbonates; and the final calcium phosphate layer obtained is very similar, but not identical, to carbonated hydroxyapatite.

The effect of the topical administration of bioactive glass on inflammatory markers of human experimental gingivitis

Recent studies demonstrated that bioactive glass attenuated inflammatory reactions and bacterial growth in vitro. The aim of the present clinical study was to evaluate the effects of local bioactive glass-administration in vivo in subjects with experimental gingivitis. In each individual, contralateral teeth served as test and control over a 21-day non-hygiene (preventive phase) and a 7-day therapeutic phase. A 45S5 bioactive glass (10% solution) was applied daily (2 x 1 h) on the test teeth during the preventive and therapeutic phase of the study. Inflammation assessment was based on the plaque index record (PI), on the bleeding frequency (BOP) and the gingival crevicular fluid volume (GCF). Interleukin-1beta levels (IL-1beta) in the GCF were measured by ELISA. Bacterial deposits on teeth increased during the 21-days non-brushing period, with no difference in plaque accumulation between test and control sides. BOP levels were significantly reduced during the therapeutic phase by the application of bioactive glass. GCF-values showed a significant reduction on the test compared to control side during the preventive and therapeutic phase. IL-1beta counts decreased during the last 7 days of the study on the test side, but no significance was given. The topical application of 45S5 bioactive glass in humans with experimental gingivitis attenuated the clinical signs of inflammation, although the bacterial accumulation was not inhibited in this clinical trial.

Effect of pH and ionic strength on the reactivity of Bioglass® 45S5

Bioglass 45S5 is a silica-based melt-derived glass, used in medical field as a bone regenerative material because of the deposition of a layer of hydroxy carbonate apatite (HCA) on the surface of the glass when immersed in body fluid. The present paper studies the early steps of reaction of 2-microm sized particles of Bioglass, in solutions buffered with TRIS at different pH, by means of ICP-ES and FTIR spectroscopy. Only at pH 8 could a total reconstruction of the glass be observed, with the formation of both a silica and a calcium phosphate rich layers. At higher pH, selective dissolution of the glass was hindered by the immediate precipitation of a layer of calcium phosphate, whereas at lower pH a total breakdown of the glass occurred and no calcium phosphate precipitation was noted. The use of the ATR-liquid cell allowed the observation of the reaction in real time, and this showed that the process of silica formation is not separable from cation leaching from the glass, as well as the formation of the calcium phosphate rich layer.

Preliminary Evaluation of Bioactive Glass S53P4 as an Endodontic Medication In Vitro

Calcium hydroxide is the "gold standard" endodontic medication, but it may fail to eliminate certain facultative bacteria and yeasts found in root canal systems. In this study, standardized bovine dentin blocks infected with Enterococcus faecalis were treated with an aqueous calcium hydroxide or bioactive glass S53P4 (BAG) powder suspension. While calcium hydroxide was ineffective, the BAG suspension eliminated the infection in the sampled dentin layers after 5 days. In a direct exposure test, preincubation with human dentin boosted the BAG-killing efficacy against E. faecalis ATCC29212, Candida albicans CCUG19915, Pseudomonas aeruginosa ATCC9027, Streptococcus sanguis ATCC10556, and S. mutans ATCC25175. BAG placed in the root canals of extracted teeth did not alter root-dentin pH. Consequently, the conditions under which the microbiota were killed were not pH-mediated. Further studies are ongoing to help clarify the antimicrobial BAG effect in the presence of dentin.

Bioactive glass as a drug delivery system of tetracycline and tetracycline associated with β-cyclodextrin

The aim of this study was to evaluate the physical-chemical properties, in vivo biocompatibility and antimicrobial activity of bioactive glasses (BG) used as a controlled release device for tetracycline hydrochloride and an inclusion complex formed by tetracycline and beta-cyclodextrin at 1:1 molar ratio. The BG as well as their compounds loaded with tetracycline (BT) and tetracycline:beta-cyclodextrin (BTC) were characterized by FTIR spectroscopy, X-ray powder diffraction, differential scanning calorimetry and by scanning electron microscopy and energy dispersive spectroscopy. The in vivo test was carried out with female mice split into three groups treated with bioactive glass either without drugs, or associated with tetracycline, or with tetracycline:beta-cyclodextrin by subcutaneous implantation. The histological examination of tissue at the site of implantation showed moderate inflammatory reactions in all groups after 72 h. The bacterial effect was tested on A. actinomycetemcomitans suspended in BHI broth, with or without bioactive particles. A considerable bacteriostatic activity was found with BT and BTC glasses, as compared to plain glass. The presence of cyclodextrin was important to slow down the release of tetracycline for a long period of time and it was verified that the presence of tetracycline or its inclusion complex, tetracycline:beta-cyclodextrin, did not affect the bioactivity of the glass.