A study comparing antimicrobial peptides, or AMPs, a group of small proteins that occur naturally in human saliva and act like antibiotics against oral bacteria, could lead to new ways to screen children for risk of tooth decay and protect them against this common, chronic problem.

The study, "Salivary Antimicrobial Peptide Expression and Dental Caries Experience in Children," published in the September 2005 issue of the journal Antimicrobial Agents and Chemotherapy, involved oral examinations performed on 149 middle school children.

Researchers at the University of Washington in Seattle set out to determine a possible correlation between dental caries (tooth decay) prevalence in children and salivary concentrations of three types of antimicrobial peptides.

Antimicrobial peptides, or AMPs, are one of the body's natural defenses against bacteria, targeting and killing invading microbes.

Results found that children with no tooth decay had higher levels of one particular type of AMP ( alpha-defensin) than children with tooth decay. Therefore, low levels of alpha-defensin might be a biological factor that contributes to making some children naturally more susceptible to tooth decay.

"We know that sometimes children who take good care of their teeth still get cavities, and that other children, who don't take care of their teeth, don't get cavities, so dental researchers think that some people have better natural defenses against tooth decay than others," said Dr. Beverly Dale, professor of oral biology at the University of Washington and corresponding author of the study.

Dental caries is one of the most common of all disorders - second only to the common cold - and is a major worldwide oral disease problem in children. While tooth decay results from a bacterial infection, it is also heavily influenced by diet and oral hygiene. Bacteria that are normally present in the mouth convert foods, especially sugar and starch, into acids. These acids then combine with bacteria, food debris and saliva to form a sticky substance called plaque that sticks to teeth. The acids in plaque dissolve the surface of the tooth and create holes, called cavities.

Dale said that future studies could lead to a simple test for clinical evaluation of tooth decay risk and to the development of new ways to use these peptides for therapeutic treatment.

The study was funded by the National Institute of Dental and Craniofacial Research, part of the National Institutes of Health.

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