Biomedical Engineering Reference
In-Depth Information
on the nanoscale.
106
With these advanced techniques, enamel erosion has
been found to occur in three stages: enamel softening, enamel material
loss on a microscopic scale, and macroscopic enamel loss. Based on
the above findings from nanoindentation, healthy functional soft drinks
contain calcium and phosphate were developed and introduced to
market.
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4.3.
Assessment of dental treatments
Bleaching of teeth is gaining popularity for cosmetic reasons. Present
tooth-bleaching techniques use hydrogen peroxide as the active agent. It
is applied directly, or produced in a chemical reaction from sodium
perborate-carbamide peroxide. Hydrogen peroxide is a reactive oxygen
species, along with superoxide (O
2
·
), hydroxyl radical (HO˙), peroxyl
(ROO) and alkoxyl (RO).
107
These free radicals oxidize a wide variety of
organic and inorganic compounds by attacking the long chained, dark
colored chromophore molecules and split them into smaller, less
intensely colored and more diffusible molecules. Although the bleaching
treatments have been exposed to numerous evaluations,
108
the effect
these have on teeth is still largely unknown, especially the potential
harmful effects of free radicals on organic components of enamel.
Recently, nanoindentation was used to evaluate the effects of bleaching
agents on the mechanical properties of human teeth.
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The results
illustrated that the mechanical properties of the bleached dentin were
significantly decreased. For intertubular dentin, the mean hardness
decreased by 29-55% and the mean elastic modulus decreased by 19-
43%. For enamel, the mean hardness decreased by 13-32% while the
mean elastic modulus decreased by 18-32%.
As a common daily oral hygiene procedure, tooth brushing may have
abrasive effects on the surface of enamel, especially acid-softened
enamel. AFM nanoindentation was employed to investigate the issue
110
and the results indicated that tooth brushing of surface softened enamel
leads to minor changes in the surface morphology and nanomechanical
properties; the amount of enamel lost due to tooth brushing was
independent of the demineralization time and was lower compared to the
mineral loss caused by the demineralization treatments. The exposure to
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