Tagged: AAP

“Flossing Has No Effects”

Update below.


No wonder when our professional societies and academies want to promote it with the above images. The Facebook page of the German Society of Periodontology features the left image while the right supports a recent statement by the American Academy of Periodontology’s President, Dr. Wayne Aldredge, regarding the U.S. Departments of Agriculture and Health and Human Services recent decision to remove flossing from the federal 2015-2020 Dietary Guidelines, citing the gap in quality research.

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How It All Began


Readers may have noticed my dismay about our “thought leaders'” recent attempts to revive the perio/systemic issue despite emerging evidence of no or very small, irrelevant, effects of periodontal treatment in large-scale intervention studies on  HbA1c in type 2 diabetes, or pregnancy outcomes.

I had yesterday discussed via email with a critical mind in the U.S. the results of another intervention study on cardiovascular events which never made it beyond a pilot study, the Periodontitis and Vascular Events, or PAVE, study. Since periodontitis patients were not randomized according to whether they received periodontal treatment but according to a community comparator (referral to community dentist with copy of x-rays and letter with diagnosis and recomendations for treatment), I had argued that such a design would not fulfil criteria of an RCT since patients who get proper periodontal treatment in the comparison group may fundamentally differ from those who won’t care. However, patients who won’t care in the test group would get the treatment anyway. So, interpretation of biased results would be difficult if impossible. Not surprising, the PAVE study did not get funding after the pilot phase (Beck et al. 2009) [pdf], which resulted in non-significant differences anyway, possibly (but not inevitably) due to lack of statistical power.

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Floss or Die

Systemic Health

New Orleans was still the Big Easy. Hurricane Katrina would devastate the southern metropolis about a decade later, and my attendance of the annual meeting of my main professional society was a nice relief of the daily monotony at my dental school at home. I met many of my colleagues and I had a fantastic dinner on a Mississippi paddle steamer which was sponsored by a company with which I was working at that time.

It was one of the very first occasions that scientists in my discipline talked about a possible relationship between poor oral health and dangerous chronic conditions such as cardiovascular and cerebrovascular diseases. One of our most distinguished Professors in the field commenced his presentation with the message “Floss or Die”, a really frivolous statement. He later put the alleged relative risk for getting an infarction or stroke to 1.3 or so in case of more severe oral disease. It was the beginning of an endless discussion which mostly interested the numerous practitioners who, whithout any knowledge about odds or risk ratios, bothered their patients during the next decade with the menace of myocardial infarction, ischemic stroke, low birth weight, etc., if their oral diseases had not properly been treated. Most of this has vanished in the meantime and more realistic views have emerged.

What I didn’t know at that time was that the distinguished Professor in Oral Biology had just received an award in Economics. Not the real Nobel Prize but the “IgNobel Prize”. It stands for ignoble, and it is in fact a parody for achievements that “first make people laugh, and then make them think.” The chief sponsor of the prize is the Annals of Improbable Research which is a successor to a periodical that satirized scientific publications. That particular year, Jacques Chirac was among the laureates who, as the French President, had just launched a series of atomic bomb tests in the Pacific Ocean while the world was observing the 50th anniversary of the Hiroshima massacre. It was the Peace prize, of course. Understandably, he didn’t show at the ceremony in Harvard University’s Memorial Hall where the prizes were conferred about 2 months before the real ones each year since 1991.

Our distinguished Professor got the prize in Economics for his remarkable discovery that “financial strain is a risk indicator for destructive periodontal disease.” Of course, he didn’t accept the prize either but rather ignored the event. It was long before the financial markets went out of control, somewhat before the dot-com bubble emerged and finally burst in 2000. People at risk for gum disease (according to our Professor those in financial trouble) have not participated in either bubble, I suppose.

All of this is certainly not related to the decline of periodontal disease which has been observed over the last decade or so. A slide with “Floss or Die” is still in use to attract the interest of my undergraduate and graduate students. But as ever, more as a joke than a serious suggestion.

First published at Freelance.

