Left brain and oral-systemic links

A few years ago, I had the pleasure of hearing Jeanne Robertson, a comedian from North Carolina.

Th Left Brain 01
Th Left Brain 01
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by Lynne H. Slim, RDH, BSDH, MSDH

A few years ago, I had the pleasure of hearing Jeanne Robertson, a comedian from North Carolina. Like me, she’s a Southerner who sometimes talks funny and says “y’all” instead of “yous guys.” The day I heard her speak, she was referring to her “left-brained” husband who obsessed over details, especially when given a shopping list. She referred to him as “over-degreed.” He once got into big trouble with a shopping list that was numbered from one to 10. Number five on the shopping list was a five-pound bag of sugar, so guess what he came home with? His bags were weighed down with five of those five-pound bags of sugar!

There is currently much discussion in the literature related to “emerging science” for an oral inflammation and distant site effect (e.g., oral-systemic link). Links between chronic periodontitis and systemic health problems such as diabetes, heart and lung disease, stroke, low birth weight babies, rheumatoid arthritis, and even pancreatic cancer have been proposed. Just as left- and right-brained folks are often polar opposites, there are oral health-care professionals who, for one reason or another, promote just about all of the oral-systemic links as they pop up in the literature. Some of these folks are right-brained, spatial intuitive types who would rather protect patients from potential associations of risks, and that’s not such a bad thing so long as the risks are reasonable, based on reliable science. On the other hand, there are individuals who “dig in their heels” before signing on. These individuals navigate through the complex, tangled web of research studies and wait patiently for strong evidence to confirm these links.

Last year, at the ADA 3rd International Conference on Evidence-Based Dentistry, I listened attentively to one of the featured speakers, specifically Philippe Hujoel. Dr. Hujoel has a curriculum vitae unlike any I’ve ever seen. He is credentialed as a dentist, periodontist, biostatistician, epidemiologist, and full professor at the University of Washington. I decided to interview Dr. Hujoel about the status of these links, and some of you will be challenged to revise your patient scripts, at least for the time being.

A headline in U.S. News and World Report (dated 1/29/09) stated that treating gum disease doesn’t decrease a pregnant woman’s risk of preterm birth or low birth weight (PTB/LBW) babies, and recently a study on periodontal treatment in pregnant women concluded that treatment does not reduce preterm birth or low birth weight. What research is this headline based on, and how is it different from past studies which showed an association between preterm birth risk and untreated periodontal disease?

The National Institute of Dental and Craniofacial Research funded two pivotal trials evaluating the impact of periodontal therapy during pregnancy on low birth weight.1 Both pivotal trials found that periodontal therapy does not lower the risk for low birth weight. These findings are consistent with our published systematic review of the evidence that periodontitis does not cause low birth weight.2 These findings are also consistent with our published evidence that periodontal therapy during pregnancy does not impact low birth weight. These pivotal trials confirm our expectations.

Some selected past studies may have created the impression of a causal association between periodontitis and low birth weight. In those studies, lifestyle factors were not taken adequately into account. One should not forget that in the early 1990s, smoking was still not recognized as a risk factor for periodontitis by the “experts.” It is informative to go back to the textbooks and expert reviews on periodontal disease written in the early 1990s and notice that lifestyle factors were not even on the radar screen as risk factors for periodontitis.

In my opinion, diet is another major lifestyle driver of dental disease epidemics, yet this factor also remains curiously forgotten in the current dental-systemic disease hype. Periodontal researchers who operate with the mindset of periodontal disease as an infection unrelated to lifestyle factors may be surprised when periodontal disease appears to correlate with systemic health. These researchers interpret correlation as causation, not realizing that smoking, diet, and other lifestyle factors are common causal factors for periodontitis and systemic outcomes such as low birth weight.

If a patient asks if treating periodontal disease will lower the risk of delivering a PTB/LBW baby, what’s the appropriate answer based on current reliable evidence?

There is no, and never has been, convincing evidence that periodontal disease causes low birth weight or that periodontal treatments will reduce adverse pregnancy outcomes. Expecting mothers can be informed that the same lifestyle factors that are hurting their teeth and gums are also hurting the fetus. Quitting smoking, avoiding sugars and high-glycemic foods (e.g., avoiding soft drinks), and reducing stress may benefit pregnancy outcomes, systemic health, teeth, and gums. Creating undue worry and stress in an expecting mother about how her bleeding gums or periodontal pockets will adversely impact the pregnancy is fear mongering. Dental advertising campaigns using fear mongering as a sales pitch may be appealing to the company sales representatives, but have no scientific evidence to support their claims.

Elective dental treatments should be postponed until after pregnancy. The safety of dental procedures during pregnancy remains largely unknown. Pregnancy is a dangerous time to experiment with unnatural exposures. Recommending a patient who just had scaling and root planing to take an over-the-counter anti-inflammatory drug could potentially increase the risk for certain birth defects, as anti-inflammatory drugs have been linked with hemifacial microsomia. Similarly, metronizadole — a periodontal antibiotic — can be associated with adverse pregnancy outcomes. Our work identified dental diagnostic radiation during pregnancy as another risk factor for low birth weight. The findings of our study have since been independently confirmed in a large cohort of British children.3 What other unknowns are out there?

