London: Fluoride in some toothpaste and mouthwash, believed to prevent tooth decay, may actually be ineffective as the so-called protective layer it forms is too thin, scientists say.
Experimental physicist Frank Müller and colleagues from Saarland University in Germany point out that tooth decay was a major public health problem worldwide, the journal Langmuir reports.
In the US, consumers spend more than $50 billion every year on treating cavities.
Scientists have known that fluoride makes enamel - the hard white substance covering the surface of teeth - more resistant to decay, said a Saarland university statement.
New research found that the fluorapatite layer formed in this way was only six nanometers thick.
It would take almost 10,000 such layers to span the width of a human hair. That`s between 10 to 100 times thinner than what previous studies indicated.