Bioactive Glass as a Bone Graft Substitute

 

Bioactive Glass as a Bone Graft Substitute

Posted Krista Grayson on May 16, 2018

Between 1992 and 2007, bone grafting was used in the treatment of almost two million patients in the United States.1 Bone grafts are used to facilitate the healing of complex bone trauma. This may be a multiple fracture or non-union of a long bone fracture, loss of bone due to disease, or surgical implantation of devices, like joint replacements, plates, or screws.

Bone grafting typically uses bone from another part of the patient’s body, such as ribs, hips, or pelvis, (an autograft) or bone harvested from a deceased donor or a cadaver that has been cleaned and stored in a tissue bank (an allograft). 

Despite grafting markedly improving bone regeneration and clinical outcomes after severe bone injury or loss, there is still room for improvement. Researchers continue to investigate ways to enhance bone grafting techniques and provide faster and denser bone regeneration with lower morbidity.

One such development has been the use of bone graft substitutes, such as demineralized bone matrix, calcium phosphates, collagen- /hydroxyapatite-based substitutes, and bone morphogenetic proteins. Although autologous bone grafting was considered to be the preferred bone grafting modality,2 there is a trend towards favoring artificial bone grafts over autografts since they are readily available and obviate the need for additional surgery. However, bone graft substitutes can have limitations regarding strength under torsion.

Bioactive glass, by virtue of its biocompatibility, strength and range of achievable properties, has been widely used to facilitate bone repair and provide support in tissue engineering.3

The Different Types of Bone Grafting

Bone grafting is a surgical procedure that is beneficial for repairing bones that have been severely damaged by trauma and for replacing bone that is missing as a result of either trauma or disease. It can also be used to strengthen bone at the site of an implant, be that a joint replacement, screw or dental implant. The bone graft provides a framework to support and encourage the growth of new, living bone.

Autografts have long been considered the preferred means of bone grafting since they do not carry the risk of rejection. However, these necessitate additional surgery, which increases patient morbidity and the risk of infection. Furthermore, there may be issues with availability finding a suitable site to harvest bone of the needed shape and size.

Allografts obviate the need for additional incisions but carry the risk of immune response preventing the graft from being accepted. There is also still the potential for availability issues since the donated bone needs to be tissue matched with the patient. 

A third option is not to rely on bone at all for the graft, but instead to use a man-made substitute. A range of different materials, including calcium phosphates, collagen, hydroxyapatite, have been investigated for use in bone grafting and are readily available. When using bone substitutes the nature of the materials must be carefully considered in terms of biocompatibility, resorption rate and strength.

Bone Graft Substitutes

The formation of new bone requires three key processes: osteogenesis (synthesis of new bone), osteoinduction (recruitment of stem cells and their differentiation into bone cells), and osteoconduction (the development of adequate blood supply to the new bone and correct structuring of the new bone cells). Bone graft substitutes are designed to facilitate and enhance these processes to promote rapid development of strong new bone.

Bone graft substitutes are frequently used to fill bone defects after orthopedic trauma. Ideally a synthetic bone graft substitute would have efficacy at least comparable to autograft, no immunogenicity, osteoinductive and osteoconductive properties, predictable resorption/degradation time, and no safety concerns. 

Numerous studies have reported benefits of using synthetic bone substitutes for fracture treatment and spinal surgery.4,5,6,7 These include reduced pain, bleeding and healing time, and improved functional outcomes compared with autografts. However, there have been safety concerns and problems with unpredictable resorption rates with some of the bone substitute materials.8

Furthermore, the different bone substitute products have varying characteristics. They all only provide minimal structural integrity and none targets all three of the key bone formation processes.9 Although some bone substitutes closely mimic the structure of natural bone, they lack osteogenic and osteoinductive properties. 

Bioactive glass has been successfully used in a range of tissue engineering procedures.3 With its versatility, achieved through the tailoring of properties through composition adjustments, its intrinsic strength and biocompatibility, bioactive glass was considered a prime candidate for improving synthetic bone substitutes.

Bioactive Glass for Bone Grafting

Introduction of bioactive glass into the body induces specific biological activity that causes soluble ionic species to be released. These lead to the glass becoming coated with a substance similar to hydroxyapatite. The formation of this layer allows bioactive glass to bond firmly with both hard and soft tissues. Furthermore, bioactive glass can be manufactured to release nutrients required for bone regeneration.

