Biomedical Engineering Reference
In-Depth Information
coatings have been developed for the modification of the tooth surface in vivo. Easy-to-clean surface
properties are achieved by integrating nanometer-sized inorganic particles into a fluoro-polymer
matrix
[40]
. These biocompatible surface coatings have a surface free energy of 20
25 mJ/m
2
—
known as theta surfaces
[41]
—and therefore can facilitate the detachment of adsorbed salivary pro-
teins and adherent bacteria under the influence of physiological shearing forces in the mouth
(
Figure 2.1C
)
[40]
. Easy-to-clean coatings are conceivable for patients with high caries risk, such as
those suffering from mouth dryness owing to dysfunctional salivary glands—termed xerostomia—or
for individuals who do not practice proper oral hygiene. Possible applications could be tooth sealants
as well as coatings of restorations, dentures, or transmucosal parts of implants. Even tooth fissures
sealed with this material could be cleaned more easily by the shear forces from tooth brushing.
Other nano-enabled approaches for biofilm management are oral health-care products that contain
bioinspired apatite nanoparticles, either alone or in combination with proteinaceous additives such as
casein phosphopeptides (CPP)
[42,43]
. CPP-stabilized amorphous calcium phosphate (ACP) nano-
complexes with a diameter of 2.12 nm
[44,45]
seem to play a pronounced role in biomimetic strate-
gies for biofilm management. There is in vivo evidence indicating that CPP
ACP complexes reduce
bacterial adherence by binding to the surfaces of bacterial cells, the components of the intercellular
plaque matrix, and to adsorbed macromolecules on the tooth surface (
Figure 2.1D
)
[46,47]
.
CPP
ACP-treated germanium surfaces that are applied in the oral cavity for up to 1 week have been
shown to significantly delay the formation of biofilms. However, it should be emphasized that
because germanium is not a biomineral, the clinical relevance of the study remains limited. Other
in vivo experiments have shown that nonaggregated and clustered hydroxyapatite (HAP) nanocrys-
tallite particles (average size 100
5nm
3
) can adsorb onto the bacterial surface and interact
with bacterial adhesions to interfere with the binding of microorganisms to the tooth surface
[42]
.
These bioinspired strategies for biofilm management are based on size-specific effects of the
apatite nanoparticles and are thought to be more effective than traditional approaches that use
micrometer-sized HAP in toothpastes. HAP has been adopted for years in preventive dentistry; how-
ever, effective interaction of the biomineral with the bacteria is only possible if nanosized particles
that are used are smaller than the microorganisms (
Figure 2.1D
). Finally, oral health-care products
based on bioinspired nanobiomaterials have moved from the laboratory to daily application—as a
supplement to conventional approaches—for biofilm control and remineralization of submicrometer-
sized enamel lesions. Easy-to-clean, wear-resistant, and biocompatible nanocomposite surface
coatings for biofilm management are close to being used in dental practice. However, biomimetic
restoration and filling of small clinically visible cavities with nanobiomaterials is not conceivable at
the moment and requires further extensive research with respect to clinical applicability. It should
also be kept in mind that biomimetic enamel surfaces are still susceptible to caries if patients neglect
conventional oral health care such as tooth brushing or fluoride application
[48]
.
10
3
3
2.6
Nanobiomaterials in restorative dentistry
2.6.1
Dental nanocomposites
The demand by patients for tooth-colored restorations, concerns regarding environmental impact,
and the adverse clinical reactions to amalgam-filling materials have accelerated research into the
development of alternative restoratives. However, despite the development of
resin-based
