Development and Applications of Varieties of Bioactive Glass Compositions in Dental Surgery, Third Generation Tissue Engineering, Orthopaedic Surgery and as Drug Delivery System

Bioactive glass is composed mainly of silica, sodium oxide, calcium oxide and phosphates. The bone-bonding reaction results from a series of reactions in the glass and its surface (Hench & Wilson, 1984). When granules of bioactive glass are inserted into bone defects, ions are released in body fluids and precipitate into a bone-like apatite on the surface, promoting the adhesion and proliferation of osteogenic cells (Ohtsuki et al., 1991; Neo et al., 1993) which is partially replaced by bone after long time implantation (Neo et al., 1994). The ion leaching phenomenon involves the exchange of monovalent cations from the glass, such as Na+ or K+, with H3O+ from the solution, and thus causes an increase in the pH of the solution. It is known that osteoblasts prefer a slightly alkaline medium (Ramp et al., 1994; Kaysinger & Ramp, 1998), but it is also known that severe changes in pH can inhibit osteoblast activity and cause cell necrosis or apoptosis (Brandao-burch et al., 2005; Frick et al., 1997; El-ghannam et al., 1997). Bioactive glass with a macroporous structure has the properties of large surface areas, which are favourable for bone integration. The behaviour of bioactive glass is dependent on the composition of the glass (Brink, 1997; Brink et al., 1997), the surrounding pH, the temperature, and the surface layers on the glass (Andersson et al., 1988; Gatti & Zaffe, 1991). The porosity provides a scaffold on which newly-formed bone can be deposited after vascular in growth and osteoblast differentiation. The porosity of bioglass is also beneficial for resorption and bioactivity (De Aza et al., 2003). In push-out tests the strength of the chemical bond between bioactive glass and the host tissue has been measured to be at least ten times higher than the contact osteogenesis (Anderson et al., 1992). Its high modulus and brittle nature makes its applications limited, but it has been used in combination with poly-methylmethacrylate to form bioactive bone cement and with metal implants as a coating to form a calcium-deficient carbonated calcium phosphate layer. Certain bioactive glass are strong enough to function in stress-bearing sites in the head and