Biomedical Engineering Reference
In-Depth Information
Table 1.1
Mechanical properties of conventionally processed and nanostruc-
tured CP Grade 4 titanium.
State
Processing/treat-
ment conditions
UTS,
MPa
YS,
MPa
Elongation,
%
Reduction
area, %
Fatigue
strength at
10
6
cycles
1
Conventional Ti
As received
700
530
25
52
340
2
n i
ECAP+TMT
1240
1200
12
42
620
3
Annealed
Ti-6Al-4V ELI
940
840
16
45
530
reductions (to below 10% elongation to failure) normally seen at er roll-
ing or drawing.
Laboratory fatigue studies of nanostructured and conventional CP tita-
nium conducted in air at room temperature were performed per ASTM E
466-96 at a load ratio R (rmin/rmax) = 0.1 and loading frequency of 20 Hz.
Table 1.1 also shows that the fatigue strength of nanostructured CP tita-
nium at er one million cycles is nearly two times higher than conventional
CP titanium and exceeds that of the Ti-6Al-4V alloy [175, 176].
Cytocompatibility tests utilizing mouse i broblast cells L929 were
undertaken to verify the previously reported benei ts of nanostructured
CP titanium vis à vis conventional coarse-grained CP Ti. h is study was
performed, as described elsewhere [183], with hydrol uoric acid surface
etching being performed prior to cell exposure. Figure 1.2 shows the etched
conventional and nanostructured titanium surfaces, respectively. h e dif-
ferences in surface roughness of these materials are easily seen, a homoge-
neous and nanometer-sized roughness being apparent for nanostructured
titanium compared with the much coarser structure for etched CP Grade
4 titanium.
h e cell attachment investigation shows that i broblast colonization of the
CP Grade 4 titanium surface dramatically increases at er nanostructuring,
as shown in Figure 1.3. For example, the surface cell occupation for conven-
tional CP Ti was 53.0% at er 72 hrs in contrast to 87.2% for nanostructured
CP Grade 4 (Table. 1.2). h e latter observations also coni rm the previ-
ous studies [181, 184, 185], showing that cell-adhesion on nanostructured
titanium is greater than on conventional CP Grade 4 titanium. h is result
suggests that a high osseointegration rate should be expected with nano-
structured CP Grade 4 titanium when compared to conventional titanium.
