Blood_bacteria
Did you know that getting your teeth cleaned can kill you?

Ok, that’s really not true (except in extremely rare, freak circumstances), but since today’s post is somewhat boring and unimaginative, I had to draw you in with what real journalists call a “hook”, and what hack writers like me call “click bait.” Looks like it worked.

Most of the time, a dental cleaning is a routine semi-annual event where you get to lie back, relax, and be made to feel guilty for not flossing often or well enough (even though we know it probably wouldn’t help a lot, anyway). The dentist or dental hygienist then scales the hard calculus deposits off of your teeth and polishes away the soft bacterial biofilm (formerly known as plaque), leaving your teeth feeling fresh and sparkly.

But did you know that even if your mouth is extremely healthy (i.e. your gums don’t bleed and you don’t have periodontal disease or cavities), even the most gentle dental cleaning forces untold multitudes of bacteria into your bloodstream, where they circulate throughout your body? Before you swear off dental cleanings forever though, keep in mind that this is almost always harmless; your immune system easily dispatches these invaders and you are none the worse for wear. However, for a small percentage of the population, these bacteremias (bacteria in the bloodstream) can be harmful and even deadly. Fortunately, we dentists have known about this connection for at least 80 years and have taken steps to reduce the risks of a lethal infection to almost zero. We do this by prescribing a dose of antibiotics prior to almost any appointment for those patients who are in a higher risk category of having a complication following a dental procedure. Having a dose of prophylactic antibiotics on board waiting for the bacteria to arrive helps to ensure that no infection will result.

As simple as that protocol might sound, it is much more complex and nuanced than that. In this blog post I want to unpack the concept of prophylactic antibiotic coverage for dental procedures: the pathophysiology of bacteremias, history of prophylactic antibiotic therapy, indications and contraindications, current guidelines, and the challenges we face trying to adhere to those guidelines.

The issue in a nutshell

As stated above, bacteria find their way into our bloodstream all the time, yet problems rarely occur. So you are probably asking: “why do we suddenly have to worry about it when we go to the dentist?” Excellent question, because as you know, we dentists are already trying to kill you with fluoride, mercury, and root canals. So it’s only logical that we would try to infect you by shoving germs through your gum pockets. It’s what we do.

There are two broad categories of patients who are perceived to be at a higher risk for an adverse outcome following a transient bacteremia: those with certain heart conditions or defects (particularly the heart valves) and those with artificial joints (knee or hip replacements, etc). Additionally, there may be situations in which antibiotic prophylaxis would be considered; for example poorly controlled insulin-dependent diabetics when surgery is performed, people living with HIV with very low CD4 counts, individuals with severe myelodepression (usually due to chemotherapy), or recent transplant recipients, including large organ or bone marrow transplants, to cite a few possibilities. In these unique (and fortunately rare) cases, the dentist, working in conjunction with the patient’s physician(s), will determine whether pre-medicating with antibiotics prior to a dental procedure is warranted.

Infective endocarditis (IE) is an infection of the lining of the heart chambers or valves with bacteria, fungi, or other organisms. IE occurs most commonly in people who have abnormal heart valves or had previous heart surgery. On rare occasions, it can occur in otherwise healthy people who have do not have a history of heart disease.

Here’s how a hypothetical case of infective endocarditis could occur following a routine dental procedure (in this case, the extraction of a tooth) in a patient with a defective mitral valve:

  • During an extraction there is a communication between the mouth and bloodstream. Bacteria (as well as other types of micro-organisms) enter the patient’s bloodstream. There are hundreds of species of bacteria, viruses, and fungi in the mouth, living in a delicate ecological balance. Most are harmless (or even beneficial), while others are responsible for causing such diseases as tooth decay, gum disease, strep throat, and a host of others. Mouths are messy.
  • These wayward bacteria then circulate in the bloodstream and adhere to the lining or valves of the heart, usually at a site of previous injury or surface irregularity or abnormality. In this example it’s around a leaky mitral valve (the valve through which blood flows from the left atrium into the left ventricle) where the flow is disrupted, creating eddy currents. Instead of being swept “downstream” like leaves in a fast-flowing stream, the eddies provide an opportunity for the bacteria to accumulate at or around the site of the defect.
  • The bacteria then grow on the valve surface, forming a small mass (called a vegetation) on the heart valves or lining. The valve or surface that is infected may then become secondarily damaged, causing Bad Things to happen.
  • A similar sequence of events occurs on patients who have a recently placed artificial joint – a hip or a knee, for example. Just like in the above example, instead of lodging in the heart, the bacteria are transported through the bloodstream to the site of the prosthetic joint, where they set up shop, leading to infection and the possible subsequent failure of the surgery.

