Biomedical Engineering Reference
In-Depth Information
Condition
Type of crystalline structure of formed titanium oxide
Physical depositon
Anatase
Dry oxidation
Rutile
Wet oxidation
Rutile
Low pH
(acid)
R + A
Anatase
Solution pH
High pH
(alkaline)
Figure 5.2. Types and stabilities of oxides formed on titanium materials.
and anatase type oxides are stable at normal conditions. Figure 5.2 summarizes
the formation of these oxides under various forming processes [Oshida, 2007a].
It is of interest to note that choice for rutile formation or anatase formation
depends on the acidity of used electrolyte.
Mechanically polished (with SiC paper grit #600) commercially pure
titanium (ASTM CpTi Grade 4) plates (10
×
3 0
×
2 mm) were variously
chemical - treated:
(1) AC: acid - treated (HF/HNO 3 /H 2 O) at room temperature for fi ve seconds,
(2) AK: alkaline - treated (5 mol NaOH) at 70 ° C for 24 hours, and
(3) HP: hydrogen peroxide - treated (50%) at room temperature for ten
seconds.
Such chemically-treated surfaces were examined for surface roughness and
surface contact angle measurements. Figure 5.3 shows their relationship, where
mark “ 4 ” represents AC - treated surface, while marks “ 5 ” and “ 7 ” represent AK -
treated and HP - treated surfaces, respectively.
It was observed that AC-treated surface shows the hydrophobic nature, while
AK- and HP-treated surfaces show hydrophilic character. After chemical strip-
ping surface oxide fi lms from titanium substrate, the thus isolated oxide fi lms
were subjected to TEM (transmission electron microscopy) to identify the crys-
talline structure(s). It was also found that AC-treated hydrophobic surface oxide
was made of only rutile type TiO 2 , while AK - and HP - treated surfaces consisted
of a mixture of rutile and anatase type oxides [Lim et al., 2001; Oshida, 2007b].
The level of neutrophil priming and activation following implant placement
may be linked to the development and maintenance of long-term stability and
osseointegration [Gaydos et al., 2000]. Bisphosphonate effect on neutrophil acti-
vation was furthermore examined on these differently treated surfaces. Neutro-
phils were isolated from whole blood collected from healthy human donors, on
a double dextran gradient. Treated surfaces were incubated with 5
1 0 5 neutro-
phils per curette. Luminol-dependent CL (chemiluminescence) was recorded for
60 minutes (priming or infl ammatory phase), followed by secondary stimulation
with 10 − 7 M phorbol myristate acetate at 60 minutes (activation phase) for a
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