How often can you safely whiten your teeth?
It’s not fully clear, but once or twice a year seems to cause no problems, said Dr. Dan Nathanson, chair of the department of restorative sciences and biomaterials at the Boston University School of Dental Medicine.
“No one has shown categorically that there is a danger in doing it too much, but we are cautious. It’s probably not good to be a whitening addict,” he said.
The basic ingredient in tooth-whitening gels, whether administered in a dentist’s office or at home, is hydrogen peroxide, which penetrates both the porous enamel on the outside of the tooth and the inner layer of dentin, lightening the tooth as it goes.
Whitening does not seem to destroy either the enamel or the dentin. But all forms of bleaching can cause temporary tooth sensitivity.
There are some differences — including financial — between whitening done at home and that done at the dentist’s office. In the office, dentists use a stronger concentration of peroxide gel, 30 to 35 percent, and the procedure can run about $1,500 for three treatments.
With the middle-priced option, a dentist takes impressions of both upper and lower teeth, which costs about $800, and makes retainer-like arches. The patient fills the arches with gel and inserts them every night for a set number of days.
Over-the-counter whitening strips, which cost roughly $30, use the weakest concentrations of peroxide, but still “do a pretty good job,” said Nathanson.
But the strips only reach from one canine (“eye”) tooth to the other “and most people have bigger smiles than that,” though, said Dr. Howard Strassler, professor of operative dentistry at the University of Maryland Dental School.
And if your teeth aren’t perfectly straight, they may not bleach evenly.
What causes dark circles under the eyes, and what can you do about them?
Some people are born with a relatively deep hollow, or “tear trough,” in the corner of the eye near the nose, which can cast a shadow near the corner of the eye, said Dr. Sandy Tsao, a dermatologist at Massachusetts General Hospital in Boston.
Other people, particularly those of Mediterranean descent, are born with dark pigmentation in the dermis layer of the skin, “which creates a blue-black hue below the eyes,” she added.
Superficial blood vessels in the skin can also create “a dark cast in some individuals all of the time, particularly if they have sinus problems or other problems which increased venous pressure in the area,” said Dr. Bernard Cohen, a dermatologist at the Johns Hopkins School of Medicine.
Dark circles under the eyes, by the way, are different from saggy lower eyelids, or eye bags. The circles often get worse because of swelling when a person hasn’t slept.
Rubbing the eyes, as people with allergies often do, can also make things worse, because this thickens and inflames the skin on eyelids.
Concealers containing green cover up the reddish hue from excess blood vessels, while yellow can cover dark pigmentation, said Tsao.
If the circles really bother you, you can try laser treatments. This usually involves both a Q-switched ruby laser to get rid of the dark pigmentation and a pulsed dye laser for the blood vessels.
Although the procedure is safe, Tsao said, it’s not cheap — about $1,500 for the three treatments — and is not covered by insurance.
Source: Baltimore Sun