For instance, to our knowledge, the safety of local dental anesthetics during pregnancy has not been evaluated by linking birth record data to receiving local anesthetic injections. It is better to be safe than sorry during pregnancy. And remember that these pivotal trials on the effect of periodontal treatment on birth weight do not provide evidence of safety. Those studies were designed to determine effectiveness, not safety. Their sample sizes were inadequate to even detect some of the common birth anomalies. The effect of treatments on birth anomalies and other outcomes require a very different approach than randomized controlled trials.

What do we know about the relationship between periodontal disease and cardiovascular disease?

It is the same story as for periodontal disease and low birth weight. We know that the lifestyle factors that put you at risk for coronary heart disease also put you at risk for periodontal disease and dental caries.

When asked by a patient about the link between periodontal and cardiovascular disease, what’s the right thing to say?

Empower the patient with healthy lifestyle choices that improve dental and general health. We should not underestimate the impact the dental profession can have on the general health of a patient. Smoking cessation advice in a dental office does have an impact. It increases by more than 40% the success rate in smoking cessation at one year. Just think about all the lives we can save this way. Our impact does not have to stop at smoking cessation advice. We can advise the patient on the adverse impact of high-glycemic foods on caries, gingival bleeding, and general health. Avoiding that sugary snack may not only cut the risk of losing teeth, but also a heart attack. To tell patients to “floss or die” is not evidence-based clinical advice, and ultimately may cause more harm than good if the patient remains uniformed about the well-established causal drivers of coronary heart disease and dental disease.

What’s an objective, nonbiased source of information for hygienists on the oral-systemic links?

Until astronomers or physicists can start providing medical or dental advice, there may be no such thing as objective, nonbiased information. There is a large body of evidence in the medical literature on the corrupting influence of money on information. Dentistry may not be immune to these problems. Be skeptical. Read the fine print. Do not believe that there is such a thing as unbiased information. Be particularly distrustful of pseudo-news events. An evidence-based approach puts a lot of emphasis on considering the impact of financial conflicts of interest. A first question one could ask when presented with evidence on oral-systemic links is: “Who benefits from presenting this information to me?” A second question could be: “Are those individuals or organizations presenting this information likely to tell only one side of the story, or worse, to suppress negative information?” If the answer to both questions is positive, it may be best to shred the information.

Besides some of the proposed periodontal-systemic disease associations, are there any dental-systemic disease associations that you are particularly interested in?

Dental-systemic disease associations are fascinating as they can provide clues to the etiology of diseases. Nobody has ever argued that dental and systemic disease are associated. This has been known for a long time. It is how these associations are interpreted that is key. We reported, for instance, that patients with periodontal disease are less likely to develop Parkinson’s disease.4 This does not suggest that people with Parkinson’s should have their teeth ligated and loaded with mega-doses of bugs. Rather, it provides indirect confirmation of the evidence that smoking, which is a factor in causing periodontal disease, may protect against Parkinson’s disease. Another investigator team indicated that tooth loss is associated with Alzheimer’s disease. This does not suggest that extracting teeth causes Alzheimer’s disease. Rather, it suggests that there may be a common causal factor out there — with a hint that this factor is high-glycemic dietary carbohydrates — that causes dental caries, periodontal disease, tooth loss, and Alzheimer’s disease. Possibly, the high-glycemic diets that cause dental caries may also lead to the accumulation of advanced glycation end products which are responsible for a wide variety of other chronic noncommunicable diseases.

Dental health may truly predict systemic health outcomes, because the lifestyle that is bad for teeth is ultimately bad for general health. Dentists and hygienists should consider this the next time a little kid with cavities sits in their dental chair. This little kid may very well become the obese adult with diabetes. And our dental professional advice on diet and lifestyle factors may reduce the chance of such long-term adverse health effects. So the real answer to your question is that focusing on the true drivers of dental-systemic disease associations may help reduce morbidity and mortality.


  1. Michalowicz BS, Hodges JS, DiAngelis AJ, et al. Treatment of periodontal disease and the risk of preterm birth. N Engl J Med. Nov. 2, 2006; 355(18):1885-1894.
  2. Hujoel P. Converting science into art: the challenge of the translationists. J Evid Based Dent Pract. Sept. 2008; 8(3):176-180.
  3. Daniels JL, Rowland AS, Longnecker MP, Crawford P, Golding J. Maternal dental history, child’s birth outcome and early cognitive development. Paediatr Perinat Epidemiol. Sepr. 2007; 21(5):448-457.
  4. Hujoel PP, Drangsholt M, Spiekerman C, DeRouen TA. Periodontitis-systemic disease associations in the presence of smoking — causal or coincidental? Periodontol 2000. 2002; 30:51-60.

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