A brief history and where we are today

In the pre-antibiotic era, dental infections could (and often did) kill people. In fact, in the 18th and 19th centuries, dental complications were the 5th or 6th leading cause of death, according to records from the time. For almost 100 years, the connection between heart valve defects and elevated cardiac risks from dental procedures has been known. In the 1930s, researchers first detected bacteremias caused by Streptococcus species following dental extractions, thus confirming the pathophysiology of IE. Early attempts to prophylactically manage these potential complications involved the use of sulfonamide antibiotics, anti-bacterial rinses prior to dental procedures, scaling and polishing teeth to reduce the bacterial load prior to extraction, irrigation of the extraction socket and cauterization of the gum tissue following an extraction, and many others. In one protocol suggested in the early 1940s, it was recommended that an autogenous streptococcal vaccine be obtained from a culture of the apical (i.e. root) area of the first tooth extracted, which was then to be administered before extraction of the following tooth. When penicillin became available following World War II, it became the antibiotic of choice for IE prophylaxis.

In 1955, the Committee on Prevention of Rheumatic Fever and IE of the American Heart Association (AHA) developed the first prophylactic protocol for use in patients with IE undergoing dental procedures. This protocol was recommended in patients with congenital or rheumatic heart disease who were undergoing dental extractions or other manipulations that affected the gingival tissues. The AHA panel stated that the aim of prophylaxis was to make high concentrations of the antibiotic available at the time of the manipulation and to maintain the presence of the drug in the bloodstream for several days in order to eliminate any bacteria that had adhered to the heart valves during the bacteremic episode. The recommended regimen was an intramuscular injection of a dose of 600,000 IU of aqueous penicillin and 600,000 IU of procaine penicillin dissolved in oil with 2% aluminum monostearate administered 30 minutes before the dental procedure. Alternatively (although less desirable), they proposed the oral administration of 250,000-500,000 IU (which is about 250ish milligrams) of penicillin 30 minutes before each meal and before bedtime, starting 24 hours before the dental treatment and continuing for 5 days afterwards, and with an extra dose of 250,000 IU of penicillin immediately prior to the procedure.

Since 1955, the recommendations for antibiotic prophylaxis for IE (also referred to as Subacute Bacterial Endocarditis (SBE) prophylaxis) have been revised nine times, the latest occurring in 2007. A general trend in the revisions has been twofold – a lessoning of the dosage of the antibiotic taken and eliminating conditions that require antibiotic premedication. Although the complications from a dentally-caused bacteremia can be severe, the evidence for the benefit of antibiotic prophylaxis is not all that robust. In fact, when the recommendations were last changed, Dr. Walter R. Wilson (the head of the committee which wrote the guidelines) stated:

We’ve concluded that if giving prophylactic antibiotics prior to a dental procedure works at all — and there’s no evidence that it does work — we should reserve that preventive treatment only for those people who would have the worst outcomes if they get infective endocarditis. This changes the whole philosophy of how we have constructed these recommendations for the last 50 years.

This, in my opinion, was a wise tack to take. If the evidence for benefit is scant, then why do it? On one hand, what’s the harm of one small dose of an antibiotic? That surely can’t do any harm, can it? Well, for the most part, no. One dose will not cause a “superbug” to evolve, nor will it significantly alter the microflora of the individual. That being said, a real concern is that, although rare, negative side effects can occur. A potentially fatal anaphylactic reaction to amoxicillin is possible, and has occurred on many occasions, so we cannot ignore the debit side of the risk to benefit ratio ledger. Other negative side effects (nausea, vomiting, interacting with other medications, etc.) can occur as well.

