MATERIALS FOR ORTHOPEDIC APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 90

3.8 OUTLOOK AND RECOMMENDATIONS FOR
FUTURE WORK
After reviewing the existing literature on synthesis, properties and different ap-
plications, it is quite clear that the appropriate material for each specifi c biomed-
ical application is still to be discovered.
In the case of ceramic-based monolithic and composite biomaterials, the
major concern is low fracture toughness in spite of having excellent biocompati-
bility. A vast research initiative is needed to increase the fracture toughness val-
ues of ceramic-based biomaterials up to the safe limit of use, by manipulating
microstructure and other structural parameters. An alternative route to develop-
ing biocompatible as well as mechanically-strong material is to develop ceramic
coatings on metal, which provide the biocompatibility of ceramics as well as the
mechanical strength of substrate metal. The properties of such ceramic coatings
depend on the coatings' thickness, deposition condition and the coating-substrate
interface properties. In both coating and bulk applications, the bioactive CaP
based ceramics are the most important implant materials due to their excellent
response inside human body. The fracture toughness of CaP based materials
should lie between 3 - 5 MPa m 0.5 .
The strategy to provide effective tools for bone replacement and repair
would be the use of Ca/P based biomaterials assisted osseointegration involving
an appropriate choice of the structure, microstructure, and chemical composi-
tions. This approach would, in principle, allow the production of bioactive
materials available “ off - the - shelf ” and with known predictable properties. At this
stage, microporosity has been suggested as one of the principal factors deter-
mining the osteoinductive properties of an implant 130 . However, mineral crystals,
morphologies, chemical composition and mechanical behaviour could also
play a major role in biological response and in the relative and/or combined
importance of these parameters in the manifestation of the osteoinductive
response. To this end, its duration and persistence have not yet been clearly
determined.
One of the key perspectives in orthopedic implants is the use of nanosized
Ca-phosphate particles. Both stoichiometric as well as non-stoichiometric HAp
powders would be used in producing nanobiocomposites of desired composition.
The interest for nanocrystalline apatite has grown since last few years. Apatite
nanocrystals are the main component of hard biological tissues such as bone and
dentine 131 and they play a major role in the biological activity of orthopedic bio-
materials 132,133,134 However, these reactive nanocrystals are diffi cult to shape into
available carriers without altering their nanocrystalline nature and their biologi-
cal properties are not yet totally understood to optimize their shape/function
properties.
Most of the polymers are currently used in soft tissue replacement such as
tendon, cartilage, skin, and so on. Except these, few polymers could be suitable in
load-bearing applications due to their lightweight, excellent corrosion resistance
in body fl uid and low COF. However, the major concerns for such applications