It has been shown that damaged bone regained its original strength more quickly when repaired using composite combined with bioactive glass compared with bone repair using composite alone and that the efficacy achieved is comparable to that of autologous bone grafting.10,11

A recent study compared spine fusion in rabbits using a mineralized collagen bone substitute with and without added bioactive glass. The bioactive glass-collagen composite was shown to closely mirror repair by autograft in terms of the amount and quality of the new bone.12 In addition, fusion occurred earlier when the collagen composite was augmented with bioactive glass.13

Conclusion

Bone grafting is an important tool for the repair of damaged or disease bone. The gold standard is autografting, which uses bone harvested from the patient to avoid rejection reactions. However, the increased morbidity caused by the additional surgery needed to acquire bone for grafting has resulted in an on-going quest to find an alternative. Bone substitutes have shown efficacy, but do not promote the formation of new bone. Bioactive glass is biocompatible and enhances strong new bone creation. Studies have now shown that the addition of bioactive glass to bone substitutes can increase their efficacy and bone healing characteristics to rival those achieved with autografting.

Mo-Sci produces medical implant grade bioactive glass in a form suitable for mixing with bone composites and can tailor its composition to meet specific requirements.13

References

1. Kinaci A, et al. Trends in Bone Graft Use in the United States. Orthopedics 2014;37(9):e783 e788.
2. Flierl MA, Outcomes and complication rates of different bone grafting modalities in long bone fracture nonunions: a retrospective cohort study in 182 patients. J Orthop Surg Res. 2013;8:33.
3. Rahaman MN, et al. Bioactive glass in tissue engineering. Acta Biomaterialia 2011;7:2355 2373.
4. Bajammal SS, et al. The use of calcium phosphate bone cement in fracture treatment: a meta-analysis of randomized trials. J Bone Joint Surg [Am] 2008;90-A:1186-1196.
5. Swiontkowski MF, et al. Recombinant human bone morphogenetic protein-2 in open tibial fractures: a subgroup analysis of data combined from two prospective randomized studies. J Bone Joint Surg [Am] 2006;88-A:1258 1265.
6. Lerner T, et al. A level-1 pilot study to evaluate of ultraporous beta-tricalcium phosphate as a graft extender in the posterior correction of adolescent idiopathic scoliosis. Eur Spine J 2009;18:170-9.
7. Dimar JR, et al. Clinical and radiographic analysis of an optimized rhBMP-2 formulation as an autograft replacement in posterolateral lumbar spine arthrodesis. J Bone Joint Surg [Am] 2009;91-A:137 186.
8. Carragee EJ, et al. A critical review of recombinant human bone morphogenetic protein-2 trials in spinal surgery: emerging safety concerns and lessons learned. Spine J 2011;11:471 191.
9. American Academy of Orthopaedic Surgeons. Bone-grafts: Facts Fictions and Applications. Presented at 70th Annual General Meeting. Louisiana 2003. Available at https://www.aaos.org/research/committee/biologic/bi_se_2003-1.pdf
10. Havener MB, et al. Improvements in Healing with a Bioactive Bone Graft Substitute in a Canine Metaphyseal Defect. Poster at 55th Annual Meeting of the Orthopaedic Research Society. February 22–25, 2009
11. Jia W, et al. Bioactive Glass for Large Bone Repair. Adv Health Mater. 2015;4(18):2842 2848.
12. Pugely AJ, et al. Influence of 45S5 Bioactive Glass in A Standard Calcium Phosphate Collagen Bone Graft Substitute on the Posterolateral Fusion of Rabbit Spine. Iowa Orthop J. 2017; 37: 193–198.
13. Mo Sci Corporation website. http://www.mo-sci.com/en/products

Firing different glass at the same time

Can I fire COE 90 and 96 in the same firing using the same schedule?

 In one sense this is the wrong question. The more general question is:

“Can I fire different glasses in the kiln at the same time?”

 Not all “CoE90” or “CoE 96” glass from different manufacturers have the same firing characteristics. This blog post compares the key temperatures for various glasses.

 For example, two glasses that are presumed to be “CoE90” have different published full fuse temperatures. Wissmach states its full fuse temperature is 777°C/1432°F and Bullseye states theirs is 804°C/1481°F. Both have an annealing temperature of 482°C/900°F.

 Wissmach 96 anneals at 482°C/900°F and Oceanside at 510°C/951°F. Wissmach96 has a full fuse temperature of 777°C/1432°F and Oceanside Compatible full fuses at 796°C/1466°F.

 Since annealing occurs over a range it is possible to anneal Wissmach96 and Oceanside Compatible together even though there is a published difference of annealing temperature of 28°C/50°F.  You could shotgun anneal – go very slowly from the soak at 510°C/951°F to 482°C/900°F with another soak.

 Fusing different manufacturers’ glasses – even if they are the same supposed CoE – is more difficult, unless you do not mind significantly different results.  Bullseye will full fuse at 804°C/1481°F. But Wissmach90 fuses at 777°C/1432°F. This will provide significantly different results.  The same for Oceanside and Wissmach96. The 21°C/38°F difference in full fuse temperature will provide lesser difference than the Bullseye Wissmach90, but will still be noticeable.

