A 5% potassium nitrate and 2% sodium fluoride solution worked better than a placebo in reducing tooth sensitivity during bleaching, without interfering with the whitening, in a study published in this month's Journal of the American Dental Association (Vol. 140; 10, pp: 1245-1251).
Researchers from the universities of Estadual de Ponta Grossa and Oeste de Santa Catarina wondered if sodium fluoride would interfere with the whitening effects of bleach because of its mechanism of action: the fluoride blocks dentin tubules, keeping the bleach away from the pulp. (Potassium nitrate, on the other hand, works by calming nerve signals, so it wasn't expected to interfere with the bleach.)
The researchers applied the desensitizing gel to the teeth of 15 subjects and a placebo gel to the teeth of 15 other subjects. Then they bleached the subjects’ teeth with 35% hydrogen peroxide gel and repeated the procedure a week later.
They found that the subjects’ teeth got just as white regardless of whether they were treated with the placebo or the real desensitizing gel. They hypothesized that the peroxide molecules were small enough to slip between tubules.
Seven subjects who were treated with the real desensitizer reported that their teeth hurt the day of the bleaching, while 13 of those who only got the placebo felt the pain, a statistically significant difference (p < .05).
