At-home teeth whitening systems are the new craze. A scroll through your social media shows everything from “laser activated” gels to charcoal toothpastes. With the flood of new whitening systems into the market, clinicians have to choose which system to invest in.
Mode of action
Hydrogen peroxide (usually 2-6%) and carbamide peroxide (10-16%) gels are the most common active agents for clinician prescribed take home whitening systems. Over the years, carbamide peroxide has shown less tooth sensitivity and gingival irritation than hydrogen peroxide. Carbamide peroxide decomposes to produce hydrogen peroxide and urea during use. Hydrogen peroxide further breaks down into water, oxygen and free radicals, and it is these free radicals that provide the “whitening” effect on the tooth. The second product of the initial decomposition – urea, increases the pH of the solution, by producing ammonia and carbon dioxide. This now basic solution, further aids the generation of free radicals, pushing the whitening action of the solution forward.
Prescription
Throughout the world and with different manufactures, the recommended prescription of carbamide peroxide gels varies. Usually the solution is made with a 10-16% carbamide peroxide concentration, and its recommended use ranges from 1-10 hours a day for up to 21 days (with lower concentrations needing longer application times).
However, recent research has shown that carbamide peroxide degrades more than 3 times faster in the first hour, compared to any subsequent hour afterwards. Following the first hour, the reaction significantly slows down and its benefits toward whitening teeth are minimal. So applying a carbamide peroxide gel for longer than 90 minutes a day doesn’t award any benefits, but does increase the chances of tooth sensitivity and gingival irritation.
Stability of effects in the long-term
Patients, who ask about teeth whitening, are looking for lightening their teeth and achieving uniformity amongst the dental arches themselves. Teeth naturally have different shades due to changes of enamel and dentin thicknesses along the arch. Before treatment, the lightest teeth are known to be mandibular/maxillary incisors, followed by mandibular/maxillary premolars, with maxillary/mandibular canines being the “darkest” teeth. How does carbamide peroxide’s effect stand the test of time, and how do its effects vary amongst individual teeth?
95 patients were followed for 3.5 years, after a 4-week application of 16% carbamide peroxide for 90 minutes a day. One week after the treatment, all teeth were significantly lighter compared to before the treatment (not a surprise), and lightness was seen to equalize between the different teeth groups at 6 months.
Controlling for staining habits (such as smoking, drinking wine and coffee), the effects of the treatment remained for 30 months following the end of treatment, at which time is started to diminish. When the effects of the treatment started to wear, the discrepancy between the lightness of different teeth groups also began to return.
Carbamide peroxide between 10-16% concentration can give our patients safe, predictable and stable results for a long period of time (if staining substances are controlled).