 This indicates that the full fuse effect of even the supposed same CoE will not be the same when fired together.

  

Finding the slumping temperature is determined less from the manufacturer than by observation. This post tells you how to find the slumping temperature.

 If these characteristics are similar, you can slump them at the same time. Expect some significant variation.

 There are some – possibly many – who will say firing different glass at the same time is both possible and successful. The manufacturers’ recommended temperatures show some wide variations. This makes it unlikely you will get the same desirable results for any but one of the glasses.

 My recommendation is do not try to fire different glass at the same time.  And why are you using two incompatible glasses anyway.

Getting Relevant People to Your Website

Credit: Visual Capitalist

Using your website to sell requires you to get relevant people to visit as a prerequisite.  But how can you get people to view your website?  And it needs to be relevant people - those who are potential buyers.

These are some suggestions on ways to attract visitors.

Keywords in the meta descriptions and in the text are important.  These are not just products, colours and other aspects of the work, although essential.  They are why people are buying.  Elements of this are buying gifts, e.g.:

• Holidays
• Celebrations
• Awareness days and weeks (Mother’s Day, birdwatch month, Gardening week, etc).

These need to be detailed in specific terms to bring people who are buying for birthdays, aniverseries, weddings, etc.

They may be buying for a purpose:

• Windows, 
• Kitchens,
• Decorative,
• Functional,
• Garden

Again, these need to be described in specific terms, e.g., splashbacks, dinner sets, wall art, etc.

Use the specific terms in your titles and early in the descriptions of each item.  This process is not easy, and you may want to enlist help from friends and family to get the right terms.  SEO is not the complete answer to getting visits, though.  There are other things you need to do

Categorise your pages with specific names rather than generic ones such as collection or portfolio. Use names such as splashback, tiles, birds, bowls, etc.  Leave the mention of glass to the description of each item. It doesn't really have a place in the title for your pieces.

Promote your social media and site at every opportunity. If you have been mentioned somewhere, let everyone know.  Use specific links to the work relevant to any communication within the post. All your printed material needs to have the addresses of your site and social media, also as part of the signature of your email address.  Link between all your social media platforms, your website and any selling sites you participate in.  

But it is not only your own site that you need to promote.  In promoting other sites that you are associated with, you spread the knowledge of what you do.  By linking and liking sites or businesses that have been useful to you, you may also get reciprocal mentions.  These all spread knowledge of what you do to a wider audience. 

Share

Make it easy for people to share the content of your site.  Have buttons and links that viewers can click on with no extra effort. Share links to other articles that you have found interesting.  The readers of those articles will pick up on your links.   Include internal links to other works on your website and any other selling platform in which you participate.

Update your website.

Updating the website is time away from making.  But it is essential to the selling of what you make.  Of course, you update your site every time you complete a piece of work - don't you?  You let people know of developments in your business life at they happen, surely.  This refreshing helps the indexing web crawlers to recognise a site that is current and so index the new stuff. By using all the specific terms in describing things, you will provide human browsers with the terms to direct them to you.

Respond to current matters

React to timely and trending topics.  These can be relevant general news items, upcoming events that are relevant to your potential customers, awareness days relevant to you and your work, etc.  What is happening in the craft world, or your section of it is of general interest.  It helps develop the audience for craft, which in turn, gives you a bigger audience.  Not everything needs to be about you. 

Write about your customers’ questions.  Give information about the questions and the background to them along with the response.  Use the customers’ language.  By doing this you are making use of the search terms used by your potential customers.  You don't get questions on your site?  There are other sources.  

• Keep track of the questions you are asked at craft and trade fairs and use them. 
• Use the questions you have of other crafts and craft workers, adjusted for your own work. 
• You can develop questions by googling for answers to your own questions and see how they are phrased.  Then use that kind of approach in outlining responses to the questions.

Use case studies in your updates and posts.  Providing in-depth descriptions of a commission or development of a product goes a long way to giving an insight to how you work and about your values.  These are interesting things for prospective buyers. And it engenders confidence in your approach to your work - your ethos.

Write for other sites that are relevant to your customers.  There are websites and blogs that publish guest articles.  You will need to develop a relevant pitch for each of the ones of interest.  Do only one pitch at a time to ensure you are not overwhelmed.

These suggestions are not exhaustive, of course.  It may seem like a lot of effort for uncertain results.  As you become practiced, you will find it easy to add a few paragraphs each day to one of your online presences.  These entries will provide the entry points for potential customers and develop the personality of your business.

