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Question: I had a knee replacement two months ago at a hospital in Ontario and was provided with literature about what to expect and what to do after the surgery. Included in it was a caution to request an antibiotic prescription from my dentist for any dental procedures – including getting my teeth cleaned – for the rest of my life. The hospital literature said that without antibiotics, my new joint could become infected. But when I recently visited my dentist, he said antibiotics weren’t necessary for people with knee or hip implants. Who is right?

Answer: Your dentist is correct, according to the best available scientific evidence. But patients have good reason to be confused because of conflicting messages from different medical and dental associations in recent years.

It’s true our mouths are teeming with bacteria. So, there has long been a concern bacteria might enter the bloodstream during a dental procedure; simply cleaning the teeth can cause the gums to bleed.

It was feared bacteria could travel in the blood to the site of a prosthetic device – such as a knee or hip implant – and lead to an infection. If the infection eroded the bone around the implant, the patient may need another joint replacement operation.

The risk, however, is considered hypothetical, says Dr. Susan Sutherland, chief of dentistry at Sunnybrook Health Sciences Centre. There is no evidence directly linking dental procedures to implant infections.

Even so, many medical experts felt some precautions were needed.

Unfortunately, those good intentions led to a string of public health recommendations that were not grounded in good science.

It’s worthwhile reviewing the history of the various guidelines to see how they may have contributed to public confusion.

Back in 2003, the American Dental Association (ADA) and the American Academy of Orthopaedic Surgeons (AAOS) issued a joint statement, saying patients should take one dose of antibiotics an hour before dental procedures for the first two years after they received a knee or hip replacement. In Canada, the dental and orthopaedic associations adopted an identical approach.

Then in 2009, the AAOS, without the agreement of ADA, called for even stricter measures, saying joint-implant recipients should use antibiotics before every dental procedure for their rest of their lives.

Yet, at that same period of time, other medical professionals were openly critical of antibiotic prophylaxis – the practice of giving healthy people antibiotics to prevent a potential infection. In fact, the critics warned the overuse of antibiotics was contributing to the emergence of worrisome antibiotic-resistant strains of bacteria – a major public health threat.

So, the American dentists and orthopaedic surgeons decided, once again, to join forces to review the scientific literature. The reviewers found no direct evidence that dental procedures can lead to implant infections. But their final recommendations, published in 2012, were vaguely worded. They seemed to be neither for nor against antibiotic prophylaxis. Surgeons and dentists essentially had to decide for themselves what to recommend to their patients.

“The guidelines were ambiguous and really not helpful,” says Dr. Sutherland, who is the chair the Canadian Dental Association’s (CDA) committee on clinical and scientific affairs.

Indeed, the rather nebulous recommendations from the American groups led Canadian health professionals to chart their own course.

The Canadian Dental Association released last year a position statement that said: “Routine antibiotic prophylaxis is not indicated for dental patients with total joint replacements, nor for patients with orthopedic pins, plates and screws.”

The Canadian Orthopaedic Association (COA) is still in the process of reviewing the scientific literature and coming up with its own guidelines. “I think it is going to take us another year,” says Dennis Jeanes, the COA’s manager of communication and advocacy. But he indicates the COA reviewers will likely produce recommendations that are very similar to those already adopted by their dentistry counterparts.

Let’s recap where we currently stand. Canadian dentists now have clear guidelines from their national organization – and antibiotic prophylaxis is out. Orthopedic surgeons are still waiting for their recommendations, although they are probably headed in the same direction as the dentists.

I hope this helps explain why you received different advice from your dentist and the hospital where you got your new knee.

In the meantime, the scientific case against antibiotic prophylaxis continues to get stronger. One piece of evidence is particularly convincing: the bacteria in the mouth tend to be different than those associated with infections around implants.

“The organisms that are most responsible for early and late stage prosthetic joint infection are Staphylococcus aureus and coagulase-negative staphylococci, both uncommonly found in the oral cavity or outside their usual skin habitat,” according to a paper published in the Journal of Canadian Dental Association by Dr. Andrew Morris and Dr. Sandra Nelson [formerly Sandra Howie], who are researchers at Mount Sinai Hospital in Toronto.

The paper also contains a sobering statistic. Up to a million patients each year receive total joint replacements in the United States alone. (There are more than 93,000 knee and hip replacement operations performed in Canada annually.)

That’s a big number of additional people who would be taking antibiotics unnecessarily every time they had a dental appointment. It actually amounts to 2 tonnes of antibiotics every 6 to 12 months, further fueling the growth of resistance bacteria – without any proven benefit to patients.

“We use so many antibiotics that are absolutely unnecessary,” says Dr. Morris. “It is almost implausible that the benefits can outweigh the costs. Prosthetic joint infections are extremely uncommon while side effects and complications from antibiotics are rather common.”

So you would be well advised to follow the recommendation of your dentist and forgo the antibiotics. “The routine use of antibiotics for prevention [of infection] in healthy patients is not indicated by the evidence,” says Dr. Sutherland.

Paul Taylor, Sunnybrook’s Patient Navigation Advisor, provides advice and answers questions from patients and their families, relying heavily on medical and health experts. His blog Personal Health Navigator  is reprinted on Healthy Debate with the kind permission of Sunnybrook Health Sciences Centre. Email your questions to AskPaul@sunnybrook.ca and follow Paul on Twitter @epaultaylor

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