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Sir, Dr Ahearne raises an important point regarding the problem of evaluating contradictory literature1. Clinical trials are limited by both the nature and size of the study or sample

population. The most important evidence that the results of such studies provides can often only be applied to a more general population than the subjects in the study represent. Thus, the

conclusions from Moore _et al_2 can only be related to a population that has the same characteristics as those recruited: in this case, a South London group of subjects with a prevalence of

disease representative of most UK populations. As stated in the paper, these results are not consistent with those previously published regarding populations studied in the USA which were

drawn from groups with a much higher prevalence of severe disease. Differences in the study populations may also explain the conflicting results between Moore _et al_2 and Radnai _et al_3. A

second potential reason for differences arises from the numbers of subjects and type of study. In the studies referred to by Dr Ahearne, the contrast was between a large prospective study2

and a small case-control study described as a pilot study3. Evidence-based public health and clinical dentistry must be based on well-conducted research, but no single clinical trial can

produce conclusions related to all people in all places all of the time. This can only be approached through systematic review of a number of published clinical trials. Unfortunately, for

many clinical questions, no such conclusive evidence exists, and practitioners must weigh carefully the evidence that is available (be it research papers, reviews or clinical experience) and

judge its relevance to their own clinical situation. No one said evidence-based dentistry was easy! REFERENCES * Ahearne J . Evidence based dentistry _Br Dent J_ 2004; 197: 594. Article 

Google Scholar  * Moore S, Ide M, Coward PY, Randhawa M, Borkowska E, Baylis R, Wilson RF . A prospective study to investigate the relationship between periodontal disease and adverse

pregnancy outcome. _Br Dent J_ 2004; 197: 251–258. Article  Google Scholar  * Radnai M, Gorzo I, Nagy E, Urban E, Novak T, Pal A . A possible association between preterm birth and early

periodontitis. A pilot study. _J Clin Periodontol_ 2004 31: 736–741. Download references AUTHOR INFORMATION AUTHORS AND AFFILIATIONS * London S Farrell neé Moore, M Ide & R Wilson

Authors * S Farrell neé Moore View author publications You can also search for this author inPubMed Google Scholar * M Ide View author publications You can also search for this author

inPubMed Google Scholar * R Wilson View author publications You can also search for this author inPubMed Google Scholar RIGHTS AND PERMISSIONS Reprints and permissions ABOUT THIS ARTICLE

CITE THIS ARTICLE Farrell neé Moore, S., Ide, M. & Wilson, R. Contradictory literature. _Br Dent J_ 198, 487 (2005). https://doi.org/10.1038/sj.bdj.4812291 Download citation * Published:

23 April 2005 * Issue Date: 23 April 2005 * DOI: https://doi.org/10.1038/sj.bdj.4812291 SHARE THIS ARTICLE Anyone you share the following link with will be able to read this content: Get

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