Developing Bacteria-Resistant Tooth Fillings Using Bioactive Glass

 

Developing Bacteria-Resistant Tooth Fillings Using Bioactive Glass

Posted Krista Grayson on Jan 30, 2018

Photo by Lesly Juarez on Unsplash

Recently, with concerns over the potential toxicity of amalgam (silver fillings) and customer preference for less conspicuous fillings, there has been an increasing trend towards the use of composite (white fillings) materials for repairing dental decay. More than 122 million composite tooth restorations are made in the United States every year.2

Composite fillings are generally made from synthetic resins that are softer than natural tooth material, and so they are more susceptible to failure than amalgam (lasting 6-10 years versus several decades, respectively). However, all fillings will fail at some point as they crack or shrink away from the tooth. In both cases, the resultant gaps can harbor bacteria and food debris, increasing the risk of further tooth decay. The most common reason for replacement fillings is secondary caries occurring at the margins.

There has consequently been much research into developing a more durable filling material for the repair of dental decay, whilst still maintaining the aesthetic value.

Since bioactive glass is known to be biocompatible and is already used for many biomedical applications, its potential in dentistry has been explored. This article discusses the use of bioactive glass as a dental filling material. 

What is Bioactive Glass?

Glass does not elicit an immune response and so, by virtue of its high strength and low weight, has been widely used in a range of biomedical applications, including bone tissue engineering, bone regeneration and wound healing.4 Bioactive glass is a type of glass that is able to bond to either hard or soft tissue and also demonstrates antimicrobial activity. 

Bioactive glass is made from high purity raw materials, such as silicon oxide, calcium oxide, and phosphorus oxide, melted in platinum crucibles.5 They are available as discs, spheres, fibers and powders of varying sizes and with specific compositions.6 Furthermore, by modifying the composition and structure of the glass, its physical properties can be tailored to meet a specific need.5

Dental Bioactive Glass Composites

Following the success of bioactive glass in orthopaedic applications, bioactive glass was adopted for use in dentistry applications. It has shown substantial benefit in the repair of periodontal defects.4 

The observed antimicrobial activity alongside its demonstrated high strength made bioactive glass a prime candidate for tooth fillings. Fillings made with bioactive glass should slow secondary tooth decay by inhibiting bacterial colonization and increase the durability of composite filling materials. Furthermore, it was hypothesized that the bioactive glass may also provide minerals to strengthen the damaged surface of the tooth.

Evaluations of bioactive glass as a tooth filling have recently shown that such extrapolations to dentistry are indeed correct. Studies have demonstrated that the addition of bioactive glass to dental filling materials enhanced mineral formation in the dentin, promoting remineralization of dental caries7 and improved the mechanical properties of a filling in an aqueous environment.8 The latest research has shown that restorations made with a composite filling materials mixed with bioactive glass filler are significantly less prone to bacterial penetration.9 The proportion of the gap depth colonized with bacteria was 61% when a filler incorporating bioactive glass was used, compared with 100% for the conventional filler. 

Based on these findings the addition of bioactive glass to composite filling material may increase the durability of composite fillings while also reducing the incidence of secondary tooth decay at restoration margins.

Conclusion

Secondary decay at the site of tooth restorations is an ongoing challenge in dentistry. Tooth fillings that utilize bioactive glass composites have been shown to reduce bacterial colonization and strengthen composite fillings. This translates to a reduced rate of decay and increased lifetime of the restoration. The addition of bioactive glass to dental filler materials thus have the potential to offer patients requiring dental restorations a less problematic solution. 

Jamie Kruzic, a professor and expert in advanced structural and biomaterials in the Oregon State University College of Engineering, highlighted the benefits of incorporating bioactive glass into dental filling materials “This type of glass is only beginning to see use in dentistry, and our research shows it may be very promising for tooth fillings. The bacteria in the mouth that help cause cavities don’t seem to like this type of glass and are less likely to colonize on fillings that incorporate it. This could have a significant impact on the future of dentistry”.

