It was tempting to write another post in the Periodontal Myths and Mystery Series – Clinical Measurements in Periodontal Disease. Guesswork whenever it comes to submarginal landmarks such as the cemento-enamel junction and bottom of the pocket; or, even worse, an assumed “tangent to the prominences of two roots” to “measure” furcation involvement. After having introduced and refined case definitions of mild, moderate and severe periodontitis for epidemiological surveys in the past decade, the same authors representing the American Academy of Periodontology and the U.S. Centers for Disease Control and Prevention had to concede, in a recent article in the Journal of Periodontology, that,
[t]hese subgroups [mild and moderate periodontitis] are not truly ordinal [sic] as the label suggests because many ‘moderate’ cases had insufficient pocket depth to qualify as ‘mild’ and we have therefore combined them and used the label ‘other‘ periodontitis,
adding even more confusion . When the paper went online earlier this year, I had contacted one of the authors, Dr. Wenche Borgnakke, to explain that sentence. I had even suggested,
So, in some cases there was >= 4mm CAL but no deep pockets of >=5mm, only 4mm. So, if CAL would have been 3mm, one would have assigned it to ‘mild’, but since it was 4+mm, it had been ‘moderate,’
asking her whether I was possibly right. Unfortunately, she did not respond.
It had long been claimed that Aggregatibacter actinomycetemcomitans is strongly associated with localized aggressive periodontitis. In particular, A. actinomycetemcomitans has even been involved in the pathogenesis of aggressive periodontitis. Later it had been realized that this bacterium occurs frequently also in other forms of periodontitis and even gingivitis. And, other bacteria, such as Porphyromonas gingivalis, may be involved in the pathogenesis of both localized and generalized aggressive periodontitis.
One of the upcoming issues of Periodontology 2000 is dedicated to all aspects of, what has turned out, very controversial aggressive periodontitis. Eija Könönen at Turku University and I had been asked to scrutinize the voluminous literature on the microbiology of aggressive periodontitis . The following is a brief summary of the role of A. actinomycetemcomitans as a causative agent and new findings of open-ended molecular techniques regarding the microbiome of localized and generalized aggressive periodontitis.
Criteria for Causality
Sir Bradford Hill had described about 50 years ago criteria for possible causal relationship of certain risk factors for complex chronic diseases (Hill 1965), see here [pdf]. These criteria ultimately proved that smoking causes some forms of lung cancer. Among them, strength of association (including consistency and specificity), temporality of events (the causal factor has to be present before the onset of the disease) and experimental evidence (intervention trials) are of great importance as is for instance the biological gradient (dose-response relationship), while plausibility, coherence with laboratory findings, and analogy are not, or not so much .
Recently, Howick et al. (2009) have re-arranged Hill’s criteria , see here [pdf], putting much emphasis on direct evidence for a causal relationship which comprises the size of the effect (after adjusting for possible confounding), the appropriate temporal and/or spatial proximity (the cause precedes the effect and the effect occurs after a plausible interval; the cause occurs at the same site as the intervention), and dose-responsiveness and reversibility. What they call mechanistic evidence (evidence for biological, chemical, or mechanical mechanisms of action; and parallel evidence (coherence, replicability, similarity) would therefore not suffice to prove causality.
Methods and Results (I)
A systematic literature search was done in PubMed using the following focused question:
“Do prospective studies exist which may indicate a causal relationship between Aggregatibacter actinomycetemcomitans and the development of periodontitis at young age?”
Search terms were: (“actinobacillus actinomycetemcomitans”[MeSH Terms] OR (“actinobacillus”[All Fields] AND “actinomycetemcomitans”[All Fields]) OR “actinobacillus actinomycetemcomitans”[All Fields] OR (“aggregatibacter”[All Fields] AND “actinomycetemcomitans”[All Fields]) OR “aggregatibacter actinomycetemcomitans”[All Fields]) AND (“aggressive periodontitis”[MeSH Terms] OR (“aggressive”[All Fields] AND “periodontitis”[All Fields]) OR “aggressive periodontitis”[All Fields]) AND (“longitudinal studies”[MeSH Terms] OR (“longitudinal”[All Fields] AND “studies”[All Fields]) OR “longitudinal studies”[All Fields] OR “prospective”[All Fields]), which yielded 63 papers published between 1986 and 2011. Continue reading