The current guidelines for dentists are as follows: for any patient, whether they have a cardiac defect or a recent joint replacement, a single oral dose of 2,000 milligrams of amoxicillin, one hour to their appointment, is prescribed. For those patients allergic to amoxicillin, clindamycin is usually prescribed instead.

So what’s the problem?

For the most part, there is no problem. Our patients who need premedication – for whatever reason – before they have a cleaning or a root canal or (heaven forbid!) an extraction, they take it, have the procedure, and return home uneventfully. In 31 years of practice, I haven’t killed anyone yet.

However, as a general dental practitioner, I am faced with a minor ethical dilemma on an almost daily basis, but to be fair I have to say that it’s almost always with the orthopedic physicians, not the cardiologists. I don’t want to throw my orthopedic pals under the bus, but I will say that, in my experience (cue worst phrase ever), they are the most difficult doctors to deal with regarding antibiotic prophylaxis. Here’s why: after a thorough review of the literature, the American Dental Association (ADA) determined that:

…[A] 2014 systematic review states, “In general, for patients with prosthetic joint implants, prophylactic antibiotics are not recommended prior to dental procedures to prevent prosthetic joint infection.”

In other words, there’s really not a problem with undergoing a dental procedure following joint replacement surgery (assuming no confounding factors such as uncontrolled diabetes or other immune compromises). Yet, most of the otherwise excellent orthopedic physicians I work with insist upon pre-medicating our mutual patients following joint replacement surgery – typically for two years, but often for life even though this protocol is not supported in the literature. I’m sure they just want to play it safe, or perhaps they continue recommending premedication because that’s what they’ve always done and old habits are hard to break.

Usually I comply with their edict, because it’s outside my legal scope of practice to call the shots for any medical procedure or condition. But if I am the one who prescribes the antibiotic at the behest of my patient’s physician (even if I know if it is contrary to current scientific evidence), what happens if the patient has an adverse reaction to the drug? Who is responsible? Me? The orthopedic doctor?

The problem is that bacteremias are caused every time you brush, every time you eat, and every other time you’re just sitting there. It’s not just confined to dental procedures. So why is the risk elevated only when you’re in my office? In an article published in the July 2016 issue of The Journal of Bone and Joint Infection, the authors state:

Transient bacteraemia occurs during daily oral hygiene activity (e.g., tooth brushing) and thus the cumulative risk for a haematogenous PJI (prosthetic joint infection) from tooth brushing is higher than that from a dental procedure. PJI after a dental procedure are rarely reported. On the basis of an epidemiological model, several thousand patients with artificial joints must receive antimicrobial prophylaxis to prevent a single PJI. Considering this ratio, the number of adverse events due to the antimicrobial compound exceeds the benefit of administering it by a large magnitude. Therefore, as a rule for the vast majority of cases, antimicrobial prophylaxis during dental procedures is not recommended. It is important that a patient has a good oral health status before joint implantation and that good oral hygiene is continuously maintained in patients with artificial joints.

In other words, prophylactic antibiotic therapy for patients with joint replacements is not indicated without extenuating circumstances. The risk of an adverse reaction to the antibiotic (statistically) far exceeds the risk of joint infection.

So, I suppose the purpose of this blog post is to inform our dear readers about the science of antibiotic prophylaxis prior to dental treatment; plus I want to issue a wake-up call to my physician colleagues to work with their dental allies to together determine what is best for their mutual patients and to follow the latest science based guidelines.

If you are a patient with a heart defect, please do your due diligence and consult with your cardiologist and dentist regarding the necessity of antibiotic prophylaxis. If you have had a joint replacement, also please do your due diligence and consult with your orthopedist and dentist regarding the appropriateness of taking an antibiotic prior to routine dental procedures. Ask for evidence and the most current guidelines regarding the best practice. Your health could be at stake.

Posted by Grant Ritchey

A Science-Based Dentist. Co-host of the Prism Podcast with Clay Jones, where we analyze the spectrum of scientific, rational, and critical thought.