Strong Evidence For Minor Effects

The recent joint workshop of the European Federation of Periodontology and the American Academy of Periodontology, apparently meant to revive again (and once and forever establish) the periodontitis/systemic disease issue, has resulted in remarkably weak conclusions in some of the seminal papers, for instance,

  • As regards pregnancy outcome: “Current evidence from RCTs does not support the provision of periodontal therapy to improve pregnancy outcomes” (Michalowicz et al. 2013).
  • As regards diabetes mellitus: “The modest [a meta-analysis indicated a mean treatment effect of -0.36% HbA1c (CI -0.54, -0.19)] reduction in HbA1c observed as a result of periodontal therapy in subjects with type 2 diabetes is consistent with previous systematic reviews. Despite this finding, there is limited confidence in the conclusion due to a lack of multi-centre trials of sufficient sample size are lacking” (Engebretson and Kocher 2013).
  • As regards biomarkers and cardiovascular disease outcomes:  “There is […] limited evidence that these acute [short-term inflammatory response] and chronic changes [progressive and consistent reduction of systemic inflammation and improvement in endothelial function] will either increase or reduce CVD burden of individuals suffering from periodontitis in the long term” (D’Aiutu et al. 2013).

Very large intervention studies which could challenge existing evidence, as demanded during the workshop (“Well-designed intervention trials on the impact of periodontal treatment on prevention of ACVD [atherosclerotic cardiovascular disease] hard clinical outcomes are needed,” Tonetti and van Dyke (2013)), may be very difficult to conduct. Mainly beneficial effects of periodontal treatment (essentially unrelated to systemic diseases and conditions under scrutiny) have already been shown, so denial of treatment for control patients must be regarded unethical.

8 May 2013 @ 6:20 pm.

Last modified May 8, 2013.

Update on: Eventually Dead and Buried?

The recent joint enterprise by the American Academy of Periodontology and European Federation of Periodontology to address, once again, the meanwhile well-known connection between periodontal and systemic disease held at La Granja de San Ildefonso, Segovia in Spain in November last year has resulted in a number of review papers and consensus reports which have right now been published by the Journal of Clinical Periodontology and the Journal of Periodontology. Some are in fact informative and present lots of new information. In a press release (strangely called “manifesto”) on the occasion of the publication of supplements of the respective journals, and as regards epidemiological data on periodontitis and cardiovascular disease, it is stated that “[t]here is consistent epidemiological evidence that periodontitis imparts increased risk for future [sic!] cardiovascular disease, independently of other confounding factors.”

Well, while this statement seems to imply indeed a causal relationship (periodontitis increases the risk for future cardiovasuclar disease) the respective review article by Dietrich et al. (2013) explicitly studied (once again) the association between periodontitis and incident atherosclerotic cardiovascular disease (ACVD). However, association does not automatically mean causation, something which is nowadays fortunately known by most undergraduate medical and dental students.

In an attempt to focus on “the most robust studies” in terms of endpoint definition (incidence of ACVD) and exposure (clinically or radiographically assessed periodontal disease), the authors omitted, for example, the long considered large longitudinal studies based on early National Health and Nutrition Examination Surveys (NHANES) which had adopted now outdated measures of periodontal disease; but, apart from a number of  well-conducted prospective studies which might be able to give a certain hint about possible causation, included several case-control studies. This is absolutely okay when assessing “association” and not addressing “causation” [1].

Unsurprisingly, Dietrich et al. (2013) [2] arrived at similar conclusions (when it comes to the desired “association”) as the recent extensive systematic review by Lockhart et al. (2012) [3], of which I have written before, see here. Lockhart et al. (2012) fortunately warn, in addition, that “statements that imply a causative association between PD and specific ASVD [atherosclerotic vascular diseases]events or claim that therapeutic interventions may be useful on the basis of that assumption are unwarranted.” Dietrich et al. (2013) claim that the findings suggest that intervention studies would not be suitable in older subjects, say 60+ years, due to general weaker associations, which “present yet another formidable challenge for the design and conduct of future clinical trials that aim to address the question of benefits of periodontal therapy on adverse cardiovascular events.”

So, what’s the meaning of this new effort. No new attempt to prove a causal relationship has been or can be made at the moment. After 25 years, intervention studies which might reveal the more interesting aspect (causality) are still by and large missing. At least for the time being, one may trumpet once more that “[a] large body of research has indicated a relationship between periodontal disease and other systemic diseases” as Nancy L. Newhouse (the AAP’s new president) informed me before yesterday in an email. Well, how long have we been told this news now?