References

1. National Institutes of Health. NIDCR Data & Statistics. Dental Caries (Tooth Decay) in Adults (Age 20 to 64). Available at: https://www.nidcr.nih.gov/DataStatistics/FindDataByTopic/DentalCaries/DentalCariesAdults20to64.htm
2. Stauth D. New study: Bioactive glass prolongs the life of tooth fillings Dentistry IQ, 5 January 2106. Available at http://www.dentistryiq.com/articles/2016/01/new-study-bioactive-glass-prolongs-the-life-of-tooth-fillings.html
3. Marks LAM, et al. Dyract versus Tytin class II restorations in primary molars: 36 months evaluation. Caries Research. 1999;33:387–392.
4. Rahaman MN, et al. Bioactive glass in tissue engineering. Acta Biomaterialia 2011;7:2355 2373.
5. Brauer DS. Bioactive Glasses—Structure and Properties. Angew Chem Int Ed 2015;54: 4160–4181.
6. Mo Sci Corporation website. http://www.mo-sci.com/en/products
7. Prabhakar AR, et al Comparative Evaluation of the Remineralizing Effects and Surface Micro hardness of Glass Ionomer Cements Containing Bioactive Glass (S53P4):An in vitro Study. Int J Clin Pediatr Dent. 2010 May-Aug;3(2):69-77. doi: 10.5005/jp-journals-10005-1057. Available at https://www.ncbi.nlm.nih.gov/pubmed/27507915.
8. Chatzistavrou X, et al. Fabrication and characterization of bioactive and antibacterial composites for dental applications. Acta Biomater.
9. 2014;10:3723–3732. Available at https://www.ncbi.nlm.nih.gov/pubmed/24050766
10. Khvostenko D, et al. Bioactive glass fillers reduce bacterial penetration into marginal gaps for composite restorations. Dental materials 2016;32(1):73–81. Available at http://www.demajournal.com/article/S0109-5641(15)00437-6/pdf

Trapped Glass

Glass can be trapped in or on moulds in various circumstances. These usually relate to the relative expansion and contraction characteristics of the glass and mould.  The two materials most usually concerned are steel and ceramic.

Releasing glass from steel

Frequently when using steel as dams around glass, the glass becomes stuck inside the steel.  The cause of this is the greater contraction of the steel than the glass.  On cooling, the steel compresses the glass tightly. 

Another circumstance where glass is trapped is while slumping glass into a steel vessel.  If the draft of the sides of the vessel is steep, the glass cannot slip upwards as the steel contracts against the glass, so trapping the glass.

Most successful attempts to remove the glass from the steel are like removing a metal lid from a glass jar.  Heat the metal and try to keep the glass cool.  You can run hot water on the steel while keeping the glass cool.  This will most often allow the glass to be pulled from the steel surround, assuming there was a glass separator applied to the steel.

Putting the whole assembly in the freezer will only increase the grip of the steel as it will contract even more than the glass.

Prevention of trapping the glass involves placing a cushion between the steel and glass.  This is usually 3mm fibre paper.  Sometimes this has a layer of Thinfire added to give a smoother edge to the glass.  Other times, the fibre paper is coated with boron nitride.  There is no need to use both Thinfire and boron nitride, of course.

Releasing glass from ceramic

The difficulty of glass trapping ceramic occurs during draping.  Ceramic expands and contracts less than glass.  This means that the glass will trap a kiln washed ceramic shape with a steep draft.  The glass on cooling, contracts more than the ceramic which means the glass is tightly encasing the ceramic. 

A ceramic draping mould from which  it may be difficult to remove the glass.

Most successful attempts to remove the glass from the ceramic form include either gently warming the glass or freezing the whole assembly.  You could place the glass in a bath of warm water.  This encourages the glass to expand, but does not heat the ceramic.  This usually provides enough gap to ease the glass from the ceramic form.

The other approach is to put the whole into the freezer.  This is utilising the greater contraction of the ceramic to release the glass. This is less immediate than the warming of the glass, of course.

Prevention of trapping glass on ceramic with shallow drafts involves covering the form with 3mm fibre paper to provide a cushion during the contraction.  The fibre paper may need to be attached to the form by binding with high temperature wire, as glues will not survive the heat of draping.

Further information is available in the ebook: Low Temperature Kiln Forming.

Using Bioactive Glass to Encourage Implant Fixation

 

Using Bioactive Glass to Encourage Implant Fixation

Posted Krista Grayson on Jan 5, 2018

Bioactive glass induces specific biological activity when implanted in the body that causes the glass to become covered with a substance similar to hydroxyapatite. The formation of this layer allows bioactive glass to bond firmly with both hard and soft tissues.

This behavior has instigated extensive research into the use of bioactive glass to facilitate the repair of damaged bone. Furthermore, these bioactive glasses are biocompatible, and so do not elicit immune responses that can lead to rejection of foreign materials introduced into the human body.

Although brittle, bioactive glass offers a strong, yet lightweight, biodegradable framework to support healing. Furthermore, new borate and borosilicate bioactive glasses have been shown to enhance bone regeneration. In addition, the composition of bioactive glass can be adjusted to determine how long it persists in the body before it degrades so it provides support as long as is needed.1

Considerable success has been achieved using bioactive glass in the repair of bone, soft tissue and cartilage.1 Bioactive glass has also been shown to be beneficial in periodontal reconstruction2 and to promote the healing of ulcers in patients at risk of leg amputation.3

The efficacy of bioactive glass in enhancing the healing of both hard and soft tissues led to investigation into their application in reconstructive surgery requiring the use of permanent implants. This article explores how bioactive glass can help encourage the integration of implants.

