People with replacement joints have long been told to take antibiotics before having even routine dental treatment. But that advice isn’t as widely supported as it once was. (Edward Olive/Getty Images/iStock)

Joint replacement is among the most reliable of common surgeries. Since getting my left hip replaced seven years ago and my right hip a couple of years after that — and following up with physical therapy so I could relearn how to walk like a regular person — I hardly ever think about the fact that I have metal and plastic where bone used to be.

Except when I go to the dentist.

For years, people with artificial joints have been told they should take a single large dose of an antibiotic one hour before any dental treatment, whether a routine teeth cleaning or an invasive root canal procedure.

The reasoning is simple: Your mouth is filled with bacteria, and when the dentist or hygienist starts poking around, some of those bacteria can get into your bloodstream. If they travel to an artificial joint and take up residence, they can form a biofilm (in common language, a kind of slime) on the metal or plastic parts. Biofilms are very tenacious and can ruin the joint, forcing a new surgery to replace it, says Helen Boucher, a professor of infectious diseases at Tufts Medical Center in Boston. Taking a dose of antibiotics before dental treatment is supposed to kill off any stray bacteria, reducing the chances of this unpleasant outcome.

That’s the idea, anyway. But surgeons do not all offer the same advice. The orthopedist who replaced my left hip told me that I should take a pre-dental antibiotic for the first two years after my surgery but after that it was fine to stop, provided all was well with the new hip. He moved from the area, and my right hip was replaced by another surgeon in the same practice. His recommendation: Take an antibiotic before you go to the dentist for the rest of your life.

Current guidelines from the American Academy of Orthopaedic Surgeons say that orthopedists “might consider discontinuing” routine prescription of antibiotics before dental procedures. The wording may be judicious, but it’s unhelpful to someone trying to reach a thoughtful decision.

My original concern was that taking antibiotics unnecessarily contributes to the emergence of resistant strains of bacteria, but I learned that there are more immediate risks. Occasionally, people die after an allergic reaction to an antibiotic. There are also cases, Boucher says, when a single prophylactic antibiotic dose disturbs a person’s intestinal bacteria so much that they succumb to a fatal infection by the notoriously hard-to-treat bacterium Clostridium difficile .

Heart issues, too

It’s not just people with artificial joints for whom prophylactic antibiotics pose a quandary. For decades, the American Heart Association told people with heart murmurs caused by congenital or other problems with their heart valves — such people face a greater risk of a devastating and potentially heart infection called infective endocarditis, or IE — to take antibiotics before they see the dentist. Similar advice was given to anyone with an artificial heart valve.

Yet it’s far from clear that prophylactic doses of antibiotics are necessary for all these heart patients. Some cases of IE are definitely associated with bacteria that live in the mouth, says Ann Bolger, a cardiologist at the University of California at San Francisco School of Medicine. But “we cannot connect the dots — we cannot associate any given episode [of dental treatment] with infection down the road.”

Despite the connection of IE to oral bacteria, the American Heart Association changed its guidelines for dental doses significantly in 2007, reducing the population for which prophylaxis is recommended (among them people with artificial valves, a history of IE and certain types of heart disease).

“IE is a terrible thing,” Bolger says. “If I thought prophylactic antibiotics would prevent [one patient from getting IE], I would drive the truck to their house” to deliver the drugs.

Thomas Sollecito of the University of Pennsylvania’s School of Dental Medicine chaired a 2014 American Dental Association panel that reviewed studies comparing the dental histories of people who had contracted infections of artificial joints with those of similar people with replaced joints who remained infection-free. Bottom line: There was no statistical connection between dental visits and subsequent joint infections, regardless of whether patients had taken antibiotics.

In 2015, the ADA revised its clinical practice guidelines to say that the group no longer recommends prophylactic antibiotics for patients — like me — with replacement joints. “ The current best evidence failed to demonstrate an association between dental procedures and prosthetic joint infection,” the ADA noted.

Of course, infected joints and cases of IE still happen. What causes these infections? Research shows that oral bacteria get into your bloodstream all the time — not just because of your dentist, but also when you brush or floss, even when you simply chew food. Your immune system typically mops up the intruders, but there’s always the chance a few bacteria will get away, with potentially serious consequences.

Because you brush and floss every day — you do, right? — it’s far more likely for those routine actions to be the source of an infection than the occasional visit to the dentist. Bolger and Sollecito say that the first line of defense for patients in at-risk groups is good dental hygiene. Of course, flossing can make your gums bleed, especially if you haven’t been doing it regularly. There’s been a debate recently about the lack of research regarding its effectiveness, but most dentists believe that daily flossing improves gum health and reduces bleeding, minimizing the risk of sending nasty bacteria into your bloodstream.

Bolger says that she continues to recommend antibiotic prophylaxis for heart patients covered in the current AHA guidelines “not because I believe there is data that it works, but [because] for those people the [effect] of infection is so overwhelming that it’s too far to go to change the 50-year-old recommendation.” She points out that in the United Kingdom, prophylactic antibiotics have not been recommended for heart patients since 2008.

Doctors’ skepticism

If the weight of evidence points to discontinuing routine prophylaxis, why do many surgeons and dentists continue to recommend it?

One factor is that old habits die hard. The professional organizations — AHA, ADA, AAOS — can issue guidelines, but they cannot tell their members what to do. Robert Quinn, head of orthopedic surgery at the University of Texas Health Science Center in San Antonio, is moderator of an AAOS panel that’s reviewing the 2015 ADA guidelines with a view to revising their own guidelines. He says his group’s conclusions, set to appear at the end of this year, are unlikely to be very different from what the ADA has suggested, but he acknowledges that “a lot of people who have been in practice for a while” tend to be skeptical of change. “There is a big push for evidence-based decisions,” he says, “but there is also pushback [based on long-standing practice]. We need to navigate thoughtfully.”

Bolger takes the same line: As health-care providers, she says, “our obligation is not to do useless and potentially harmful things, but it’s hard to challenge assumptions people have held for a long time.”

So where does that leave me, with my artificial hip joints and a long history of dental woes?

I was already leaning against taking antibiotics before routine dental cleanings, and talking with the experts gave me more confidence in that decision. But then fate threw up another challenge.

Just as I began working on this story, I developed an ache in a tooth with root-canal treatment and a crown dating back at least 25 years. There seemed to be some infection. It can be fixed, at the cost of several visits to different dentists over the next few months. Taking a series of single-dose antibiotics doesn’t seem like a good idea: Surely my gut won’t thank me, and it seems like just the sort of antibiotic use that contributes to the problem of resistance that everyone is concerned about. On the other hand, my tooth has an infection!

I dithered, and went to the endodontist without taking an antibiotic but with pills in hand, in case he refused to proceed unless I took my medicine. As it happened, he was well aware of the arguments against prophylactic antibiotics and not at all fazed by my preference to avoid them. I’ve seen him several times now, the tooth appears to be recovering and my hips are working just fine.

I’m not under any illusion that my personal actions will have great consequences for national policy on antibiotic use. As Quinn puts it, “bacterial resistance is a societal problem, not individual.” But I like to think I’m doing my bit. You’re welcome.