The longer the bleaching time, the faster the bleaching effect -- and the greater the tooth sensitivity, according to a new study in the Journal of the American Dental Association (October 2010, Vol. 141:10, pp.1213-1220).
The application time for 10% carbamide peroxide (CP) with a tray for at-home bleaching is typically between four and eight hours, a team of Brazilian researchers noted. But they wanted to compare the bleaching effectiveness and tooth sensitivity associated with the traditional eight-hour night guard vital bleaching with 10% CP gel with the effectiveness and sensitivity associated with shorter application times.
They recruited 60 patients and categorized each of them into one of four groups. All participants used 10% CP in a bleaching tray. The daily application times were 15 minutes, 30 minutes, one hour, or eight hours. Participants bleached their teeth for 16 days; those who were not satisfied with the results extended the bleaching time until they were satisfied.
Patients recorded their tooth sensitivity on a 0 to 4 scale. The researchers used a digital spectrophotometer and shade guide to measure the shade changes.
Participants in the one- and eight-hour groups bleached their teeth for 18 and 16 days, respectively (p > 0.05); statistically longer periods were required for participants in the other two groups (p < 0.001) to be satisfied with the results. Participants' tooth sensitivity ratings were similar for the 15-minute, 30-minute, and one-hour application times (p > 0.05) and statistically lower than those in the eight-hour group.
"The results of this study show that although the traditional eight-hour application time yielded the fastest bleaching results, participants who underwent it reported higher levels of tooth sensitivity after 16 days of treatment," the researchers noted. The one-hour group most closely resembled the eight-hour group in terms of bleaching speed, and also yielded low tooth sensitivity, they added.
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