In an announcement for his talk about periodontal treatment effects on type 2 diabetes at Europerio 8 in London later this year, exasperated Professor Thomas Kocher of Greifswald University in Germany promises to “dissect” the large multicenter trial by Engebretson et al. (2013) who could not find an effect on glycated hemoglobin in type 2 diabtes mellitus. The study had been published in late 2013 in JAMA, not in New England (Journal of Medicine). The large multicenter trial had long been attacked for not yielding the desired results (“a publication which we were really waiting for”).
Kocher was asked to talk in London about “why all the other small studies showed an effect” and he wants to find out “the issues why we [?] couldn’t see anything in the Engebretson study”. Well, it was actually Wenche Borgnakke who had got 20 other “reviewers” aboard who had already dissected the study by Engebretson et al. and has called for censorship.
As noted by Engebretson and Kocher 2013 in one of the numerous previous systematic reviews of RCTs on the effect of nonsurgical periodontal therapy and reported in Table 1 of their article, problems with the design of these small-scale, mainly single-center studies, which included some trials with adjunctive antibiotics, were plentiful. Problems with low and high baseline HbA1c levels and with questionable periodontal outcomes had been reported as well. Engebretson and Kocher (2013) report possible publication bias which means nothing else that studies without an effect on HbA1c might have gone unpublished. Based on this particular and numerous other systematic reviews, the evidence that nonsurgical periodontal therapy in fact has a relevant beneficial effect on HbA1c levels in type 2 diabetics may actually be regarded moderate. The study by Engebretson et al. adds heterogeneity to any meta-analysis which may downgrade this evidence to low. That is what our thought leaders alerts. That’s why censorship.
The large multi-center intervention trial by Engebretson et al. (2013), who had reported lack of any effect of non-surgical periodontal therapy on HbA1c levels in type 2 diabetes mellitus patients after 3 and 6 months, has been harshly criticized because of very moderate clinical improvements as regards pocket depth reduction (from mean 3.26 mm at baseline) of 0.4 mm (95% CI 0.4; 0.5 mm) and reduction of bleeding on probing (from mean 62%) of 19% (95% CI 15.7; 22.4). What was even more concerning was that, 6 months after seemingly intense treatment (at least 160 minutes of scaling and root planing followed by oral hygiene instruction and, for two weeks, twice daily mouthwash with 0.12% clorhexidine digluconate; then, at both 3- and 6-month follow-up examinations, further oral hygiene instructions and scaling/root planing for another hour), bleeding on probing was still seen at an average of 40% sites while, on average, 70% tooth surfaces were still covered by plaque (from 86% at baseline).
These are undeniable problems of the study. Claims that periodontal treatment was insufficient and, as a consequence, periodontal infection still present in most patients after periodontal therapy, may in fact be justified. It is the sheer size of the attack which is so appalling. Each and every editor of our professional journals and numerous further pundits, altogether 21, had joined, well, the public execution of the study’s principle investigator. Because of unwelcome results of a study with the potential of ending a story, or illusion, once and forever. And, absolutely inappropriate attempts of intimidation of scientists when writing,
“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 this 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.” (Emphasis added.)
So, censorship. This is absolutely unscientific. Meta-analyses are always preliminary and must incorporate new results on a continuous basis.