A Materials Database for Medical Devices

4
MATERIALS
Vitamin E added to UHMWPE provides oxidation stability
Two new grades of ultrahigh molecular weight polyethylene
(UHMWPE) containing vitamin E (alpha-tocopherol)
have been announed by Ticona, Germany. The addition of a
biocompatible antioxidant provides these new grades with
effective oxidation stability. The aim is to further extend the
lifetime of orthopedic implants.
Stabilization with vitamin E is intended to reduce suscepti-
Dynamet, a subsidiary of Carpenter
Technology, Washington, Pa., has
developed a new line of smalldiameter
titanium machining bar that
provides very tight dimensional
tolerances and exceptional size
consistency and straightness. Called
UltraBar, it offers improved quality
and higher productivity for small,
intricate, precision parts made on
Swiss-type automatic screw
machines. It is suitable for posts,
abutments, and healing caps in
dental implants. Thedra Wagner,
Dynamet, 195 Museum Road,
Washington, PA 15301; tel: 800/237-
9655; fax: 724/229-4195;
twagner@cartech.com;
www.dynamet.com.
Nanofibrous scaffolds for bone
grafting of large gaps in bone have
reportedly been developed by Prof.
Xiaojun Yu, Stevens Institute of
Technology, Hoboken, N.J. He has
proposed a way to incorporate
nanofibers onto biodegradable
polymeric three-dimensional
scaffolds that have optimal porosity
due to open geometrics and large
surface area. This porosity permits
the necessary nutrient transport and
cell penetration into the scaffold for
successful repair of large bone
defects. Xiaojun Yu, Stevens Institute
of Technology, Hoboken, NJ 07030-
5991; tel: 201/216-5256;
xyu@stevens.edu; www.stevens.edu.
Wright Medical Group Inc. has
released Pro-Dense Injectable
Regenerative Graft, a bone graft
substitute that is a composite of
calcium phosphate and sulfate. It
features a unique, tri-phasic
resorption profile providing the
biologic environment to allow the
body to quickly and reliably
regenerate dense new bone.
Extensive animal testing found that
new bone was of greater density and
greater compressive strength at 13
weeks than the new bone
regenerated by autograft, and
formed new bone at a faster rate than
autograft. John K. Bakewell, Wright
Medical Group Inc., Arlington, TN;
tel: 901/867-4527; www.wmt.com.
bility to oxidation during sterilization.
GUR polymers meet the requirements of standard ASTM F648 published
by the American Society for Testing and Materials and ISO standard
5834-1/-2 for starting materials and semi-finished products.
For more information: Henning Kull, Ticona, Kelsterbach, Germany; tel: 49
(0) 6107 772 17 97; fax: 49 (0) 6107 772 72 31; kuell@ticona.de; www.ticona.com.
Ticona North American Headquarters, 8040 Dixie Highway, Florence, KY 41042;
tel: 800/833-4882.
Layers yield stronger, more successful bone implants
A new method for layering two kinds of
biomaterials into one strong, yet porous
unit that may lead to improved reconstruction
or repair of bones is under development
by researchers from the American
Dental Association Foundation (ADAF)
and the National Institute of Standards and
Technology (NIST).
First, a macroporous calcium phosphate
cement (CPC) paste is placed into the area
needing reconstruction or repair. Then, a
fiber-reinforced CPC paste is layered onto
the first to support the new implant. After
new bone has grown into the macroporous
layer and increased its strength, the ab-
High-magnification scanning electron
microscopy shows (center of micrograph)
the leg of an osteoblast (bone precursor),
called a cytoplasmic extension, attaching
to nano-sized hydroxyapatite crystals,
similar to those in natural bone.
sorbable fibers in the strong layer dissolve and create additional macroporous
channels that promote even more bone ingrowth. This method mimics the natural
bone structure in which a strong layer of cortical bone covers and
strengthens a weaker macroporous layer of spongy bone.
For more information: Elena Burguera, National Institute of Standards and
Technology, 100 Bureau Drive, Gaithersburg, MD 20899-8546; tel: 301/975-
5296; Elena.burguera@nist.gov; www.nist.gov. Contact: Michael E. Newman,
tel: 301/975-3025; michael.newman@nist.gov.
Image contrast grade of polymer provides tailored opacity
Invibio has introduced an image contrast grade of Peek-Optima polymer.
The new image contrast grade offers the superior mechanical, physical, and
biocompatible properties of unfilled polymer with the added advantage of tailored
opacity, enabling medical device manufacturers to develop implants that
can be observed more clearly with X-ray and CT imaging while remaining
compatible with MRI.
Unlike metals, the image-contrast grade provides medical device manufacturers
the flexibility to tailor the radiographic, CT, and MRI visibility of an implant
to suit a particular application. Now it is possible for device manufacturers
to achieve an appropriate balance of implant and tissue visualization
without image artifacts or scatter.
For more information: Invibio Inc., 300 Conshohocken State Road, West Conshohocken,
PA 19428; tel: 866/468-4246 or 484/342 6004; www.invibio.com.
66 ADVANCED MATERIALS & PROCESSES/JANUARY 2008