Biomedical Engineering Reference
In-Depth Information
surface structure, surface chemistry, and/or surface energy of a scaffold for
the selective promotion of the adhesion of one type of cell while inhibiting
other types of cells.
50
6.3.1.5 Zirconia
Zirconia implants that might offer a useful alternative to titanium have recently
been introduced into dental implantology.
40,50
Zirconia has an opacity that
resembles natural teeth while titanium implants can give an unnatural bluish/
gray appearance.
31
Unlike titanium, the bright white color of zirconia may pro-
vide satisfactory aesthetics.
50
The development of yttria-stabilized tetragonal PSZ has rekindled interest in
ceramic implant materials for dental implants.
50
Unlike aluminum oxide ceram-
ics used in dental implants, PSZ has a higher fracture resistance and flexural
strength making it less sensitive to stress concentrations. This is due to the meta-
stable tetragonal grain structure that is transformed into a monoclinic struc-
ture at room temperature.
161
Several studies showed the capability of zirconia
implants to withstand long-term loading.
185,186
The use of zirconia implants have shown fewer inflammatory infiltrates in soft
tissue than for titanium.
34
Unlike titanium, minimal ion release is detected
187
; hence,
zirconia is considered to be highly biocompatible. Zirconia implants have been
reported to integrate well in the jaw bone
28,29,38
and can be produced as one-piece
implants that heal nonsubmerged (i.e. transmucosal) following implantation.
50
Andreiotelli et al.
52
concluded that zirconia may have the potential as a suc-
cessful implant material but recommended that clinical application be supported
by clinical studies. Implant loading can influence osseointegration.
50
Based on
studies by Akagawa et al. who compared submerged and nonsubmerged zir-
conia implants, collagen fibers in the apical regions of submerged implants in
dogs were observed after 3 months.
28
This effect was explained as the result
of mastication of food. A loss of crestal bone was described after 3 months in
loaded implants.
188
In a study performed in monkeys, Kohal et al. compared
loaded sandblasted zirconia and sandblasted, acid-etched titanium implants in
the anterior bone.
38
After 9 months of healing and 5 months of loading, the soft
and hard tissue dimensions were evaluated. The results indicated that the BIC
reached 67% for zirconia implants and 73% for titanium implants without sta-
tistically significant difference.
6.3.2 Nanomaterials for Cartilage Applications
Cartilage replacement is one of the necessities in medical treatments. This is
because, once cartilage is damaged, it does not normally regenerate. Repeated
injury plus the low cellularity and isolation from the vascular supply of bioac-
tive molecules limit intrinsic cartilage repair. As a result, mature articular car-
tilage cannot heal spontaneously because of its low mitotic activity in contrast
with the rapid rate of chondrocytic (cartilage-synthesizing cell) mitosis during
