Restorative
materials in the new era aim to be “bio-active” and long-lasting. It has been
suggested that the anti-inflammatory activity of some non-steroidal
anti-inflammatory drugs (NSAIDs) may be partly due to their ability to scavenge
reactive oxygen species (ROS) and reactive nitrogen species (RNS), as well as
to inhibit the respiratory burst of neutrophils triggered by various activating
agents. As a part of our continuous interest of developing functional dual action
restorative materials capable of being “bio-active” and long-lasting, we design
and evaluate novel chitosan hydrogels containing krill oil (antioxidant containing
material), naproxen, ibuprofen (non steroidal anti-inflammatory medication),
aspirin (pain relieve medication and free radical scavengers) and combinations
thereof (chitosan-H-krill oil, chitosan-H-krill oil-aspirin and
chitosan-H-naproxen, chitosan-H-naproxen-krill oil, chitosan-H-krill
oil-ibuprofen and chitosan-H-ibuprofen) as functional additive prototypes for
further development of “dual function restorative materials”; secondly,
determine their effect on the dentin bond strength of a composite and thirdly,
evaluate the capability of newly designed hydrogels to play an integral role of
“build in” free radical defense mechanism by using BSA solubility as a
“molecular prototype” of the site of free radical attack in vitro. Materials and Methods: The above mentioned hydrogels
were prepared by dispersion of the corresponding component in glycerol and
acetic acid
with the
addition of chitosan gelling agent. The surface morphology (SEM), release
behaviors (physiological pH and also in acidic conditions), stability of the
therapeutic agent-antioxidant-chitosan and the effect of the hydrogels on the
shear bond strength of dentin were also evaluated. Results: The release of
aspirin, ibuprofen and naproxen confers the added benefit of synergistic action
of a functional therapeutic delivery when comparing the newly designed chitosan-based
hydrogel restorative materials to the commercially available products alone.
Neither the release of aspirin, ibuprofen or naproxen nor the antioxidant
stability was affected by storage over a 6- month period. The hydrogel
formulations have a uniform distribution of drug content, homogenous texture
and yellow color (SEM study). All chitosan dentin treated hydrogels gave
significantly (P < 0.05;
non-parametric ANOVA test) higher shear bond values (P < 0.05) than dentin treated or not treated with phosphoric
acid. The model protein (BSA) was adopted to evaluate the chitosan-based
functional biomaterials as defense for undesired free radical formation under in vitro conditions. Conclusion: The
added benefits of the chitosan treated hydrogels involved positive influence
on the aspirin, ibuprofen and naproxen release, increased dentin bond strength
as well as demonstrated in vitro “build in” free radical defense mechanism, therefore acting as a “proof of
concept” for the functional multi-dimentional restorative materials with the
build in free radical defense mechanism.