Antibiotics that dentists prescribe are unnecessary 81% of the time

The findings are important because dentists are responsible for 10% of all antibiotic prescriptions written in the United States.

Antibiotics prescribed when not warranted expose patients to the risk of side effects unnecessarily and also contribute to the problem of antibiotic resistance -- bacteria evolving to make the drugs ineffective.

Antibiotics are recommended as a prophylactic prior to some dental procedures for patients with certain types of heart conditions.

Researchers including Jessina McGregor of Oregon State University used a national health care claims database to examine nearly 170,000 dentist-written antibiotic prescriptions from 2011 to 2015.

The prescriptions involved more than 90,000 patients, 57 percent female, with a median age of 63.

Greater than 90 percent of the patients underwent a procedure that possibly warranted taking an antibiotic ahead of time. However, less than 21 percent of those people had a cardiac condition that made an antibiotic prescription recommended under medical guidelines.

"Preventive antibiotics in these patients gave them risks that outweighed the benefits," said McGregor, an associate professor in the OSU College of Pharmacy.

Led by corresponding author Katie Suda of the University of Illinois-Chicago, the researchers also looked at the prescriptions regionally and found unnecessary prescriptions to be most prevalent, on a percentage basis, in the West; 11,601 of the 13,735 prescriptions written, or 85%, were out of sync with the guidelines.

The other regional percentages were 78% for the Northeast, 83% for the Midwest, and 80% for the South.

Eighty-two percent of the unnecessary prescriptions were written in urban population centers, 79% in rural areas.

Among patients who filled prescriptions for unnecessary antibiotics, clindamycin was the most common drug, and joint implants were the most typical reason they were prescribed.

"Dental providers are very thoughtful when they develop care plans for their patients and there are many factors that inform dentists' recommendations, but this study shows that there is an opportunity for dentists to reevaluate if necessary," said Susan Rowan of the Illinois-Chicago College of Dentistry. "I think dental providers should view this study, which is the first to look at preventive antibiotic prescribing for dental procedures, as a powerful call to action, not a rebuke."

The study was limited to patients with commercial dental insurance and the analysis used a broad definition of high-risk cardiac patients, suggesting the findings may underestimate the unnecessary prescribing of antibiotics.

Five other researchers from Illinois-Chicago and one from Northwestern University also collaborated on the study, which was funded by the Agency for Healthcare Research and Quality.