The issue mentioned in the title was dealt with in a systematic review of the Cochrane Collaboration which was published 3 1/2 years ago. It confirmed that, since the publication of the PAVE pilot study in 2009, no further evidence had emerged. The authors of the Cochrane review concluded,
We found very low quality evidence that was insufficient to support or refute whether periodontal therapy can prevent the recurrence of CVD in the long term in patients with chronic periodontitis. No evidence on primary prevention was found.
Possible systemic effects of periodontal treatment had been claimed for a very long time, and lack of evidence, or evidence for their clinical irrelevance, had never been accepted by many colleagues, indeed.
The most recent attempt of reviving the largely lapsed interest by most of our medical colleagues in the Perio-Systemic link, in particular its cardiovascular branch, was launched earlier this week when a of the European Federation of Periodontology (EFP) met colleagues of the World Heart Federation (WHF) in Madrid. The aim of the workshop was to “explore the links between periodontal disease and cardiovascular disease and draw up a series of recommendations.”
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.)
Earlier this year, delegates of the European Federation of Periodontology (EFP) and the International Diabetes Federation (IDF) had met in Madrid for a joint workshop on an update of the Perio-Diabetes link. I had reported on the event and some key findings, quickly posted on the EFP web page, here.
Already on and after 24 August 2017, a Consensus Report by the two organizations was prematurely published, and quickly (temporarily) withdrawn, in the EFP’s Journal of Clinical Periodontology and the IDF’s Diabetes Research and Clinical Practice. I had managed to get a print-out of the not-yet edited (and later withdrawn) draft version published on the JCP Accepted Articles page and had noticed that most of the evidence presented was derived of yet-to-be published review articles based on the workshop proceedings.
The final version of the Consensus Report (Sanz et al. 2017, Early View Articles), including guidelines for patients and health professionals dealing with patients suffering from diabetes and periodontal disease, went online this week, but still references to review papers presented on the occasion of the workshop have a 2017 assignment and are not paginated which may make it more difficult for scientists and clinicians outside periodontology or dentistry to locate the final papers.
To be clear, when it comes to keeping our medical collegues, and in particular diabetologists, interested in the very long-known link between periodontitis and metabolic diseases, proving beneficial effects of periodontal treatment on diabetic control is crucial. All was fine as long as numerous published, small-scale, mostly single-center, and often poorly executed, trials apparently showed that thorough subgingival scaling in patients with both periodontitis and diabetes led to an about 0.4% reduction of glycated hemoglobin (HbA1c), at least after three or four months. As that would in effect spare an additional antidiabetic drug, diabetologists stayed interested. Although results in a few trials indicated that the effect was not long-lasting, i.e., no longer discernable after, say, six months.
In a recent commentary in the Journal of Periodontology, Merchant and Josey (2016) had suggested directed acyclic graphs to better comprehend the partly conflicting results from randomized controlled trials (RCT) on diabetic control after periodontal treatment in diabetic patients. In particular the influence of obesity caught their attention.
As a matter of fact, a remarkable number of systematic reviews (whose varying quality have recently been reviewed in at least two further SRs of SRs) have shown that numerous small-scale, single-center, often poorly designed RCTs had shown that the marker for diabetic control, HbA1c, might be reduced by, say 0.4% 3 months after in essence non-surgical periodontal therapy. The only large-scale, multi-center trial (DPTT) by Engebretson et al. (2013) couldn’t confirm that, though, which sparked harsh criticism of a large number of our thought leaders. A professor in the Department of Epidemiology and Biostatistics at the University of South Carolina, Columbia, Dr. Anwar Merchant himself had written a letter to the editors of JAMA pointing first to the fact that most participants in the paper by Engebretson et al. were utterly obese. He had further noticed that, “[i]n RCTs conducted among mostly nonobese individuals, periodontal treatment has been shown to reduce systemic inflammation2,4 and improve glycemic control among those with type 2 diabetes.2 However, periodontal treatment has not been shown to affect glycemic control in RCTs conducted among predominantly obese individuals with type 2 diabetes.1,3”
Obesity is positively correlated with inflammatory markers in the blood and strongly related to insulin resistance and metabolic dysregulation mediated by chronic systemic inflammation.5 These findings, taken together with results from RCTs evaluating the effects of periodontal treatment, suggest that the lack of effect of periodontal treatment on glycemic control observed in the study by Engebretson et al may be attributed to the high level of obesity in the study population. Therefore, the findings may be generalizable only to predominantly obese populations with type 2 diabetes.
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.