Biomedical Engineering Reference
In-Depth Information
can also colonise on the surface of dental implants and cause bone
loss, which can lead to loosening of the implant. Certain bioactive
glasses have shown antimicrobial effects. The dissolution of the glasses
in body fluids leads to an interfacial environment that prevents the
attachment and growth of microorganisms. As bioactive glasses enhance
bone regeneration and inhibit growth of various microorganisms, they
have great potential in dental applications.
The tissue bonding of bioactive silicate glasses can be related to their
ability to form HCA layers on their surfaces in body fluids [1]. The HCA
is critical for tissue bonding - when the layer is formed, the biological
mechanisms of bonding will start. Ideally, the new tissue is remodelled
at a rate equal to that at which the glass dissolves.
In the mid-1980s, a systematic investigation of glasses suitable for
use as bioactive coatings on metal prostheses was started [2]. One of
the glasses, S53P4 glass, was adapted for further studies in the field
of bone regeneration applications. Two glasses, 45S5 glass (Bioglass
®
)
and S53P4 glass (BonAlive
®
), are approved by the US Food and Drug
Administration (FDA) for certain clinical applications. The oxide com-
positions of the melt-derived glasses 45S5 and S53P4 are presented in
Table 11.1.
Both glasses are available as particulates for repair of bone defects in
dental applications. Bioglass is sold as PerioGlas
®
(NovaBone Products
LLC, Alachua, Florida). Over the years, several studies of the
in vitro
and
in vivo
properties and the clinical applications of 45S5 and S53P4
glasses have been performed. However, both glasses have been tested
simultaneously only in very few studies. Generally, 45S5 glass reacts
more rapidly than S53P4, which is also suggested by the respective silica
contents of the glasses. When cones were implanted in rat femur and
soft tissue, HCA layers formed on both glasses [3]. In all implantation
tests, the layer thicknesses were slightly higher for 45S5 than for S53P4.
Scanning electron micrographs of the cross-sections of 45S5 and S53P4
cones after eight weeks in femur are shown in Figure 11.2. The images
were taken after a push-out test of the cones. Both glasses showed
Table 11.1
Oxide compositions of 45S5 glass and S53P4 glass, in mol% (wt%).
Glass
SiO
2
Na
2
O
CaO
P
2
O
5
45S5
46.1 (45)
24.4 (24.5)
26.9 (24.5)
2.6 (6)
S53P4
53.8 (53)
22.7 (23)
21.8 (20)
1.7 (4)
