Biomedical Engineering Reference
In-Depth Information
melt-quenched and one sol-gel derived glasses. All glasses showed a
growth-inhibiting effect, but the bacteria culture time and concentration
of glass needed varied with glass composition and bacterial type. The
antibacterial effect correlated with both the pH of the solution and the
concentration of the alkali ions dissolved from the glasses. In both series,
S53P4 glass was found to be the most effective in killing the bacteria. The
mechanism of the antibacterial effect of bioactive glasses is not properly
understood. However, the observations clearly indicate the potential of
bioactive glasses in preventing and treating bacteria-induced infections.
11.8 BIOACTIVE GLASSES IN POLYMER COMPOSITES
Biostable synthetic polymers are used in restorative dentistry. The adhe-
sion and bonding between the dental restoration and the biological
tissue are crucial for satisfactory performance. Mixing with glass parti-
cles to produce polymer composites offers a feasible method to enhance
the osteointegration of the implant. Chapter 9 discussed composites
in detail.
The use of fibre-reinforced composites (FRCs) in dental prosthetic
devices is steadily increasing. One novel application studied was the
replacement of the currently used cylindrical screw-like pure titanium
or titanium alloy oral implants with FRC implants. The mismatch of
the elastic properties between the metal and the bone might lead to
failure of the implant. The use of FRC implants has been motivated
by the possibility to tailor the elastic modulus to values close to that
of the bone. The FRC implants, fabricated of light-curing E-glass-fibre
dimethacrylate composite, were coated with S53P4 glass particles to
improve the osteointegration. According to push-out testing from dental
plaster, the threaded FRC cones coated with glass particles successfully
withstood static load values comparable to human bite forces without
fracture [20]. The push-out force was higher for the threaded FRC
implants with bioactive glass coating than for the titanium implants.
The method for the manufacture of the implant was found to affect the
tissue response
in vivo
.
The utilisation of bioresorbable polymers in dental and orthopaedic
applications has arisen from the biological ability of the bone tissue to
self-repair. Biodegradable polymers can provide temporary mechanical
support to the healing tissue and ideally the polymer dissolves at the
same rate as the new tissue is regenerated. The most important synthetic
bioabsorbable polymers studied for clinical uses are polyglycolide (PGA),
polylactides (PLAs), poly(lactic-
co
-glycolide) (PLGA), polycaprolactone
