The number of references on systematic reviews in Medline continues to increase year on year. Figure 1 shows the results of using two different search strategies that we use for identifying potential articles for use in this journal. The first is a sensitive one designed for maximum identification of dental studies in Medline. The second a more specific one which is more focussed but may miss some dentally relevant studies. These have both been combined with a specific systematic review search strategy developed at McMaster Medical School (search strategies available on request from ebdeditor@nature.com). This shows that the number of dental systematic review references on Medline using the OVID platform (Ovid Technologies, New York, USA) have increased from 24 to 153 for the specific strategy and from 60 to 406 for the sensitive strategy between 1994 and 2005. I say references rather than reviews as not all of these references will be actual new reviews as some may be editorials, letters or how to conduct or assess reviews.

Figure. 1
figure 1

Number of Dental Systematic Reviews in Medline identified using two different search strategies

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The continued increased interest in systematic reviews in dentistry is good news, but there is still much work to be done regarding the quality of these reviews, as Glenny et al1 pointed out in their assessment of dental reviews in 2003. Of the reviews they included 97% searched Medline, 23% Embase and 10% the Cochrane Collaboration Trials Database (Cochrane Central), and while a range of other databases were used the authors felt that only 19% demonstrated that they had attempted to find all relevant studies. While restricted to Medline, figure 1 shows the potential impact in terms of the number of articles identified that the use of different search strategies can have on identifying relevant studies. The use of different databases can have similar effects.

The need to include other databases was discussed by Egger et al,2 and the recent Cochrane methodology review by Hopewell et al3 highlights the need to include grey literature in order to help minimise the effects of publication bias in reviews. Grey literature has been defined as literature that is produced at all levels of government, academia, business and industry in print and electronic formats, but which is not controlled by commercial publishers. The term grey literature has been accepted since the creation of the System for Information on Grey Literature in Europe (SIGLE) database in 1978, this database is now managed by the European Association for Grey Literature Exploitation (EAGLE).

So the title of the editorial is not merely a reflection of my greying hair and spreading waistline but a plea for future dental systematic reviews to take their lead from Cochrane and other medical specialities and make their literature searches wider in terms of the number of databases they search and include the available grey literature.