MATERIALS
The Role of Ceramic and
Glass Powder Processing in
Medical Devices
Employing factorial experimental design modelling during product development can bring a number of
benefits. These include consistency and improved quality of granulate coatings for metal implants as well as
the ability to predict possible osteoblast–osteoclast behaviour following implantation.
P. Jackson, CERAM, Penkhull, Stoke-on-Trent, UK
Taking control
Ceramic, glass and glass-ceramic powders are employed in a variety of medical
device applications. For example, they are
used directly as bone granulate for coating
metal implants, or as shaped bone
replacements, bone cements and dental
crowns. They also have a number of
important peripheral roles such as a core
or shell material in investment casting
of alloy implants. In the area of sensing,
ceramics have an important role to play;
for example, the piezoelectric components essential in ultrasound scanning are
ceramic.
Understanding and then controlling the
variables at play during the production of
primary ceramic or glass powders (and the
subsequent use of these powders to shape
or coat components) is critical to medical
device manufacturers. Failure to do so will
mean batch-to-batch variations in chemistry and granulate size/strength; this in
turn will deliver variable bioactivity and
component durability. This article explains
how the utilisation of testing and modelling
informs research and development (R&D)
and enables product development.
The control of variables starts with the
production of primary powders. These are
typically produced in two ways.
■ Precipitation, which involves combining solutions (often at a controlled pH)
to generate a solid powder product that is
suspended in the remaining liquid phase.
The solid product is then recovered by
filtration or centrifuge. It is then washed,
dried and perhaps further processed, for
example, by sintering.
■ Calcination of two or more precursor
powders.
With both methods of production, there
are a large number of variables with poten-
tial to affect subsequent processing and the
final product quality. For calcination, for
example, variables include:
■ purity, crystallinity, particle size
distribution of precursor powders
■ method of mixing (dry or as a wet
suspension)
■ density of packing in the refractory box
(sagger) containing the powders that are
inside the kiln
