MATERIALS FOR ORTHOPEDIC APPLICATIONS - Advanced Biomaterials: Fundamentals, Processing, and Applications - page 55

TABLE 3.1. Mechanical Properties of Bioactive Glass/Ceramic/Ceramic Composites

Strength (MPa)

Elastic modulus,
E (GPa)

Fracture toughness,
KIC (MPa m 1/2 )

Materials Compressive Bending

Bioglasss (45S5) — 42 35 —

HAp 500 - 1000 115 - 200 80 - 110 < 1

20 vol% Y - TZP -
HAp composite

700 - 800 180 160 1.5

20 vol% Al 2 O 3 -
HAp composite

600 - 700 200 175 1.25

Glass - ceramic A - W 1080 220 118 2

[7,23,136] .

biocompatible and bioactive material, it has poor mechanical properties (see
Table 3.1), which limit its load bearing applications as bulk monolithic material.
To this end, hydroxyapatite could be used in combination with another metal/
ceramic phase, which can improve the mechanical properties of HAp without
deteriorating its biocompatibility. The motivation for developing HAp-based
composites stems from the requirement to fabricate materials with improved
strength and toughness properties with the least amount of reaction phases.
A popular application of HAp or in general, calcium phosphate (CaP) based
bioceramics, includes coatings on orthopedic and dental implants of metals and
their alloys 3,4 . All the above aspects are discussed in this chapter with the use
of experimental results on HAp-Ti or HAp-mullite composites. Also discussed
are the properties or performance of HAp coatings on metallic substrates (e.g.,
Co - Cr - Mo).
Among metals, titanium and its alloys have been extensively used as an im-
plant material in different medical applications for more than 30 years. This has
been facilitated by their excellent mechanical properties and high corrosion resis-
tance 5 . One of the primary advantages, originally cited for the titanium implant,
was its osseous integration 6 with the bone of the jaw. In recent years, however, this
attachment has been more accurately described as a tight apposition or mechani-
cal fi t and not true bonding 7 . Besides discussion on Ti alloys, particularly their
corrosion/wear properties, this chapter briefl y discusses the potential of some
metals, like Mg in biomedical applications.
Among various biopolymers (High Density Polyethylene (HDPE), Poly
Tetrafl uro Ethylene (PTFE), Polymethylmethacrylate (PMMA) etc.), are widely
used in biomedical applications, because of its excellent biocompatible property
along with better mouldability, availability as well as for its low cost 8 . In the last
few decades, substantial research efforts were invested to develop bioactive com-
posites as bone analogue replacement by reinforcing bioinert high density poly-
ethylene matrix with bioactive HAp ceramic particulates. As mentioned earlier,
the physical tribological and biocompatibility properties of HDPE-based bio-
composites will be discussed to a larger extent. While this chapter has attempted
to cover various materials from the perspective of biomedical applications, the