Biomedical Engineering Reference
In-Depth Information
and the surface topography are believed to be important in bone
contacting implants. They regulate the type and the degree of the
interactions that take place at the interface like adsorption of ions
and biomolecules such as proteins, formation of calcium phosphate
layers, and interaction with different types of cells (macrophages,
bone marrow cells and osteoblasts). Thus, the nature of the initial
interface that is developed between an artiicial material and
the attached tissue determines the ultimate success or failure of
the materials. Tissue compatibility is the most important issue to be
considered for the implant success.
Titanium is found to be well tolerated and nearly an inert material
in the human body environment. In an optimal situation, titanium
is capable of osseointegration with bone [43]. In addition, titanium
forms a very stable passive layer of TiO
2
on its surface and provides
superior biocompatibility. Even if the passive layer is damaged, the
layer is immediately rebuilt. In the case of titanium, the nature of
the oxide ilm that protects the metal substrate from corrosion is of
particular importance, and its physicochemical properties such as
crystallinity, impurity segregation etc, have been found to be quite
relevant.
Titanium alloys show superior biocompatibility when compared
to the stainless steel and Cr-Co alloys. The grain size of metal
implant inluences the osteoblast adhesion.
In vitro
studies carried
out using ultra ine-grained Cp Ti (grade 2) and Ti64 alloy exhibited
increased cell adhesion when compared to conventional materials.
This increase in cell adhesion is attributed to the increase in surface
energy at the grain boundaries.
Current trends in clinical dental implant therapy include
use of endosseous dental implant surfaces embellished with
nanoscale topographies. It has been shown, that implant surface
character is one implant design factor affecting the rate and extent
of osseointegration [21, 26, 89, 92]. According to Mendonça and
coworkers, nanostructured surfaces possess unique properties that
alter cell adhesion by direct (cell-surface interactions) and indirect
(affecting protein-surface interactions) mechanisms [89]. Surface
nanotopography appears to affect cell interactions at surfaces and
alter cell behavior when compared to conventional sized topography
[14, 16, 70, 89]. Nanotopography speciic effects on cellular behavior
have been demonstrated using a wide range of different cell types
including epithelial cells, ibroblasts, myocytes, and osteoblasts.
