Calcium Orthophosphate-Based Biocomposites and Hybrid Biomaterials - Calcium Orthophosphates: Applications in Nature, Biology and Medicine - page 589

Table 6.2 General respective properties from the bioorganic and

inorganic domains, to be combined in various composites
and hybrid materials [40].

Inorganic Bioorganic

Hardness, brittleness Elasticity, plasticity

High density Low density

Thermal stability Permeability

Hydrophilicity Hydrophobicity

High refractive index Selective complexation

Mixed valence slate (red-ox) Chemical reactivity

Strength Bioactivity

6.3 The Major Constituents of Biocomposites

and Hybrid Biomaterials for Bone Grafting

6.3.1 Calcium Orthophosphates

The main driving force behind the use of calcium orthophosphates
as bone substitute materials is their chemical similarity to the
mineral component of mammalian bones and teeth [25-27]. As a
result, in addition to being non-toxic, they are biocompatible, not
recognized as foreign materials in the body and, most importantly,
both exhibit bioactive behavior and integrate into living tissue by
the same processes active in remodeling healthy bone. This leads
to an intimate physicochemical bond between the implants and
bone, termed osteointegration [105]. More to the point, calcium
orthophosphates are also known to support osteoblast adhesion
and proliferation [106, 107]. Even so, the major limitations to use
calcium orthophosphates as load-bearing biomaterials are their
mechanical properties; namely, they are brittle with poor fatigue
resistance [29-31]. The poor mechanical behavior is even more
evident for highly porous ceramics and scaffolds because porosity
greater than 100 µm is considered as the requirement for proper
vascularization and bone cell colonization [108-110]. That is why, in
biomedical applications calcium orthophosphates are used primarily
as fillers and coatings [27].