Biomedical Engineering Reference
In-Depth Information
Nanotechnology offers a new strategy to develop bioactive glasses with a higher surface area.
Nanotechnology is defined as a science that involves the development of materials and devices at
the nanoscale. Specific properties of bioactive glasses can be improved and controlled when synthe-
sized in nanometer scale. Therefore, nanosized biomaterials have greater biocompatibility and bio-
activity. This new approach is important both for bioactive glasses used in particulate form as well
as for coatings on biomedical devices or as fillers in composite materials.
Over time, bioactive glasses have been applied in various specialties of dentistry such as
periodontics, endodontics, and implantology. This chapter describes the importance and applica-
tions of bioactive glass in dentistry and periodontics.
15.2
Composition and synthesis of bioactive glass nanoparticles
Bioactive glass when in contact with body fluids induces a specific biological response at the inter-
face of the material, resulting in the formation of a carbonated hydroxyapatite (HA) layer on its
surface and, through this layer, binding to the mineralized tissue. The bioactivity of bioactive glass
is not an absolute concept determined only by the composition but is also affected by the size and
shape of the material. The formation of this HA layer is essential for synthetic materials to exhibit
bioactivity
[3,4]
.
There is an advance in research on bioactive glasses for newer applications in tissue engineer-
ing, and therefore new routes of synthesis of bioactive glass have been proposed. A high surface
area silica-rich is crucial for the formation of HA layer. Sol
gel glasses exhibited increasing spe-
cific surface area and pore volume compared with the glasses produced by conventional melting
process, which enhanced their biocompatibility and bioactivity by accelerating the deposition pro-
cess of HA
[3,4]
. One approach to improve the properties of bioactive glass material is their devel-
opment at the nanoscale. Reducing the size of bioactive glass granules can accelerate the formation
of HA layer and also provide more active sites for cell attachment. Compared with microparticles,
nanoparticles have significantly higher surface area, and this drastically changes the material char-
acteristics such as surface energy, wettability, surface topography, and surface chemistry.
Furthermore, studies have shown that nanoscale materials have higher biocompatibility
[5,6]
.
Ostomel et al. (2006) also showed that the reduction of bioactive glass particles to nanoscale could
stimulate their bioactivity
[7]
. Bioactive glasses are capable of forming a HA layer, and the
osseointegration to bone tissue is performed through this layer. The rate of osseointegration to the
mineralized tissue depends on the rate of formation of HA layer, which depends on the composition
of the bioactive glass
[4,8]
.
The basic components of most bioactive glasses are SiO
2
,Na
2
O, CaO, and P
2
O
5
. However,
among the sol-gel-derived bioactive glasses, the composition of 60% SiO
2
, 36% CaO, and 4%
P
2
O
5
(by weight) has a high level of bioactivity, showing great potential for engineering applica-
tions of mineralized tissues
[9]
. In the past decade, several studies have been directed at the devel-
opment of bioactive glass nanoparticles. Recently, Brunner et al. (2006) reported on the preparation
of bioactive glass nanopowders using flame synthesis, a process that requires a high-temperature
environment
[10]
. By contrast, sol-gel technology is a low-temperature preparation method, and
the glasses prepared by the sol-gel method contain a porous structure with a higher surface area.
