Biomaterials - Bionanomaterials for Dental Applications - page 48

Current goals in the development of new Ti-based biomaterials
are: (i) to avoid potentially toxic elements, such as vanadium, to
further improve biocompatibility; (ii) to produce titanium alloys
with a high fatigue strength but a low Young's modulus compared
to cortical bone ( E = 10 − 25 GPa), to minimize stress shielding and
improve fracture healing. β -titanium alloys partially fulill these
requirements. They were developed already in the 1980s and 1990s,
but it usually takes years before new implant materials ind their
way into clinical application. One of these improved β titanium
alloys is Ti 12 Mo 6 Zr 2 Fe, which is currently used for implant materials.
Whether these new implant materials will prove to have superior
clinical properties compared to cp titanium and α + β titanium
alloys, has to be proven in clinical trials.
Implant sensitivity to titanium alloys is very seldom, despite
components such as vanadium which are described to be cytotoxic
[145]. In vivo studies have shown that Ti-6Al-4V has similar
biological compatibility to vanadium-free titanium alloys [40].
Titanium and its alloy are also getting much attention in dental
applications. Currently, Ti-based alloy is expected as an alternative
candidate to Ag-Pd-Au-Cu alloy. The representative dental titanium
alloys reported and their mechanical properties are shown in
Table 3.21 [95, 97, 102].
Some alloys have very different chemical compositions
from those for implants. Pure titanium and Ti-6Al-4V are the
main materials in the dental ield as well as in the surgical ield.
Ti-6Al-7Nb, which has been developed for surgical implants, is
also attractive for dental applications [68]. The casting process is
dominant in dental applications and especially the elongation which
is very low although the strength is kept to be high. Therefore, the
development in elongation without reducing strength is investigated
in cast titanium alloys.
Recently, Ti-40Zr, Ti-5Al-13Ta, and Ti-43.1 at.% Zr-10.2 at.%
Al-3.6 at.% V [37, 67] have been proposed. Titanium alloys are
very reactive and have relatively higher melting point comparing
with other dental alloys like Au based alloys and Ag based alloys.
Therefore, the low melting point titanium alloys and low reactive
mold materials are desired for dental precision castings. In dental
precision casting, alumina based, and magnesia based mold materials
are mainly used [146]. Magnesia based mold material is more