Biomedical Engineering Reference
In-Depth Information
Figure 3.7.
SEM images, revealing the adherence of L929 mouse fi broblast cells seeded for
24 hours on HAp-20Ti (a) & (b)
39
.
3.4.4 Glass-Ceramics Based Biomaterials
Glass ceramics are the polycrystalline materials, which are formed during pro-
longed heat treatment of glass at elevated temperature (above glass transition
temperature (T
g
)). This is an alternative route for synthesizing polycrystalline
ceramics. The amount of crystalline ceramic phase may vary between 50-99 vol%.
The important advantage of this route is that an almost pore-free body can be
fabricated, which is otherwise diffi cult to produce by sintering route.
In the last decade, a number of glass-ceramic systems are being researched
for their biomedical, in particular, dental restoration applications. It can be
recalled here that human teeth act as a mechanical device during masticatory
processes such as cutting, tearing, and grinding of food particles. Teeth get dam-
aged or worn away with age and therefore, partial or total replacement of human
teeth with a suitable biocompatible material is required.
3.4.4.1 Mica Based Glass Ceramics.
In recent times, the research on the
development of new dental restoratives has attracted wider attention, both in
the materials community as well as among dentists. It was also recognized that
bioceramic materials with enhanced mechanical, chemical, and tribological prop-
erties are believed to be a potential material for dental restoration purposes if
their machinability problem can be countered. In this context, machinable mica-
based glass ceramics appear to be a feasible solution to fabricate an all-ceramic
dental implant. The researchers in the authors' group
40
carried out a systematic
study to understand the infl uence of varying heat treatment conditions on SiO
2
-
MgO - Al
2
O
3
- K
2
O - B
2
O
3
- F (46SiO
2
, 16MgO, 17Al
2
O
3
, 10K
2
O, 7B
2
O
3
, 4F) glass-
ceramic system by adopting two sets of heat treatment experiments. In this
study, critical single stage heat treatment experiments were performed at 1000 °C
for varying soaking time of 8-24 hours with 4 hours time interval and as a
function of temperature for 4 hours in the temperature range of 1000-1120 °C
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