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.
As regards “successful periodontal therapy” and the quality of the available evidence, consider the following example of the meta-analysis by Engebretson and Kocher (2013) which had been published a couple of months before the incrimiated large multicenter trial by Engebretson et al. (2013). Nine RCTs were identified where data of 398 test and 377 control patients could be extracted as regards possible effects of nonsurgical periodontal therapy on HbA1c levels in diabetics. The meta-analysis yielded an effect of -0.36% (95% CI -0.54; -0.19) on HbA1c. Comments by Engebretson and Kocher (2013) in Table 1 include that (1) Jones (2007) did not report (or observe?) a periodontal treatment effect. (2) In the paper by Yun et al. (2007) it was unclear whether subjects were on diabetes drugs. According to Engebretson and Kocher, the “[t]rial [was] not optimal for [the] research question because both groups received antibiotics.” Furthermore, no periodontal treatment effect was reported [or observed?]. (3) Chen (2012) did not observe an improvement of the metabolic status in either group although in both treatment groups [two different treatment regimes], periodontal conditions improved. (4) In the study by Kiran (2005) some subjects presented with HbA1c levels between 6 and 6.5% and should therefore be regarded well-controlled. (5) In the study by Katagiri (2009), HbA1c only decreased in a subgroup of patients where elevated levels of C-reactive protein decreased as well. (6) In two studies (Singh 2008, Sun 2011), changes in medication were not reported.
Any unbiased analyst of this systematic review must come to the conclusion that a meta-analysis must be regarded questionable due to the reported problems of most of the RCTs. The review had been produced on the occasion of a joint AAP/EFP workshop in November of 2012 with the clear intention of assessing any available evidence for the desired message for the public: Periodontitis is intimately connected with systemic health and disease.
But what about the harsh condemnation of our thought leaders as regards unacceptable clinical results after non-surgical periodontal therapy? The careful re-reading of some classic papers on scaling and root planing may be worthwhile. For example, in 1997 Haffajee et al. had published a paper which has been cited so far 396 times (Google Scholar). The study employed, for the first time, so-called checkerboard DNA-DNA hybridization in a clinical trial to characterize the flora of the 40 then known most prevalent bacteria at each tooth in 57 patients with chronic periodontitis. The above picture indicates that the prevalence of three bacteria, Porphyromonas gingivalis, Tannerella forsythia and Treponema denticola had significantly decreased after non-surgical periodontal therapy (scaling and root planing, or SRP) while one bacterium, now called Actinomyces oris, had increased in prevalence. The prevalence of most other bacteria did not change. Already in the abstract, authors mention that,
“Clinical improvement post-SRP was accompanied by a modest change in the subgingival microbiota, primarily a reduction in P. gingivalis, B. forsythus [now Tannerella forsythia] and T. denticola, suggesting potential targets for therapy and indicating that radical alterations in the subgingival microbiota may not be necessary or desirable in many patients.”
So, how impressive was “clinical improvement”? After all, scaling had been done quadrant-wise in weekly sessions and each session lasted for 45-60 minutes. Oral hygiene techniques were shown and proper home care reinforced at each treatment visit. Full-mouth maintenance scaling was done 3, 6, and 9 months after initial scaling. After 3 months sites with “gingival redness” had decreased from 68 to 57%, on average. Bleeding on probing was noticed at 58% sites before and 52% after SRP, on average. There was no significant change in the percentage of plaque-covered tooth surfaces, about 70% at either exam. Mean pocket depth decreased significantly from 3.3 to 3.1 mm three months after 3-4 hours of scaling and root planing, while the mean 0.11 mm attachment gain was not significant.
Any unbiased clinician must conclude that periodontal treatment was a grave failure. But this remained most probably almost unnoticed since the study’s “main results” fit so well with our expectations, i.e. the overwhelming importance of three possible pathogens P. gingivalis, T. forsythia, T. denticola; and the confirmation of the hypothesis of a “beneficial” organism, now called A. oris.
Meaning, results were not unwelcome, quite the opposite.
10 February 2015 @ 12:23 pm.
Last modified February 10, 2015.