One comment on the sloppy presentation of the findings in the review paper by Dietrich et al. (2013). While the absolutely necessary information about the 12 selected studies (to get information about the prospective or case-control design, the duration, the size of the study, its outcome) is buried in the supplementary material, the main tables in the review itself are completely messed up. Important measures of associations can hardly be found. Figures were even manipulated (rounded), which was revealed only after checking the referred original paper [4].

I am afraid that the common cursory reader of either JCP or JP can only miss these data, does not understand and is not informed that inconsistent results in several studies and multiple testing may only weaken any desired conclusion in favor of a substantial association. In the worst case, he or she has to rely on the, well misleading EFP “manifesto” which seems to suggests indeed causality [5].


[1] Dietrich T, Sharma P, Walter C, Weston P, Beck J. The epidemiological evidence behind the association between periodontitis and incident atherosclerotic cardiovascular disease. J Clin Periodontol 2013; 40(Suppl 14): S70-S84: “Observational studies to date support an association between PD and ASVD independent of known confounder.” While the authors mention that “meta-analyses were not attempted due to heterogeneity of studies in terms of virtually all study characteristics”, which had been done in the past when looking at these huge prospective, long-term studies, but with rather sobering, weak associations between periodontal and cardiovascular disease, it is amazing that risk ratios, relative risks, hazard ratios and odds ratios in the presently selected studies, where subgroup analyses were a common feature, were low or at most pretty moderate, inconclusive and frequently even insignificant. So, whether a decade old studies with crude methodologies had been omitted or not did not really matter for the current conclusions.

[2] Dietrich et al. (2013): “Observational studies to date support an association between PD and ASVD independent of known confounders.”

[3] Lockhart PB, Bolger AF, Papapanou PN Osinbowale O, Trevisan M, Levison ME, Taubert KA, Newburger JW, Gornik HL, Gewitz MH, Wilson WR, Smith SC Jr, Baddour LM. Periodontal disease and atherosclerotic vascular disease: Does the evidence support an independent association?: a scientific statement from the American Heart Association. Circulation 2012;125:2520-2544, conclude [pdf] [T]he current evidence supports the notion that the incidence of ACVD, as represented by incident CHD, cerebrovascular disease and periopheral arterial disease is higher in subjects with PD or with better periodontal status, independent of many established cardiovascular risk factors.”

[4] For instance, a not significant hazard ratio in younger than 60-yr old subjects in the original paper by Dietrich, Jimenez, Krall Kaye et al. (Circulation 2008; 117: 1668-1674) of 1.55 for a bone score of 1 to less than 1.5 had been rounded up to 1.6 in the systematic review by Dietrich et al. (2013).

[5] When scrolling down, the first recommendation for practitioners is in fact misleading. The U.S. Preventive Services Task Force had already in 2009 recommended not to screen asymptomatic subjects with no history of coronary heart disease for non-traditional risk factors such as periodontitis to prevent respective events. Remaining recommendations sound, on the other hand, rather moderate, just reflecting that there is nothing new in the Perio-Cardio relationship:

  • “Practitioners should be aware of the emerging and strengthening evidence that periodontitis is a risk factor for developing [sic!] atherosclerotic cardiovascular disease, advising patients of the risk of periodontal inflammation to general as well as oral health.

  • Based on the weight of evidence, periodontitis patients with other risk factors for atherosclerotic cardiovascular disease, such as hypertension, overweight/obesity, smoking, etc. who have not seen a physician within the last year, should be referred for medical examination.

  • Modifiable lifestyle associated risk factors for periodontitis (and atherosclerotic cardiovascular disease) should be addressed in the dental surgery/office and within the context of comprehensive periodontal therapy, i.e. smoking cessation programs and advice on lifestyle modifications (diet and exercise). This may be better achieved in collaboration with appropriate specialists and may bring health gains beyond the oral cavity.

  • Treatment of periodontitis in patients with a history of cardiovascular events needs to follow American Heart Association (AHA) guidelines for elective procedures.”

5 May 2013 @ 12:55 pm.

Last update May 5, 2013.