Encouraging Bone Defect Repair with Bioactive Glass

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Although autologous bone is the gold standard for filling bone defects, the additional morbidity involved for the patient in harvesting bone for grafting has led to a growing preference for alternative techniques. The need for additional surgery to obtain the bone is eliminated by using donated bone, but such allografts always carry the risk of an immune response which prevents them from being accepted.

As a result, the use of synthetic bone graft materials is increasingly gaining recognition.¹ Various bone graft substitutes have been used in the quest to find an alternative to bone that provides a strong and rapid repair. These include bone morphogenetic proteins, collagen- and hydroxyapatite-based substitutes, calcium phosphates, and demineralized bone matrix.

Calcium Phosphates for Synthetic Bone Grafts

Since calcium phosphate ceramics are very similar to the mineral components naturally present in bone tissue, they represent a prospective alternative for a synthetic bone filling material. Owing to their ready availability and biocompatibility, calcium phosphate ceramics are being extensively used an alternative to autografts and allografts.

Calcium phosphates have demonstrated good cell attachment when used as tissue engineering scaffolds and bone substitutes. They are also known to provide predictable outcomes and lower morbidity for the patient whilst being more economical than traditional bone grafts.^2,3

To begin with, calcium phosphate ceramics were not porous enough to enable immediate bone ingrowth and rapid integration into the bone tissue. However, modifications in the parameters used during the preparation of calcium phosphates have resulted in the production of products with superior chemical and physical characteristics, such as porosity and specific surface areas.

Careful selection of the precise combination of properties has aided the development of bone filling materials that enhance the adhesion, proliferation, and differentiation of cells, thus enabling enhanced osteoconductivity.⁴

Calcium Phosphate Bioactive Glasses

Calcium phosphate bioactive glass is an especially preferable form of synthetic bonegraft as it is antimicrobial, bioactive, and osteoconductive. Furthermore, minerals, such as calcium, are released from the bioactive glass providing critical substrates for the production of new bone.

When implanted in the body, bioactive glasses stimulate specific biological activity that results in the formation of an amorphous calcium phosphate layer on its surface. Over a few hours, this layer incorporates collagen and blood proteins and crystallizes into hydroxycarbonate apatite, which makes it relatively similar to natural bone mineral. Hence, bioactive glass bonds readily to the recipient bone.

In addition, the properties of bioactive glass, such as rate of reabsorption and particle size, can be customized by adjusting the exact composition to meet the needs of a specific repair procedure.^4,5

Bioactive Glasses Encourage Bone Repair

Bioactive glass has been effectively used in an array of tissue engineering procedures.³ With its versatility, attained by customizing the properties, its intrinsic strength and biocompatibility, bioactive glass holds many of the features required in a synthetic bone substitute.

Bioactive glass bone filler composites have also been filled with growth factors, proteins, and drugs to facilitate repair by directly delivering the therapeutic agents into the defect region.⁷

It has been demonstrated that damaged bone regained its original strength more rapidly when repaired using a composite bone filler material that contained bioactive glass compared to bone repair using composite alone. Moreover, when bioactive glass is included to the bone substitute, the efficacy realized is equivalent to that achieved with the autologous bone grafting, which is the gold standard. Recently, a bioactive glass synthetic bone substitute was shown to be effective in the repair of cavitary bone defects in patients with chronic osteomyelitis.⁸

Bioactive glass has also demonstrated great potential in various other orthopedic applications including the strengthening of bone at the site of joint replacements, plates, or screws, and spinal fusion and the coating of implants. Bioactive glass coatings on orthopedic implants did not cause any unfavorable effects or inflammatory response in the surrounding tissue.⁹ Additionally, bioactive glass coatings expedited cell attachment, differentiation, proliferation, spreading, and mineralization of the extracellular matrix and encouraged rapid bone growth. Spine fusion carried out in rabbits using a mineralized collagen bone substitute with and without added bioactive glass showed that when bioactive glass is added, it resulted in earlier fusion of the bone. Moreover, the addition of bioactive glass attained a repair comparable to that seen with autograft in terms of the quality and amount of the new bone.¹⁰

Mo-Sci manufactures high implant grate bioactive glass in various forms suitable for a variety of bone repair applications, and can customize its composition to meet specific demands.⁵ It is possible to adjust the composition and form of the bioactive glass to match the patient’s intrinsic conditions as well as the rate and pattern of bone formation required.⁴

References and Further Reading

1. Kinaci A, et al. Trends in Bone Graft Use in the United States. Orthopedics 2014;37(9):e783 e788.
2. Saffar JL, et al. Bone formation in tricalcium phosphate-filled periodontal intrabony lesions. Histological observations in humans. J Periodontol 1990;61(4):209–216.
3. Barrère F, et al. Bone regeneration: Molecular and cellular interactions with calcium phosphate ceramics. Int. J. Nanomed. 2006, 1, 317–332.
4. Lobo SE, et al. Biphasic Calcium Phosphate Ceramics for Bone Regeneration and Tissue .Engineering Applications. Materials 2010;3:815-826.
5. Mo Sci website. https://www.mo-sci.com/en/products
6. Jia W, et al. Bioactive Glass for Large Bone Repair. Adv Health Mater. 2015;4(18):2842 2848.
7. Schumacher M, et al. Calcium phosphate bone cement/mesoporous bioactive glass composites for controlled growth factor delivery. Biomater. Sci. 2017;5:578 588.
8. Ferrando A, et al. Treatment of Cavitary Bone Defects in Chronic Osteomyelitis: Biogactive glass S53P4 vs. Calcium Sulphate Antibiotic Beads. Bone Jt Infect. 2017;2(4):194 201.
9. Mehdikhani-Nahrkhalaji M, et al. Biodegradable nanocomposite coatings accelerate bone healing: In vivo evaluation. Dent Res J (Isfahan). 2015;12(1):89 99.
10. 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.

About Mo-Sci

Mo-Sci, a world leader in precision glass technology, explores and develops new and exciting ways for their products and services to integrate within a wide variety of useful applications.

Mo-Sci has become a world leader in the research, development and manufacturing of glasses for specialty applications.

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