One of the most widely used pediatric antibiotics, Amoxil (amoxicillin), may interfere with the complete development of tooth enamel, researchers here say.

The findings were based on a longitudinal study of the effects of fluoride on tooth development, and they “highlight the need to use antibiotics judiciously, particularly during infancy,” reported Liang Hong, DDS, Ph.D., and colleagues at the University of Iowa.

But, they noted in the October issue of Archives of Pediatric and Adolescent Medicine, the study has several limitations - including a relative lack of children not treated with the antibiotic - and requires further research before it can be considered conclusive.

The association between Amoxil and fluorosis on some early-erupting permanent teeth “holds implications for both dental and medical practice if it holds up,” said Paul Casamassimo, DDS, of the Ohio State University College of Dentistry in Columbus.

The finding by Dr. Hong and colleagues may be “another clue as to why some children get fluorosis and others do not,” Dr. Casamassimo said in an accompanying editorial, “but much more study remains to be done before we put away the prescription pads or clear the pharmacy shelves.”

Fluorosis - incomplete development of tooth enamel caused by high doses of fluoride - is one of the most common forms of developmental enamel defects, but it is not fully understood, Dr. Casamassimo said.

In the Iowa Fluoride Study, Dr. Hong and colleagues enrolled 1,390 participants at birth from eight Iowa hospitals. Of those, 579 had an examination of early-erupting permanent teeth at approximately the age of nine; their teeth were assessed for fluorosis using the Fluoride Risk Index.

From birth to 32 months, the children had been followed by regular questionnaires, filled out by their parents, to assess fluoride intake and the use of Amoxil (also sold under the brand names Trimox and Wymox).

The study found that:

 
• By 12 months of age, 75% of the children had been given Amoxil and by 32 months, 91% had been treated with it.  
• When they were examined at age nine, 24% had fluorosis on both maxillary central incisors.  
• Amoxil use between the ages of three and six months significantly increased the risk of fluorosis on the maxillary central incisors. The relative risk was 2.04, with a 95% confidence interval ranging from 1.49 to 2.78.  
• After adjusting for fluoride intake and otitis media, the risk of fluorosis on the maxillary central incisors remained significant. The relative risk became 2.04, with a 95% confidence interval ranging from 1.2 to 2.78.

Dr. Hong and colleagues cautioned that the study has several limitations, including the fact that very few of the children in the study - just 8.2% by 32 months - had not been treated with Amoxil at least once.

Also, much of the data come from questionnaires, without direct verification.

The researchers suggested that, among other things, animal studies be undertaken to see if the effect can replicated experimentally.

Fluorosis affected children long before Amoxil, Dr. Casamassimo said, “which raises some skepticism as to the validity of these findings.”

He noted that the first six months of life are a period in which children battle numerous infections, often with a high fever, so that the combination of fever and high fluoride might actually be the culprit, with Amoxil as a confounding factor.

Even if the link is substantiated, he said, it might not have much effect on prescribing patterns, which have already begin to change in favor of a more limited use of antibiotics.

Also, it’s unlikely that the risk of fluorosis in the future would deter a parent from using an antibiotic to cure otitis media in the present, he said: “If the choice is hearing loss and its sequelae or the possible risk of minor cosmetic disappointment, there is little doubt of what will happen.”