Biomedical Engineering Reference
In-Depth Information
surfaces generally demonstrated an increase in bone apposition compared to
polished or fi ne structured surfaces; the acid treated CpTi implants had an addi-
tional stimulating infl uence on bone apposition; the HA-coated implants showed
the highest extent of bone-implant interface, and; the HA coating consistently
revealed signs of resorption.
Generally, roughened surfaces have been used as the endosseous area of
a dental implant in order to increase the total area available for osseo-apposition.
However, there is still considerable controversy concerning the optimal surface
geometry and physicochemical properties for the ideal endosseous portion of
a dental implant. Knabe et al. [Knabe et al., 2002] used rat bone marrow cells
(RBM) to evaluate different Ti and HA dental implant surfaces. The implant
surfaces were a Ti surface having a porous Ti plasma-sprayed coating (Ti-TPS),
a Ti surface with a deep profi le structure (Ti-DPS), an uncoated Ti substrate
with a machined surface (Ti-ma), and a machined Ti substrate with a porous HA
plasma-sprayed coating (Ti-HA). RSM cells were cultured on the disc-shaped
test substrates for 14 days. The culture medium was changed daily and examined
for Ca and P concentration. It was reported that: all tested substrates facilitated
rat bone marrow cell growth of extra cellular matrix formation; Ti-DPS
and Ti - TPS to the highest degree, followed by Ti - ma and Ti - HA; Ti - DPS and
Ti-TPS displayed the highest cell density, and thus seems to be well suited for
the endosseous portion of dental implants, and; the rat bone marrow cells
cultured on Ti-HA showed a delayed growth pattern due to high phosphate
ion release.
The modern range of medical devices presents contrasting requirements for
adhesion in biological environments. For artifi cial blood vessels, the minimum
adhesion of blood is mandatory, whereas the maximum blood cell adhesion is
required at placed implant surfaces. Strong bio-adhesion is desired in many cir-
cumstances to assure device retention and immobility. Minimal adhesion is abso-
lutely essential in others, where thrombosis or bacteria adhesion would destroy
the utility of the implants. In every case, primary attention must be given to the
qualities of the fi rst interfacial conditioning fi lms of bio-macromolecules depos-
ited from the living systems. For instance, fi brinogen deposits from blood may
assume different confi gurations on surfaces of different initial energies, and thus
trigger different physiological events [Baier, 1986; Glantz et al., 1986].
Sunny et al. [Sunny et al., 1991] showed that the Ti oxide fi lm on Ti signifi -
cantly affects the adsorption rate of albumin/fi brinogen. Multinucleated giant
cells have been observed at interfaces between bone marrow and Ti implants in
mouse femurs, suggesting that macrophage-derived factors might perturb local
lymphopoesis, possibly even predisposing to neoplasia in the B lymphocyte
lineage. It has been found that an implant-marrow interface with associated giant
cells persists for at least 15 years, and that precursor B cells show early increase
in number and proliferative activity; however, at later intervals they do not differ
signifi cantly from controls. Rahal mentioned, in mice study, that following initial
marrow regeneration and fl uctuating precursor B cell activity, and despite the
presence of giant cells, Ti implants apparently become well-tolerated by directly
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