34 | www.CosmeticsandToiletries.com Vol. 130, No. 7 | September 2015
RESEARCH | C&T
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© 2015 Allured Business Media.
At a first glance, teeth impact appearance. Healthy teeth support self-confidence, well-being and beauty and in most cultural groups, white, shiny and healthy-looking teeth make a positive impression.
The visible crowns of teeth are covered by an up to 3-mm thick enamel layer
comprising approximately 96% of the mineral hydroxyapatite. Although
hydroxyapatite is the hardest substance in the human body, teeth are
exposed to continuous aging by physicochemically driven, constant wear of
Enamel is built up early during ontogenesis and it cannot regrow.
Removed enamel is substantially lost and this loss may become a problem
over the years; aged teeth begin to look dull and sensitivity can develop. The
two primary triggers responsible for dental wear are: an acidic environment
and mechanical forces.
Hydroxyapatite: Due to its chemical structure, hydroxyapatite is
sensitive to acids, which destroy it by releasing calcium ions and hydrogen
phosphates. Hydroxyapatite demineralizes at pH values below 5. 5. 1 Such
demineralization occurs either by exposure to bacterial metabolites, leading
to cavity formation, or by consuming acidic nutrients, which induces
enamel erosion. 2 Further, while hydroxyapatite is harder than other minerals, rating a moderate 5 on the Mohs scale, 3 substances of equal or greater
hardness can mechanically remove enamel by abrasion.
Repair technologies: To meet consumers’ needs for products repairing
damaged or refilling worn enamel, several technologies were marketed in
toothpastes. Fluoride is the most important one and its main benefit is remineralization. Following the demineralization of hydroxyapatite, due to a
low pH, fluoride interacts with the remaining apatite and forms fluoridated
hydroxyapatite. Fluoridated hydroxyapatite improves enamel hardness and
resistance to acidic attacks, in turn reducing the risk of cavity formation. 4, 5
To repair small fissures or refill worn enamel, zinc hydroxyapatite is
another technology introduced, which due to its biomimetic structure,
is reported to bind to the surface of enamel and close small microscopic
defects. 6 The toothpaste containing it does not contain fluoride, most likely
because the hydroxyapatite would react with the fluoride ion and form
fluorapatite within the formula.
The combination of both approaches in one formula—i.e., repairing demineralized and refilling worn enamel—would be a significant
improvement for oral care. As such, presented here is a fluoride-compatible
Thomas Welss, Claudia Hundeiker,
Nicole Duschek, Wilfried Howorka,
Jennifer Evening and Thomas Förster
Henkel Beauty Care, Düsseldorf, Germany
Shielding and Repairing Tooth Enamel with
enamel • hydroxyapatite •
carboxymethyl cellulose •
repair • refill • microscopy •
nano-indentation • surface
This article evaluates the
ability of a toothpaste
and a film-building
carboxymethyl cellulose to
repair and refill damaged
and elasticity were
quantified by nano-indentation, and surface
roughness by profilometry.
microscopy was employed
for qualitative analysis, and
profilometry, again, for the
refilling of micro damage.