Health and Tips:Home Teeth Whiteners May Weaken Enamel

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HEALTH TIP: Home teeth whiteners may weaken enamel

Teeth bleaching products for home use may minimally reduce the surface hardness of tooth enamel and enamel’s ability to “bounce back” from normal wear and tear, a laboratory study suggests.

Still, “the public should not be alarmed of the bleaching process,” said Dr. Shereen S. Azer, at The Ohio State University College of Dentistry in Columbus.

“In reality — or clinically speaking — these effects may not be detectable,” Azer told Reuters Health.

Moreover, Azer said, “human enamel has been shown to heal itself and ‘remineralize’ over time, meaning it has the ability to restore back the levels of surface calcium that has been lost due to bleaching.” This is particularly evident with subsequent fluoride treatments and use of fluoride toothpastes.

Azer and colleagues used a nanometer scale - the equivalent
of one over a billionth of a meter — to measure the hardness
and elasticity of tooth enamel both before and after
laboratory exposures to over-the-counter teeth bleaching
solutions.

The researchers exposed 50 human tooth samples to 2 types
of whitening strip and 3 types of nightguard home bleaching
systems,

Ten tooth samples each underwent bleaching regimens according
to either the 3-week or 10-day manufacturer recommended
treatment protocol. The 5 remaining tooth samples served as
unbleached “controls.”

Compared with before bleaching and versus unbleached controls,
the bleached enamel showed significant decreases in hardness
on the nanometer scale, the investigators report in the Journal
of Dentistry.

The researchers also observed a significant decrease in enamel
elasticity in most bleached tooth samples compared with
unbleached controls.

More study into the long term effects of bleaching agents and
remineralization of tooth enamel would be worthwhile, the
researchers conclude.

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Imaging can predict brain tumor mortality

ANN ARBOR, Mich. — U.S. cancer scientists say they have
created an imaging technique that predicts brain tumor
mortality by analyzing changes in a tumor’s blood flow.
The technique created by researchers at the University of
Michigan Comprehensive Cancer Center uses a standard magnetic
resonance imaging protocol to monitor changes over time in
tumor blood volume within individual voxels — three-
dimensional analogues of pixels — rather than a composite
view of average change within the tumor. That “parametric
response map” allows scientists to see specific areas in
which tumor blood volume increased or decreased, that may
have canceled each other when looking at the changes as an
average. “What we have potentially is a generalized
analytical approach that we can use to quantify treatment
intervention in patients,” said study author Professor Brian
Ross. Assistant Professor Craig Galban added: “We’re seeing
treatment response earlier into the treatment, and responses
that couldn’t be detected at all looking at average changes.
We could detect this after just one week, which is amazing
for brain tumors.” The research is reported in the advance
online edition of the journal Nature Medicine.
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New leukemia biomarker is discovered

SAN DIEGO — U.S. cancer scientists say they’ve discovered a
potential new biomarker that can predict the aggressiveness
of chronic lymphocytic leukemia. Scientists at the University
of California-San Diego and the university’s Moores Cancer
Center said they determined high blood levels of a particular
enzyme — PDE7B — are an indicator that chronic lymphocytic
leukemia, the most common form of adult leukemia, will be
aggressive and in need of immediate treatment. “We found that
individuals with high levels really had worse disease and
showed that PDE7B expression had predictive value relative to
other currently available markers for disease severity and
progression,” said Dr. Paul Insel, who led the study. “In
some cases, the level of PDE7B expression provided prognostic
information that was additive to existing markers.” Insel
said the findings suggest PDE7B has a role in prognosis and
could also be a good drug target because it reflects part
of the biology of the disease. The research that included
Laura Rassenti, Minya Pu, Fiona Murray, Joan Kanter, Andrew
Greaves and Karen Messer was presented during the weekend
in Denver at the annual meeting of the American Association
for Cancer Research.
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Chemical stops radiation-caused leukemia

DENVER — U.S. researchers say they have determined treatment
with biphosphonates could prevent radiation-induced leukemia.
Alexandra Miller, a senior scientist at the U.S. Armed Forces
Radiobiology Research Institute, said her research is
designed to help military and space agency personnel, who
are more likely to be exposed to risky levels of radiation
than the general population. However, she said the research
could have applications for civilian populations as well.
“It is possible, although not yet proven, that the compound
we studied could have a general effect on leukemia associated
with causes other than radiation, such as age, which is much
more common,” said Miller. The study’s findings were to be
presented in Denver this week during the annual meeting of
the American Association for Cancer Research.

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Liver transplants studied in older people

HALLE, Germany — German scientists say they have determined
the reason transplanted liver cells don’t proliferate as well
in older recipients as they do in younger ones. Researchers
at Germany’s Martin Luther University said they determined
that while the age of the donor makes no difference, the age
of the recipient is significantly important — and many
humans requiring liver transplantation are older. The German
study conducted in rats found that older rats had a repop-
ulation rate of only 2 percent, 10 times less than that seen
in younger ones. Furthermore, the researchers found trans-
planted cells worked equally well in the old and young
animals, as measured by glycogen storage, but the younger
animals had significantly higher levels of a growth factor
needed for proliferation. Peggy Stock, a post doctoral
fellow, said the new study is the first to offer a possible
mechanism for the failure of transplanted hepatocytes to
proliferate in many human patients and it is also the first
to suggest a way to compensate for the problem. Stock re-
ported the study Sunday in New Orleans during Experimental
Biology 2009.

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FDA warns against some dietary supplements

WASHINGTON — The U.S. Food and Drug Administration is
warning against consuming several dietary supplements dis-
tributed by Universal ABC Beauty Supply International Inc.
The FDA said it advised the Brooklyn, N.Y., company that lab
analyses of the dietary supplements showed they contain
undeclared Sibutramine, an FDA-approved drug used as an
appetite suppressant for weight loss. The FDA said it has
not approved the products, therefore the safety and effective-
ness of the products is unknown, posing a threat to consumers
because Sibutramine is known to substantially increase blood
pressure and/or pulse rate in some patients. It might also
present a significant risk for patients with a history of
coronary artery disease, congestive heart failure, arrhyth-
mias or stroke, the federal agency said. Consumers with
questions can contact the company at 718-891-6888. A list of
the recalled products and other information is available at
http://www.fda.gov/oc/po/firmrecalls/universalabc04_09.html.

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Stem cells can help heal diabetic ulcers

BRISTOL, England — British medical scientists say they’ve
discovered human fetal stem cells can effectively heal back
leg ischemic ulcers in a model of type 1 diabetes. The
University of Bristol researchers said they also found the
culture in which the stem cells had been grown mimicked the
wound-healing ability of the cells. That, they said, suggests
the culture could be used as a “factory” of wound-healing
substances or the active ingredients in the culture could be
used instead, thereby avoiding the ethical concerns of using
human fetal stem cells. The scientists said diabetic patients
with ischemic foot ulcers have the worst outcome of all
chronic skin wounds. Ischemia occurs when blood supply is
greatly reduced or stopped. The researchers led by Professor
Paolo Madeddu found fetal stem cells accelerate the closure
of ischemic diabetic ulcers, while stem cells from blood of
adult donors are ineffective. “This is the first study to
demonstrate the healing capacity of local therapy with …
stem cells in a model of diabetic ischemic foot ulcer,” said
Madeddu. “The fetus-derived cells would be difficult to
obtain for therapeutic applications. However, the finding
that conditioned culture is also effective in stimulating
wound healing may have important implications for the cure
of the ischemic complications of diabetes.” The study
appeared ahead of print in the April 2 online issue of the
journal Circulation Research.

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