That periodontitis and diabetes mellitus are related is known for more than 100 years. While Beck et al. (2019), in their contribution to the JDR Centennial Series on 100 Years of Progress in Periodontal Medicine, start out with a paper by Williams and Mahan (1960), which is mentioned as the first landmark paper (allegedly the first study showing that periodontal therapy reduces insulin requirement; but this study had only shown that removing all teeth with advanced decay improved glycemic control), the latter authors quote a booklet by Otto Georg Grunert of 1899 a patient guidebook for diabetics: Ueber Krankheitserscheinungen in der Mundhöhle beim Diabetes: Therapeutische Winke für Diabetiker. In particular the medical profession had known about the link of diabetes mellitus and oral disease for long.
Further landmark, or “milestone”, papers in Beck et al.’s list on the diabetes-periodontitis relationship appeared around 1996, when late Professor Robert J. Genco, for the first time, had used a slide with the message, Floss or Die! on the occasion of the annual meeting of the American Academy of Periodontology in New Orleans. Some of these studies indeed sparked the idea that it would be possible to reduce HbA1c, the marker of diabetic control, by proper periodontal treatment of diabetic patients.
There is still controversy about the meaningfulness of HbA1c reduction in diabetics upon non-surgical periodontal therapy. One may get the impression that the number of systematic reviews (SR) on the issue surpasses the number of quality randomized clinical trials (RCT). The most current update by the Cochrane Collaboration (Simpson et al. 2015) had concluded that,
There is low quality evidence that the treatment of periodontal disease by SRP [scaling and root planing] does improve glycaemic control in people with diabetes, with a me an percentage reduction in HbA1c of 0.29% at 3-4 months; however, there is insufficient evidence to demonstrate that this is maintained after 4 months.
I will stick to that statement although I am fully aware that attempts are being made by representatives of our profession of considering rather systematic reviews of SRs as if that would lead to other research outcomes. For still interested readers, I have reported and discussed the issue in numerous blog posts, see e.g. here, here and here.
Treating all kinds of systemic ailments by proper scaling and root planing has been an illusion of certain periodontists for some time. As a healthy antidot, one should carefully read an interview with Jan Lindhe, published some time ago, where he warned us:
I think that the dentist’s area is pretty well described – it’s intraoral and also maxillofacial in a sense but the dentist shouldn’t be a pseudo-doctor for all types of disorders. (Emphasis added.)
Claims and denials of clinically relevant effects of, in particular, non-surgical periodontal treatment on markers of diabetic control have not only led to a surge of new randomized clinical trials and systematic reviews thereof. If anybody had hope that the current frenzy has found a happy end with the updated and very comprehensive Cochrane review by Simpson et al. (2015) (s)he has been mistaken. In the June issue of the Australian Dental Journal, Botero et al. (2016) report on an umbrella review in which they systematically reviewed all systematic reviews on the subject, be it with or without meta-analysis, published between 1995 and 2015. The paper has been accepted for publication on January 20, 2016. It has to be emphasized that using the term “umbrella review” is somewhat misleading. In a strict sense, an umbrella review assembles together several systematic reviews on the same condition in the presence of many treatments or many important outcomes.
In a previous post, I have expressed considerable concern about an assumed advertorial in our leading periodontal journal, JCP. Quintessence Publishing was about to launch their fourth installment of “3D” animated, short (each 15-17 min) movies all called Cell-to-Cell Communication, “Oral Health and General Health – The Links between Periodontitis, Atherosclerosis, and Diabetes.” Previous movies have been offered for purchase by QuintPub for a remarkable amount of around $100. Luckily, the new one can now be found on the EFP homepage and accessed by members and non-members for free.
Currently, teachers experience a general problem, a surge of published systematic reviews where slightly modified search criteria have led to slightly different bunch of papers with slightly different results of meta-analyses. Systematic reviews have once been welcomed as valuable tool to either end a story once and forever (if evidence for or against a certain treatment or association was overwhelming), or call for more conclusive randomized controlled trials (RCT) after still open questions had been identified. If, after any new RCT, editors of our professional journals would accept considering a new systematic review for publication, which basically ruminates already published RCT summaries but adds just another study without changing main conclusions, it will in fact become difficult to keep pace with what some call “emerging evidence”.
One main reason why evidence based medicine has to be taught to undergraduate students is to provide future health care workers with proper tools and train specific skills to conduct brief systematic reviews of identified randomized controlled trials themselves. Here on this blog, I had posted a couple of quick examples, see here, here and here.
In particular the latter of the above examples has dealt with the question whether the large multi-center trial by Engebretson et al. (2013), which had reported no effects of periodontal therapy on HbA1c levels in diabetics, would nullify the conclusion (that nonsurgical periodontal treatment may reduce HbA1c levels by about 0.4%) of previous meta-analyses of smaller and mainly single-center RCTs with similar settings.
Engebretson et al. (2013) had listed possible shortcomings of their study. However, that oral hygiene of study participants had not improved was considered by most of our professional leaders scandalous. Further issues for unprecedented criticism included “nearly normal” HbA1c levels at the outset and extreme obesity of participants. Engebretson’s unwelcome results had been reviled by an armada of 21 editors of our key journals, presidents of our main scientific societies, and further periodontal experts. Criticism had culminated in a very strange recommendation.
“Given the inconlusive nature of these data, we recommend that the existing body of evidence in which meta-analyses consistently conclude that successful periodontal therapy appears to improve glycemic control, should instruct us until results from future studies are reported. We urge all interested parties to refrain from using these study results as a basis for future scientific texts, new research projects, guidelines, policies, and advice regarding the incorporation of necessary periodontal treatment in diabetes management.” (My emphasis.)
In other words, forget about Engebretson et al. and continue quoting more favorable results from existing meta-analyses of RCTs on the effect of periodontal therapy on diabetes control. A quick analysis revealed that it won’t nullify a mean HbA1c reduction in diabetics by nonsurgical periodontal therapy, but that considerable heterogeneity was introduced by including Engebretson’s study which may in fact lower the grade of evidence. I had entered meta-data of Engebretson and Kocher 2013 in an amazing tool for meta-analysis and had added findings by Engebretson et al. (2013). That might have been premature, see below.