Ensuring that Implants are Biocompatible

The human body has an amazing capacity to heal itself. However, in the case of multiple or complex fractures or serious infection or disease there can be too much of the original bone missing for it to heal satisfactorily. In such cases a bone graft or scaffold is required to support regeneration or bone fusion. Similarly implanted devices, such as plates, or screws and joint replacements, may be needed to reinforce or replace weak or damaged bones and joints. Similarly, implants may be required in dentistry to facilitate artificial replacement of a tooth root. These are usually in the form of a metallic screw positioned in the jaw bone that can support one or more false teeth.

Bone taken from another part of the patient’s body, an autograft, is the preferred implant for bone repair since it will not be at risk of rejection. However, this can be hampered by availability or suitability and incurs additional morbidity for the patient at the site from which the graft is harvested.

Titanium alloy implants have good biological compatibility but, in order for the implant to provide a strong structural support, it must be integrated into the bone (osseointegration) and it can take several months for the bone to grow in and/or around the implant. The implant must also be mechanically and morphologically compatible so it maintains good contact with the recipient bone to promote bony cell growth. In addition, there is the risk of metal implants being corroded by body fluids and releasing potentially toxic products.

Consequently, there has been much research into coatings for prosthetic metallic implants.4

Coating Implants in Bioactive Glass

Bioactive glass is one such coating material that is currently the focus of much research. Once in the body, an amorphous calcium phosphate layer forms on the surface of bioactive glass. Within hours, this layer incorporates blood proteins and collagen and crystallizes into hydroxycarbonate apatite. This layer is now very similar to natural bone mineral, and so bonds readily to the recipient tissues/bone. Bioactive glass is therefore a prime candidate for coating implants that need to become integrated into bone.

Including bioactive glass in polymeric scaffolding materials has been shown to accelerate the formation of a strong bond between the scaffold and tissue and promote healing.5 It followed that similar technologies may facilitate the osseointegration of the implants.

Numerous technical challenges have been overcome and titanium implants have been successfully coated with bioactive glass4 and evaluations of bioactive glass-coated implants have had promising results.6,7,8 Bioactive glass coatings on both orthopaedic and dental implants were shown not induce any adverse effects or inflammatory response in the surrounding tissue6. Furthermore, bioactive glass coatings accelerated cell attachment, spreading, proliferation, differentiation, and mineralization of the extracellular matrix and promoted rapid bone growth.6,7 In addition, the proportion of bone-to-implant contact were significantly greater for implants coated with bioactive glass.8

Bioactive glass can be obtained in a range of sizes and compositions9 suited to a range of applications. Indeed, bioactive glass can be custom made to specifications that precisely match a specific need, in terms of strength, degradation rate etc. 

Conclusion

Implants are commonly needed in orthopaedic surgery to facilitate the repair of damaged or missing bone and in dental reconstructions. Although implants have been used with great success, procedures may be limited by rejection issues and toxicity concerns. Furthermore, it can take several months for an implant to become integrated into the recipient bone and this increases the risk of failure and prolongs recovery times.

The biocompatibility and strength of bioactive glass along with its ability to promote tissue regeneration has made it an invaluable tool in tissue engineering. With recent technological advances, it is now possible to coat metal implants with bioactive glass. Implants coated in this way have demonstrated great advantages in terms of both patient safety and recovery. The bioactive glass coating protects the metal implant from corrosion by bodily fluids thereby minimizing the risk of potentially toxic products entering the body. It also promotes new bone growth so the implant becomes secured in the bone more rapidly.

Bioactive glass coatings on implants can be used to encourage implant fixation, improve healing rates and maximize implant effectiveness.

Mo-Sci produce high quality bioactive glass in a form suitable for coating implants and can tailor its composition to meet specific requirements. 

References 

1. Rahaman MN, et al. Bioactive glass in tissue engineering. Acta Biomaterialia 2011;7:2355 2373.
2. Sohrabi K, et al. An evaluation of bioactive glass in the treatment of periodontal defects: a meta-analysis of randomized controlled clinical trials. J Periodontol 2012; 83: 453 464.
3. The American Ceramic Society Press release 4 May 2011. Available at https://www.sciencedaily.com/releases/2011/05/110503133056.htm
4. Lopez-Esteban S, et al. Bioactive glass coatings for orthopedic metallic implants. Journal of the European Ceramic Society 2003;23:2921–2930.
5. Lu HH, et al. Three-dimensional, bioactive, biodegradable, polymer-bioactive glass composite scaffolds with improved mechanical properties support collagen synthesis and mineralization of human osteoblast-like cells in vitro. J Biomed Mater Res 2003;64A:465–474.
6. Mehdikhani-Nahrkhalaji M, et al. Biodegradable nanocomposite coatings accelerate bone healing: In vivo evaluation. Dent Res J (Isfahan). 2015;12(1):89 99.
7. Chen Q, et al.Cellulose Nanocrystals–Bioactive Glass Hybrid Coating as Bone Substitutes by Electrophoretic Co-deposition: In Situ Control of Mineralization of Bioactive Glass and Enhancement of Osteoblastic Performance. ACS Appl Mater Interfaces. 2015 Nov 11;7(44):24715 25.
8. van Oirschot BA, et al. Comparison of different surface modifications for titanium implants installed into the goat iliac crest. Clin Oral Implants Res. 2016;27(2):e57 67.
9. Mo Sci Corporation website. http://www.mo-sci.com/en/products

