Between 1837 and 1838 they identified, analyzed, and classified many of the constituents and degradation products of urine, including urea (carbamide), uric acid, allantoin, and uramil.
Urea or carbamide [CO NH2 2] is a crystalline compound that is formed as the end product of the metabolism of protein and excreted in the urine of mammals.
Urea (also called carbamide) and melamine (also called cyanuramide) are both colourless, crystalline solids containing an amino group (NH2).
Go Smile, developed by Dr. Jonathan Levine for the Esthetic Whitening Centers of Manhattan, releases an active liquid carbamide peroxide gel -- a whitening agent -- through a tiny vacuum ampule.
Try telling that to Dale Michele Asti, a boutique owner in Beverly Hills who uses her 22percentt carbamide peroxide bleaching tray several times a week.
The peroxides used in tooth bleach, hydrogen peroxide and carbamide peroxide (which contains hydrogen peroxide) produce free radicals that can damage cells of the gums or pulp inside teeth, said Dr. Yiming Li, the director of the Center for Dental Research at Loma Linda University School of Dentistry in California.
Fifteen years ago the first trays dispensed by dentists used gels that were 10percentt carbamide peroxide, equivalent to about 31/3percentt hydrogen peroxide.
Today, Discus Dental Nite White ACP Deluxe Kit, dispensed by dentists, contains 22percentt carbamide peroxide gel (about 7percentt hydrogen peroxide).
"Once you get above 15percentt carbamide, you are pushing the envelope," Dr. Haywood said.
The Minute White Laser Speed Tooth Whitening System, sold on the QVC shopping channel, includes a 22percentt carbamide peroxide whitener.
