Medicine: Urea for Teeth

If the experiments of Dr. Robert Marshall Stephan of the University of Illinois are borne out during the next few years, they may help to send the dentist’s drill the way of blacksmith tools. Last week in Science, Dr. Stephan announced that he had found a neutralizer for tooth decay: urea.

Nobody knows exactly why teeth decay. Dentists generally agree on one clue to the mystery: certain acid-forming bacteria, such as lactobacilli, grow on tooth enamel, ferment crumbs of sweet and starchy foods which lodge in tooth crevices. The acid thus formed dissolves calcium in the teeth, causes cavities.

Like sweat and urine, saliva contains urea, a nitrogen compound. Dr. Stephan found that two groups of antagonistic bacteria flourish in saliva: 1) the destructive lactobacilli; 2) harmless germs of the staphylococcus family. By brewing an enzyme called urease. the staphylococci split up urea in the saliva into an ammonium compound, which neutralizes the erosive acid. Dr. Stephan’s conclusion: teeth may decay when the saliva does not contain enough urea, or when the staphylococci are sluggish.

He had a hunch that a way to save teeth from decay might be to encourage the staphylococci by giving them an extra amount of urea to work on. So he made up a mouthwash of carbamide (synthetic urea crystals). The crystals are colorless and odorless, taste cool and salty. He gave the mouthwash to 100 patients to use on their toothbrushes, found that an increased amount of calcium was deposited on their teeth.