Tack Fusing Difficulties

Many novice kilnformers tend toward the use of tack rather than full fusing in their work.  This is a bit perplexing, as tack fusing is more difficult than full fusing to complete successfully.

Why is tack fusing more difficult? 

The single most important reason is that the pieces of glass on top of the base shade the heat from the area underneath. And they do that unevenly over the base glass. Additionally, the tacked pieces are not fully incorporated into the base and so tend to behave as separate pieces, especially on angular tack fusing.  Both these factors require greater thought and care in scheduling.

Evidence

The evidence for the statement that tack fusing is more difficult than full comes from several areas.

There is a lot of evidence on social media of failed tack fused projects.  It may be argued that it is natural for the difficulties to be highlighted on the self-help groups. And the successes are not so widely shared.  There are other pieces of evidence.

Breaks of base sheet while the overlaying pieces remain intact.  

 This is a result of the overlaying glass shading the heat from the lower layers.  Some writers describe the effect as glass “seeing” heat.  The glass reacts more quickly to radiant heat than to transmitted heat from the air.  As a result, the glass exposed to the radiant heat absorbs heat more easily than the shaded areas.  This leads to uneven heating during the rise in temperature and a build-up of stress which frequently causes breaks from expansion differences in the base glass.

Breaks along the borders of the thick and thin areas of pieces are common in tack fusing.  

 This usually occurs during the cooling.  Thick and thin areas take different amounts of time to release the stored heat.  As in heat up, if the temperature differential is too great, the glass will break.  Research by Bullseye has shown that significant stress can be built up by temperature differences greater than 5°C across the piece.  What temperature difference is required to develop enough stress to cause a piece to break is unknown, although it does relate to the degree of variation in thicknesses and areas of base covered.

Scheduling as for thicker pieces.

 Further evidence is given by several sources stating that tack fusing projects need to be scheduled as though between 1.5 and 2.5 times the actual thickness to be successful.  This need for more careful firing is supported by the success of this strategy which increases the heat work as applied to tack fusing.

Further information is available in the ebook Low Temperature Kiln Forming.

Tack fusing requires more care than flat fusing because of heat shading and thickness differences.  There are some scheduling approaches that can minimise the risks of breakage.

Encouraging Vascular Regeneration using Bioactive Glass Microfibers

Encouraging Vascular Regeneration using Bioactive Glass Microfibers

Posted Krista Grayson on Dec 4, 2017

Developments in tissue engineering over recent years have made possible the restoration of serious trauma.1 Using temporary scaffolds of biologically compatible substitutes, such as bioengineered tissue, damaged, injured or missing body tissues can be replaced.

With significant advances in the available scaffolds for use in tissue engineering, the provision of an adequate blood vessel system — vascularization — has become the key limitation to the regeneration of tissues after trauma.2

Several approaches have been used to achieve the necessary vascularization to supply sufficient blood to bioengineered tissue. These include loading the scaffold with angiogenic growth factors, such as vascular endothelial cell growth factor (VEGF), or endothelial cells and even prevascularization of the tissue to be implanted.2

Bioactive glasses have been shown to provide effective scaffolds for soft tissue engineering.1 They are biocompatible, lightweight and strong, and can be produced to degrade at a rate that matches the growth of new tissue.1 More recently, it has become apparent that bioactive glass also promotes angiogenesis that is important for supporting new tissue growth.

The Need for Tissue Engineering After Trauma

The human body has a remarkable ability to heal itself after undergoing trauma. However, such healing is a complex biological process requiring many different cell types to complete the necessary steps at the right time.3 If large amounts of tissue have been lost, tissue engineering is used to provide a temporary biomaterial scaffold to provide the necessary support or shape while the new tissue grows.

Initially, damaged blood vessels must constrict to stem blood loss but then they are required to regenerate to provide nutrients to the new tissue created to restore the damage. Vascular regeneration is thus an important step in the healing process. If there is not an adequate vascular system, the nutrients required for growth cannot be supplied.

