Biomedical Engineering Reference
In-Depth Information
TABLE 4.1
Properties of Bone, Teeth, and Biomaterials
Young's Modulus
E
(GPa)
Density ρ
(g/cm
3
)
Strength
(MPa)
References
Material
Hard Tissue
Tooth, bone, human
compact bone, longitudinal
direction
17
1.8
130 (tension)
Craig and Peyton (1958);
Reilly and Burstein
(1975); Peters et al. (1983);
Park and Lakes (1992)
Tooth dentin
18
2.1
138 (compression)
Tooth enamel
50
2.9
Polymers
Park and Lakes (1992)
Polyethylene (UHMW)
1
0.94
30 (tension)
PMMA
3
1.1
65 (tension)
PMMA bone cement
2
1.18
30 (tension)
Metals
Park and Lakes (1992)
316L Stainless steel
(wrought)
200
7.9
1000 (tension)
CoCrMo (cast)
230
8.3
660 (tension)
CoNiCrMo (wrought)
230
9.2
1800 (tension)
Ti6A14V
110
4.5
900 (tension)
Composites
Graphite-epoxy
(unidirectional fibrous,
high modulus)
215
1.63
1240 (tension)
Schwartz (1992)
Graphite-epoxy (quasi-
isotropic fibrous)
46
1.55
579 (tension)
Schwartz (1992)
Dental composite resins
(particulate)
10-16
170-260
(compression)
Cannon (1988)
Foams
Gibson and Ashby (1988)
Polymer foams
10
−4
−1
0.002-0.8
0.01-1 (tension)
to contribute to leakage of saliva, bacteria, and so on, at the interface margins. Such leakage in some
cases can cause further decay of the tooth.
Use of colloidal silica in the so-called “microfilled” composites allows for these resins to be polished,
so that less wear occurs and less plaque accumulates. It is more difficult, however, to make these with
a high fraction of filler. All the dental composites exhibit creep. The stiffness changes by a factor of
2.5-4 (depending on the particular material) over a time period from 10 s to 3 h under steady load
(Papadogianis et al., 1985). This creep may result in indentation of the restoration, but wear seems to be
a greater problem.
Dental composite resins have become established as restorative materials for both anterior and pos-
terior teeth. The use of these materials is likely to increase as improved compositions are developed and
in response to concern over long-term toxicity of silver−mercury amalgam fillings.
4.5 Fibrous Composites
Fibers incorporated in a polymer matrix increase the stiffness, strength, fatigue life, and other proper-
ties (Agarwal and Broutman, 1980; Schwartz, 1992). Fibers are mechanically more effective in achieving
a stiff, strong composite than are particles. Materials can be prepared in fiber form with very few defects
which concentrate stress. Fibers such as graphite are stiff (with a Young modulus of 200-800 GPa) and
