Biomedical Engineering Reference
In-Depth Information
the cell response (proliferation, differentiation) that would eventually lead to bone forma-
tion. For this reason, the microarchitecture of the surface (topography, roughness, etc.)
and its chemical composition are important determinants of the response of the biologic
system to the implant.
Immediately after implant placement, a series of events occur between the host and the
surface of the implants (Lemons, 2004). This sequence of events includes the initial interac-
tion between blood and the implant surface, where proteins and ligands are dynamically
adsorbed onto and released from the implant surface, through an inflammatory process,
which is followed by initial bone formation around the implant (modeling), and through
several remodeling cycles, where bone surrounding the implant achieves its highest degree
of organization and mechanical properties (Lemons, 2004). Because of the dynamic nature
of the bone-biomaterial interface as a function of implantation time, endosseous dental
implant biomaterials must have short- and long-term biocompatible and biofunctional
properties (Coelho et al., 2009).
From the point of view of physics, a surface may be defined as the sudden interrup-
tion of the atomic arrangement. This sudden interruption results in differences between
surface and bulk electronic properties, leading to different physico/chemical behavior
between the two regions of the material. Therefore, from a theoretical standpoint, differ-
ent modification methods utilized for implant surface engineering may lead to different
and unique surface properties (Kittel, 1995). These different physico/chemical properties
can potentially lead to changes in the host-to-implant response. New surface treatments
should be tested as new biomaterials. As examples, the alteration of surface topography or
the incorporation of bioactive ceramics as coatings have been investigated and utilized on
a large scale by implant dentistry practitioners with no or limited surface characterization
(Lemons, 2004; Coelho et al., 2009).
Despite the extensive literature accumulated over the past decades concerning the host/
biomaterial response, several considerations should be taken into account concerning the
complex effects of endosseous dental implants surface modifications during and after the
process of osseointegration. Biological considerations, such as biocompatibility and osseo-
conductivity of the implant, should be addressed. In addition, specific surface effects on
initial bone healing kinetics and mechanical properties evolution as implantation time
elapses in vivo, as well as the in vivo stability of the surface (often regarded as one of
the leading factors of long-term osseointegration) should be hierarchically investigated to
more fully evaluate implant therapy surgical and/or prosthetic protocol modifications.
A hierarchical approach, where in vitro testing followed by laboratory animal research
leads to subsequent controlled prospective and/or retrospective clinical trials, is often
neglected before new biomaterials are commercially introduced. Therefore, treatment pro-
tocol changes, such as a decrease in the time allowed for osseointegration of immediate/
early loaded dental implants, have often followed empirical rationales.
BasicResearchMethodsforImplantSurfaceEvaluation
Biocompatibility of Biomaterials
Before clinical trials, new biomaterials (including surface modifications) should undergo
in vitro and in vivo evaluation. This type of evaluation typically follows a hierarchical