Bioactive glass, by virtue of its biocompatibility, strength and range of achievable properties, is widely used to provide support in tissue engineering and been used with much success in the repair of bone, soft tissue and cartilage repair.1 Once implanted in the body, reactions occur on the surface of bioactive glass that facilitate bonding with existing tissue. Furthermore, bioactive glass can release ions, such as calcium that is important for regeneration of skin and bone, that are needed to support regeneration and promote rapid bone formation.4

More recently it has also become apparent that bioactive glass can promote vascularization without the need for adding growth factors to the scaffold.5-7 

Bioactive Glass can Accelerate Healing

Bioactive glass is a valuable tool in tissue engineering. Although originally used to facilitate bone repair, it has also provided tremendous benefit when included as a component of bioscaffold materials used in soft tissue repair. Bioactive glass has been shown to speed up healing and has the added benefit that its rate of resorption can be tailored to meet a particular repair need.1

A novel form of borate bioactive glass has been successfully used in wound healing.8 A fibrous network of calcium-rich glass fibers forms a scaffold to promote skin regeneration. When this bioactive glass was used in patients with diabetic ulcers who were at risk of limb amputation, the skin was fully repaired in almost two thirds of cases after a few months with little if any scarring.8

More recently, it has been shown that bioactive glass actively enhances tissue regeneration by stimulating the secretion of angiogenic growth factors that promote the proliferation of microvascular endothelial cells and enhance revascularization.5,6 Thus, bioactive glass is able to augment a critical process in tissue regeneration.7 This allows more rapid tissue repair without the need for adding recombinant inductive growth factors.

Conclusion

Bioactive glass is established as a key tool in a range of tissue engineering applications. It promotes the repair of bone and soft tissue whilst providing structural support. Furthermore, the bioactive glass can be designed to last just as long as is needed for the new tissue to gain the necessary volume and strength for the repair to be completed.

In addition, it has been shown that bioactive glass also increases the levels of angiogenic growth factor, which accelerate vascular regeneration. Vascularization is a key process in tissue repair since blood vessels are required to provide the nutrient for new tissue to develop and grow. Previously, recombinant growth factors were added to tissue engineering scaffolds to promote the creation of new blood vessels. This extra process can now be obviated by including bioactive glass as a component of the scaffold material.

Proangiogenic potential is thus another desirable quality that can be added to the properties of bioactive glass. This further supports the use of bioactive glass in temporary healing scaffolds during tissue engineering procedures.

Mo-Sci produces medical implant grade bioactive glass in a range of formats suitable for use in a wide variety of tissue engineering scaffolds and can tailor its composition to meet specific requirements.9 

References

1. Rahaman MN, Day DE, Bal S, et al. Bioactive glass in tissue engineering. Acta Biomaterialia 2011;7:2355 2373.
2. Baiguera S and Ribatti D. Endothelialization approaches for viable engineered tissues. Angiogenesis. 2013 Jan;16(1):1 14.
3. Guo S, and DiPietro LA. Factors Affecting Wound Healing. J Dent Res. 2010;89(3): 219–229.
4. Gerhardt L-C and Boccaccini AR. Bioactive Glass and Glass-Ceramic Scaffolds for Bone Tissue Engineering. Materials 2010;3:3867 3910.
5. Day RM, et al. Bioactive glass stimulates the secretion of angiogenic growth factors and angiogenesis in vitro. Tissue Eng. 2005 May-Jun;11(5-6):768 77.
6. Leu A and Leach JK. Proangiogenic Potential of a Collagen/Bioactive Glass Substrate. Pharmaceutical Research 2008;25 (5):1222–1229.
7. Gorustovich A, et al. Effect of bioactive glasses on angiogenesis: In-vitro and in-vivo evidence: A review. Tissue Eng. Part B Rev. 2010;16:199 207.
8. The American Ceramic Society Press release 4 May 2011. Available at https://www.sciencedaily.com/releases/2011/05/110503133056.htm
9. Mo Sci Corporation website. http://www.mo-sci.com/

 

Fusing slumped pieces together

I have a plate I made using this mold. It’s 6”x6”. … [it is broken into] 8 large pieces. Is it possible to piece it together into the mold and full fuse the plate again in the mold? … Or do I need to try to piece it together on the shelf paper and full fuse and hope for the best?

Full fusing in the mould is unlikely to be satisfactory.  The glass at full fuse will move toward the bottom of the mould, making a thick puddle. Alternatively, it will form a large thick bubble at the bottom, as I see no vent holes in the corners at the base of the mould.  It will also have significant marking from dragging along the mould and from the mould texture.  It also presents some risks to shorten the life of the mould.

Fusing a dropped and broken piece that has been slumped is unlikely to be successful, whether fused in the mould or fused flat first.