Characteristics of the Cochrane Oral Health Group systematic reviews

The Cochrane Oral Health Group (COHG) was formed in 1994 with the aim of producing systematic reviews that primarily include oral health randomized controlled trials (RCTs). The purpose of this cross-sectional study was to characterize reviews published by the COHG. In September 2013, the COHG database was accessed, and all publications were downloaded. Reviews with no studies identified according to the inclusion criteria were labeled "empty reviews." The complete Cochrane database included a total of 5,697 reviews, of which the COHG database included 142 reviews. Of these 142, 69 (48.6%) did not reach a conclusion, including 20 (14.1%) that were identified as empty reviews. Of the 122 non-empty reviews, 116 (95.1%) were based exclusively on RCTs. The median number of RCTs and patients included in the non-empty reviews were seven and 489, respectively. The median number of included RCTs and patients for reviews that reached conclusions were 12 and 934, respectively, and there were five RCTs and 211 patients for reviews without conclusions. Overall, the characteristics of the Cochrane oral health reviews (OH-CSRs) were similar to Cochrane reviews published in other disciplines (All-CSRs). The authors observed a significant difference in the median number of RCTs and patients included when reviews that reached conclusions were separated from those that did not. A greater proportion of empty reviews were present in OH-CSRs compared with All-CSRs. Turning the Cochrane reviews into a tool that is more relevant in clinical practice will require implementation of a methodology allowing inclusion of non-RCTs while controlling for possible bias.