WebMD Medical
News
Do tooth-whitening products
lead to oral
cancer? New research suggests that it's certainly possible and a
question that's worth further investigation.
|
Georgetown University Hospital researchers say the active
ingredient in these popular whiteners -- available at a dentist's office
or in over-the-counter kits -- may be the reason why two patients with
no other identifiable risk factors developed advanced tongue cancer
while in their 20s.
But when these patients don't have a
significant history of this use, you start to wonder what else they are
being exposed to," says Bruce Davidson, MD, FACS, chairman of
otolaryngology-head and neck surgery at the Washington, D.C., hospital.
Free Radical Damage Suspected
His suspicion: The hydrogen peroxide in
the gels dentists apply to whiten teeth and in over-the-counter
self-application bleaching kits to whiten teeth. Products are often
labeled to contain carbamide peroxide, one-third of which is composed of
hydrogen peroxide. In addition, when used as a whitener, carbamide
peroxide changes into hydrogen peroxide, say the researchers.
In animal studies, peroxide has been
shown to promote the growth of cancerous tumors inside the cheeks of
rodents and cause gastrointestinal cancers when ingested. No tests
have been done on humans. Specifically, the theory is that
when hydrogen peroxide leaks from trays containing the whitening gel
onto surrounding areas inside the mouth, it triggers the release of
cancer-causing "free radical" cells.
"Further testing is obviously required
before we can be certain of a link, but people should be aware there is
a possible link," Davidson tells WebMD. "If I was in the market for
teeth whitening, I'd think twice about it. I make my career in treating
head and neck cancers, so I'm also not going to go out and chew tobacco
and smoke cigarettes, either."
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No Additional Risks Noted
Research he presented Saturday at the 6th
International Conference on Head and Neck Cancer documents two patients
who developed advanced tongue cancer decades earlier than usual, after
repeated use of tooth-whitening products. Both patients were occasional
drinkers, having no more than three drinks a week. One was a light
smoker, the other didn't smoke. They are among 19 oral cancer patients
of all ages studied by Davidson's team of head and neck cancer surgeons.
A middle-aged man who also developed tongue cancer used tooth-whitening
polish, but the other patients didn't use bleaching products. Among six
patients who developed oral cancer before age 40, two used tooth
whiteners, and both had more advanced cancer than the others, despite
not smoking or drinking any more heavily.
The Reaction?
Terry Day, MD, director of head and neck
oncologic surgery at Hollings Cancer Center at the Medical University of
South Carolina and a spokesman for the American
Academy of Otolaryngology-Head and Neck Surgery, says the study deserves
notice because it points to why there's a growing trend in young people
developing oral cancers -- especially affecting the tongue -- without a
long-term history of those damaging vices.
"About 10% to 15% of oral and head and
neck cancers do not seem to be related to tobacco and/or alcohol," he
tells WebMD. "Other considerations still under investigation include
genetic factors, the human papillomavirus (which
causes genital warts), and nutrition factors. This study is
interesting in that it points to the possibility of another factor being
involved. "But due to the small size, it's a serious limitation to
whether or not you can say there's a relationship to teeth-whitening
agents and oral cancer."
Until now, there has been little research
on the long-term effects of tooth whiteners, and Davidson's study is
believed to be the first to examine the link between cancer and tooth
whiteners. Since they are considered "cosmetic" products, tooth
whiteners don't fall under FDA regulation. While dentists have used
these gels for some time, commercially available products have only been
available for several years, so their long-term effects haven't been
studied. American Dental Association spokesman David Sarrett, DMD, a
professor of dentistry at Virginia Commonwealth University, says there
is no evidence that when used as directed,
tooth whiteners increase cancer risk or cause other problems. But he
does acknowledge they are abused by some people.
"Some patients are what we call
'tooth-whitening junkies' who are not satisfied until their teeth are
snow white, and that's not achievable," he tells WebMD. "Even when using
an over-the-counter whitener, I also advise people to first consult with
their dentist, and always follow the product directions."
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Leakage a Problem
When whiteners are applied by a dentist,
which costs $200 or more, custom-fitted trays are used to hold the
gel, reducing risk of hydrogen peroxide leakage; with over-the-counter
products, the trays are usually not form-fitting. But even under
ideal conditions, reports Davidson, studies show that often less than
50% of the whitener is still in the trays one hour after application,
indicating a lot of leakage. Sarrett does caution against buying
tooth whitening products over the Internet -- for another reason.
"They may have the right ingredients, but because they don't balance
ingredients properly, they may not have the
right pH, as with gels used by dentists or from reputable companies," he
says. "It could be too acidic, which we know can damage tooth enamel."
SOURCES: The 6th International Conference
on Head and Neck Cancer, Washington, D.C., Aug. 7-11, 2004. Bruce J.
Davidson, MD, FACS, chairman, division of otolaryngology, Georgetown
University Hospital, Washington, D.C. Terry Day, MD, director, division
of head & neck oncologic surgery, Hollings Cancer Center; associate
professor, Medical University of South Carolina, Charleston. David
Sarrett, DMD, professor of dentistry and associate vice president of
health sciences, Virginia Commonwealth University, Richmond; member,
American Dental Association Council on Scientific Affairs.
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Updates
Is Teeth Whitening Addictive?
WebMD.com
raises the question of “whitening addiction,” citing those who have a
narcissistic compulsion to maintain their youth by overuse of tooth
whitening products, both OTC and professional. Signs of whitening abuse
include people who seek to get their teeth to a "Clorox white” shade
until their teeth are almost transparent, yet do not seem to realize
their teeth are already white. It is unlikely that damage to the surface
of the tooth will be caused before the sensitivity occurs. He
cautions against bleaching for people under age 18 as there is greater
opportunity for hypersensitivity. Dentists need to partner with
patients to set realistic expectations and avoid overuse of whitening
products.
"Bleachorexis" overwhitening their
teeth
ABC news reports that more people are using tooth bleaching – from over
the counter products – to dentist prescribed take home kits– to
in-office light activated whitening – to pursue a perfectly white smile.
As with many cosmetic trends, some “whitening junkies” are aiming for
an unnaturally white shade by overusing theproducts. Excessive use of
bleaching products can damage tooth structure and gums. Some overly
enthusiastic patients experience tooth sensitivity, blisters and
discoloration on teeth and gums. 4/05
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Effect of
bleaching on restorations—a systematic review
Existing literature
reveals that bleaching therapies may have a negative effect on physical
properties, marginal integrity, enamel and dentin bond strength, and
color of restorative materials as investigated in numerous in vitro
studies. However, there are no reports in literature indicating that
bleaching may exert a negative impact on existing restorations requiring
renewal of the restorations under clinical conditions.
Attin T, Effect of bleaching
on restorative materials and restorations—a systematic review
Dental Materials 2004; 20(9):852-861.]
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