of their tensile strength, the elastic modulus (Fig. 4), and biostability. The most
important synthetic nondegradable polymers in bone tissue engineering are
polyethylene (PE), polypropylene (PP), selected polyurethanes (PUs), polytetrafluoroethylene (PTFE), poly(vinyl chloride) (PVC), polyamides (PAs), poly
(methyl methacrylate) (PMMA), polyoxymethylene (POM, polyacetal resin),
polycarbonate (PC), poly(ethylene terephtalate) (PET), poly(ether ether ketone)
(PEEK), and polysulfone (PSU). These polymers have several applications in the
medical field, ranging from PTFE vascular grafts to ultrahigh molecular weight
polyethylene (UHMWPE) acetabular cups [8, 85, 86].
6 Polymer/HAp Composites in Bone Tissue Engineering
Nanocomposites with bone-like properties depend on two main factors: (a) interfacial adhesion should be good between organic polymers and inorganic HAp, and (b)
the dispersion of HAp should be uniform at the nanolevel in the polymer matrix
[87]. Poor interface between phases is due to the lack of adhesion between HAp
particles and the polymer matrix. Additionally, HAp might agglomerate if it is not
evenly dispersed in the polymer matrix through proper processing methods, which
causes poor mechanical properties. During the past few decades, significant efforts
have been made to synthesize polymer/nanoHAp systems that resemble bone
structure. Generally, both nondegradable and degradable polymers are used for
fabrication of polymer/HAp composite materials in bone tissue engineering.
6.1 Nondegradable Polymer/HAp Nanocomposites
Nondegradable polymers have good mechanical properties and chemical stability.
Therefore, they are widely used in bone tissue engineering. However, improvement
of their biocompatibility and performance are highly desirable in terms of clinical
applications. The nondegradable polymer/HAp systems are generally applied for
tissue that cannot be regenerated due to its large losses and, in the case of elderly
patients, with a less effective tissue self-healing ability. The use of PMMA as
nondegradable polymer is described below.
6.1.1 Poly(methyl methacrylate)
PMMA and its derivatives have been used most often in the bone cements used for
fixation in orthopedic surgeries. PMMA is an amorphous thermoplastic polymer. It
gives excellent optical clarity, weather resistance, surface hardness, good chemical
resistance, rigidity, dimensional stability, low mold shrinkage, good impact
strength, nontoxicity, and tastelessness. PMMA powders can be injected and
Hydroxyapatite-Packed Chitosan-PMMA Nanocomposite: A Promising Material for. . .
153
important synthetic nondegradable polymers in bone tissue engineering are
polyethylene (PE), polypropylene (PP), selected polyurethanes (PUs), polytetrafluoroethylene (PTFE), poly(vinyl chloride) (PVC), polyamides (PAs), poly
(methyl methacrylate) (PMMA), polyoxymethylene (POM, polyacetal resin),
polycarbonate (PC), poly(ethylene terephtalate) (PET), poly(ether ether ketone)
(PEEK), and polysulfone (PSU). These polymers have several applications in the
medical field, ranging from PTFE vascular grafts to ultrahigh molecular weight
polyethylene (UHMWPE) acetabular cups [8, 85, 86].
6 Polymer/HAp Composites in Bone Tissue Engineering
Nanocomposites with bone-like properties depend on two main factors: (a) interfacial adhesion should be good between organic polymers and inorganic HAp, and (b)
the dispersion of HAp should be uniform at the nanolevel in the polymer matrix
[87]. Poor interface between phases is due to the lack of adhesion between HAp
particles and the polymer matrix. Additionally, HAp might agglomerate if it is not
evenly dispersed in the polymer matrix through proper processing methods, which
causes poor mechanical properties. During the past few decades, significant efforts
have been made to synthesize polymer/nanoHAp systems that resemble bone
structure. Generally, both nondegradable and degradable polymers are used for
fabrication of polymer/HAp composite materials in bone tissue engineering.
6.1 Nondegradable Polymer/HAp Nanocomposites
Nondegradable polymers have good mechanical properties and chemical stability.
Therefore, they are widely used in bone tissue engineering. However, improvement
of their biocompatibility and performance are highly desirable in terms of clinical
applications. The nondegradable polymer/HAp systems are generally applied for
tissue that cannot be regenerated due to its large losses and, in the case of elderly
patients, with a less effective tissue self-healing ability. The use of PMMA as
nondegradable polymer is described below.
6.1.1 Poly(methyl methacrylate)
PMMA and its derivatives have been used most often in the bone cements used for
fixation in orthopedic surgeries. PMMA is an amorphous thermoplastic polymer. It
gives excellent optical clarity, weather resistance, surface hardness, good chemical
resistance, rigidity, dimensional stability, low mold shrinkage, good impact
strength, nontoxicity, and tastelessness. PMMA powders can be injected and
Hydroxyapatite-Packed Chitosan-PMMA Nanocomposite: A Promising Material for. . .
153