That doesn't prove that the drug caused those problems. More studies are needed, and the researchers aren't calling for any changes in amoxicillin's use.
"If the choice is hearing loss ... or the possible risk of minor cosmetic disappointment, there is little doubt of what will happen," states a related editorial.
The study and editorial appear in the Archives of Pediatrics and Adolescent Medicine.
The study included 579 children. Their amoxicillin use was noted every three months during their first year of life. When the kids were about 9 years old, their permanent teeth were checked for fluorosis.
Fluorosis is one of the most common problems in the development of tooth enamel. It happens when teeth are exposed to too much fluoride when tooth enamel is forming. Symptoms include barely noticeable white flecks, pits, or brown stains on teeth.
Kids who had taken amoxicillin between ages 3 and 6 months were about twice as likely to have fluorosis, says researcher Liang Hong, DDS, MS, PhD, and colleagues.
Hong worked on the study while at the University of Iowa's departments of preventive and community dentistry. Hong is now with the University of Missouri-Kansas City's department of dental public health and behavioral science.
More Work Needed
Hong's team took other possible influences into account, but their finding didn't change. They note that some other antibiotics (including tetracylines) are known to influence tooth development.
Still, patterns can be misleading. That's why the researchers call for more studies to see if amoxicillin can cause fluorosis.
Editorialist Paul Casamassimo, DDS, MS, agrees that more research is needed. Such associations should be viewed "with a cautious but open eye," he writes.
Casamassimo works at Ohio State University's College of Dentistry and Columbus Children's Hospital. He didn't work on Hong's study.
Best Course of Action
"As a clinician, I would welcome an explanation that would help parents' guilt, exonerate both medical and dental providers, and, most importantly, help me to prevent a needless occurrence of fluorosis in my patients," writes Casamassimo.
"Until that time, the best course of action may be what both the medical and dental communities have advocated for a long time -- careful, thoughtful, and appropriate use of both fluoride and antibiotics," he continues.