Tracking more than 800 patients, investigators found that while dental implants fail in 8.4% of patients prescribed penicillin, that figure shoots up to more than 17% among those given a different antibiotic.

“Dental implants fail at a very low rate,” said study lead author Dr. Zahra Bagheri, a clinical assistant professor at New York University College of Dentistry. “But implant failure can occur when the body interprets the implant as a foreign body and tries to get rid of it.”

To prevent this from happening, amoxicillin — a form of penicillin — is prescribed because “it is effective on most bacteria causing infection in the mouth,” she explained.

However, patients who are allergic to penicillin could experience a “physical reaction of the body that can potentially be life-threatening,” Bagheri noted.

In the United States, about 1 in 10 patients reports having such an allergy to their dentist, the study authors said.

Yet they also point to prior research suggesting that only about 1% of Americans actually have a true penicillin allergy.

Why the discrepancy? On one hand, almost half of patients who are diagnosed with a childhood allergy to penicillin “grow out of it as they get older,” said Bagheri.

And on the other hand, relatively minor — and even common — reactions to penicillin are often misinterpreted as a sign of an allergy.

Bagheri offered the example of “a patient who feels nauseous after taking penicillin [and] may express to their doctor that they’re allergic, without having taken a test and knowing for certain if the reaction was due to an allergy or not.”

Many dentists take the patient’s word and look for alternative medications, Bagheri said.

Dental implant surgery restores a missing tooth or teeth with an artificial device. The procedure can be time-consuming and costly, with a failed implant requiring additional surgical procedures.

To see if the type of antibiotic given to dental implant patients affects the failure rate, Bagheri’s team focused on 838 patients. A little more than half (434) said they had an allergy to penicillin.

None underwent testing to confirm their reported allergy. Instead, they were all given a different antibiotic. Alternative options included clindamycin, azithromycin, ciprofloxacin and metronidazole.

By contrast, all the patients in the nonallergy group were given amoxicillin.

The researchers reported that dental implants were successful in about 92% of patients prescribed amoxicillin.

But that success rate dropped to about 80% among those given clindamycin, and less than 70% among those prescribed azithromycin. When averaged out among all the nonpenicillin antibiotic options prescribed, the success rate hovered at around 83%.

Also, any dental failure cases occurred within six months post-procedure for the allergic group, compared with more than a year out for the others.

“At this stage, we don’t know if the failure is due to the patients being unable to take penicillin, and therefore being more prone to infection, or if there’s something else at play,” Bagheri said. “Future studies can help further clarify this relationship.”

But she suggested that patients who suspect a penicillin allergy should get tested to see if that’s truly the case.

“Our study suggests that if the patient is not truly allergic to penicillin, they may benefit from taking the [most] effective medication to reduce their risk of implant failure,” Bagheri explained.

The study results were recently published in the journal Clinical Implant Dentistry and Related Research.

Dr. Alan Gluskin, immediate past president of the American Association of Endodontists, seconded that thought.

“I think that’s a very reasonable — in fact the most reasonable — approach to this,” said Gluskin, who is also vice chair of endodontics at the University of the Pacific’s School of Dentistry in San Francisco.

“We don’t know if this is true yet,” he cautioned. “And we don’t know if this is about certain ecologies in people’s mouths — different bacterial counts and species in the mouth that might respond better to some antibiotics than others. More research is needed to find out.

“But if meaningful research provides good evidence that that is the case, then, of course, we should feel compelled to find out if and when someone really has an allergy and make decisions based on that testing and the science,” Gluskin said.

More information

There’s more on dental implants at the U.S. Food and Drug Administration.

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