Category: Article Review

Periodontal Myths and Mysteries Series (IX) – Prediction Models (Part 2)

In my previous post, I have emphasized that relative risks for certain steps of a complex dental procedure should be multiplied, not added, to get an idea of the overall relative risk for a, say, catastrophic outcome like tooth loss. There is probably no evidence, however, for the figures of my hypothetical example taken from restorative dentistry research.

In contrast, plenty of evidence for various risk factors for tooth loss in periodontally diseased patients during maintenance therapy has been published in recent cohort studies. The information provided (called internal evidence) may in fact be used for validation in unrelated patient populations (external evidence).

Let’s consider a popular example. In the study by Fardal et al. (2004), in a private specialist practice, 100 consecutive patients with periodontitis had been recalled, after proper treatment, for maintenance visits for 9 to 11 years. A few teeth, i.e. 36 out of 2436 teeth present at baseline, were subsequently lost during supportive periodontal therapy (1.5% of all teeth), all due to recurrent periodontal disease. The authors conducted a logistic regression analysis with the patient as statistical unit and identified male gender, older than 60 years of age, and smoking as significant covariates with an unfavorable effect on tooth loss. Participating in the offered maintenance program was not significantly associated with tooth loss, as were other covariates. These results were reported in Table 5 of the paper (here slightly edited).

Schwendicke 2018c

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When the Professors Come – On Mortality, Re-birth and Sink Status

Sri Lanka

The Natural History of Periodontitis. Photo: C.R. Ramseier, under fair use

In 1970, four-hundred-and-eighty male employees of tea plantations in Sri Lanka had been examined for the first time by western periodontists in order to start a longitudinal study of the natural history of periodontitis. It was assumed that the cohort, who supposedly lived their entire life on the plantation, had been unaffected by any treatment of periodontitis and professionally recommended or supervised oral hygiene practices.

Several papers had been published already by the mid 1980s. The study went on, and after lots of turmoil and civil war in Sri Lanka, even the tsunami of 2004, an attempt was made in 2010 to contact all participants of 1970 (Ramseier et al. 2017). Seventy-five were still available.

Ramseier et al. (2017) emphasize, in the introduction to their paper that,

[h]ypothetically, studies following subjects over a number of decades may give better insight into undisturbed disease progression, particularly between subjects showing different disease susceptibility. In this context, the untreated Sri Lankan tea labourers  provided a unique opportunity to further study periodontal disease progression in humans unaffected by professional or individual oral care. (Emphasis added.)

Hypothetically. In reality, it’s unethical (see below). At least, after new insights into the disease progression had been gained in 1986, participants (human beings after all) should have been offered thorough information about causal agents (then, without doubt, well-known), preventive measures (well established) and, yes, proper treatment.

It is reported that the study by Ramseier et al. (2017) was approved by the local dental school (apparently none of its administration qualified as co-author) and the Institutional Review Board of the University of Hong Kong SAR [sic]. No governmental ethical committee was consulted. As regards the participants (who were between 55 and 70 years of age when re-examined; note that Sri Lankans had, in 2010, a mean life expectancy of 77.9 years at birth), they were, in 2010,

informed in their native language (Tamil) by a medical doctor about the details of the study. They then gave consent by finger printing due to illiteracy.

In 2010, authors report that, fortunately,

[a]ccording to the Medical officer and the administration of the Estates [Dunsinane, Harrow and Sheen in Pundaloya], the subjects’ diet improved over the period of 40 years, and the salaries of the subjects increased continuously. Yet, the older generation analysed in this study did not communicate with the outside world and the majority remained illiterate.

On the other hand, subject interviews confirmed

persistent lack of professional preventive oral health care or cleaning devices other than occasional use of bare fingers and ashes.

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Are Global Burden of Severe Periodontitis Estimates Reliable?

In a recent editorial in Quintessence’s Oral Health & Preventive Dentistry, Kocher & Holtfreter (2017) had asked, “Is the prevalence of periodontitis declining or not?” and had referred to the “landmark paper” by Kassebaum et al. (2014) in which the “global burden of severe periodontitis” was estimated at about 11%, or 743 million. The first Kassebaum paper had sparked considerable interest claiming that severe periodontitis was, in 2010, “the sixth most prevalent condition in the world.”

Kassebaum et al. 2014
Static prevalence and incidence rate estimates in 1990 and 2010 by Kassebaum et al. (2014)


As with all Global Burden of Disease (GBD) reports, in the paper by Kassebaum et al. (2014) data of a large number of very heterogenous epidemiological studies was used from all over the world and metaregression done. Published studies were supplemented with hand searches of reference lists of relevant publications and textbooks, government and international health organizations web pages, even conference reports, theses, government reports and unpublished survey data (gray literature).

Based on 65 prevalence studies, but only 2 (or 3; reported numbers differ in the flow chart describing selection of studies, and text) incidence studies as well as 5 (or 6) mortality (sic!) studies, Kassebaum et al. (2014) were able to estimate prevalence patterns in 1990 and 2010 (which strangely appear to be static) and made the strong claim (based on 2 or 3 studies) that incidence of severe periodontitis peaks at about age 38 years with more than 2000 new cases per year among 100,000.

Garbage in, garbage out?

A few words on heterogeneity of data. Kassebaum et al. (2014) had “identified 3 comparable quantitative indicators” of severe periodontitis, i.e. CPITN score of 4,  attachment loss of >6 mm, and pocket depth of >5 mm. Taken as a singular observation, none of these indicators, per se, would actually point to “severe periodontitis” which would be considered a much more serious disease. Extent of the disease is of importance when describing periodontal disease, something which periodontists are or should be aware of. Mixing partial and full-mouth probing in the various studies considered is another caveat (or flaw) in Kassebaum’s analysis. One might instantly think, garbage in – garbage out.

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New Updates On the Perio-Diabetes Link

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.

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Root-resective Therapy is a Predictable Treatment Option When Care is Administered at Each Phase of Therapy

The above is the conclusion of a recent retrospective evaluation of root-resected molars during a time-span of 30 years in a private practice. I would like to draw attention in particular to the last part of the sentence which is of utmost importance. I shall explain below what I think is necessary when reporting research findings in an honest way.

When has root resection been reported first?

Root resection, or amputation, is an old story. According to common wisdom, it had been Dr. John N. Farrar from Brooklyn, NY, who had reported first on so-called “radical and heroic treatment” of alveolar abscesses by amputation of roots of teeth [1], “in order to enable nature to have a better chance for cure.” Dr. Farrar correctly stated that, “if an entire tooth should be extracted from a diseased socket, the treatment might be termed highly radical.” He considered that such a treatment might not only unwise and unnecessary but “absolutely wrong and unscientific [sic].”

It is amazing that, some 130 years ago, reporting couple of cases was considered “science”. The times they are a changin’. Maybe in 100 years our current approach to what is still regarded scholarship and science will be ridiculed as well.

What can be achieved

Root resection or hemisection of furcation-involved molars are still common treatment options based on more rigorous research in the past 45 years. There may be also other indications, endodontic and iatrogenic. Implant dentistry is of course an interesting alternative, and a not so recent case series of patients attending a single private practice by  Fugazzotto (2001) from Milton, MA, had shown comparable results regarding successful treatment of either root resection of molars (n=701) or placing implants in molar locations (n=1472) after 15 and more years and 13 years, respectively. Indeed remarkable results, namely success rates of 96.8% for root resected molars and 97% for implants.

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