Biomedical Engineering Reference
In-Depth Information
complications in orthopedic surgery, and the problem usually leads to
removal of the implant [66]. The artifi cial implants in the body obstruct
the host defence mechanism and win over the dose of antibiotics
[66- 68]. Therefore, a high dose of antibiotics is crucial to avoid such
prosthetic infections, but higher concentration of antibiotics enhances
side effects in body [66]. Hence, it is preferable that the implant itself
have antibacterial properties to reduce the chances of infections.
7.2.5.1 Glass
−
Ceramics
Many studies have reported the response of interaction of bioactive
ceramics with microorganisms [69]. The studies showed that micro-
bial
induced degradation occurred
in vitro
and the presence of bacte-
ria increases the levels of calcium in the growth media [66]. Infection is
harmful for the host as well as for the implant itself [63]. Proteins of the
growth medium are easily absorbed on the HA surface, resulting in a
suitable environment for bacterial adsorption and proliferation [70]. The
silver particles with HA coating were also found to exhibit admirable
antimicrobial property. Silver is a ductile metal, so when it is reinforced
in brittle HA matrix, it stops the crack propagation by crack
−
bridging
mechanism. Silver reinforcement shows the elastoplastic stretching
along the crack wake, thereby increasing the toughness and strength of
composites [69]. Therefore, metallic (Ag/Ti, etc.) or ceramic (Al
2
O
3
, ZrO
2
,
mullite, etc.) particulates are commonly incorporated in HA matrix. In
addition to the potential for improvement in mechanical properties,
silver provides advantageous biochemical inertness and an antibacterial
effect [69, 71].
Kalmodia
et al.
reported the
in vitro
cellular and antimicrobial response
of SiO
2
-MgO-Al
2
O
3
−
−
K
2
O-B
2
O
3
-F glass ceramics (GC) having fl uorophlog-
opite crystalline phase as a major constituent. Fluorine and boron content
in base glass affects the cytocompatibility and antibacterial property. The
cellular morphology of mouse fi broblast L929 cells shown in Figure 7.11
exhibit cytocompatibility of GC substrate. In this work it is also reported
that lower fl uorin content in GC enhances the osteoconduction and viabil-
ity of eukaryotic cells [72]. The mechanical properties obtained with SiO
2
-
MgO-Al
2
O
3
−
K
2
O-B
2
O
3
-F glass ceramic are summarized in Table 7.1.
It is found that a specifi c glass ceramic composition exhibits good anti-
microbial property for both gram positive and gram negative bacteria.
Also, the glass ceramic, with higher fl uorine content has less quantifi ed
antimicrobial property (84% CFU/ml in M3 vs 77% CFU/ml in M2). It
appears that a higher amount of SiO
2
in glass ceramic suppresses the bene-
fi cial effect of F
−
as far as bactericidal effect is concerned, as fewer numbers
of bacteria appear to adhere on glass ceramic with higher fl orin content
(see Figure 7.12) [72].
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