Results
Eligible Cochrane Systematic Reviews
The search yielded 278 Cochrane systematic reviews that specifically addressed dentistry and oral health issues. After 7 duplicates were removed, we finally included 37 systematic reviews focused on paediatric oral health.
Characteristics of Included Cochrane Systematic Reviews
The median year of publication was 2008 (range 2002–2013) ( Table 1 ). Most systematic reviews (57%) were performed in the United Kingdom. The reviews mainly concerned interventions for the prevention of dental caries (n = 16), orthodontic treatment and oral surgery (n = 4 for each domain), treatment of dental caries (n = 3) and behavior management (n = 2). Details are given in Additional File 1: Table S1 .
Comparisons of Primary Outcomes
In 30 reviews, no meta-analysis was performed for primary outcomes in 65 comparisons: for 9 comparisons, no RCT existed for the primary outcomes; for 53 comparisons, only 1 RCT existed for the primary outcomes; and for 3 comparisons (2, 3, and 3 RCTs), no meta-analysis was performed for the primary outcomes. In 15 reviews, 65 meta-analyses were performed for primary outcomes (at least 2 RCTs included). Among the 65 meta-analyses, the median number of RCTs per meta-analysis was 3 [Q1–Q3 2–6, min–max 2–133] and the median number of patients per meta-analysis was 360 [Q1–Q3 182–1,673, min–max 50–65,179]. The number of meta-analyses with continuous outcomes was 61 (94%). Details are given in Additional File 2: Table S2 .
Methodological Quality of Cochrane Systematic Reviews
The overall quality of the selected reviews was high according to the AMSTAR checklist. In all reviews, the reporting of 8 of the 11 items was adequate (Figure 1). The weakest area was failure to report the likelihood of publication bias, in 14 reviews (38%), which did not assess publication bias. One review did not use "grey" literature as an inclusion criterion and in another, the methods used to combine the findings of studies were inappropriate.
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Figure 1.
Assessment of methodological quality of included studies using AMSTAR.
Implications for Practice in Cochrane Systematic Reviews
For the 37 systematic reviews, 7 (19%) concluded that specific interventions should be implemented in practice (ie, interventions for which research showed that benefits outweighed harms), and 1 concluded that specific interventions should not be used in practice because of ineffectiveness ( Table 2 ). All experimental interventions that had been shown to be effective involved prevention of dental caries. Research evidence supported the effectiveness of topical fluoride treatments (with toothpaste, gel or varnish) for permanent and deciduous teeth in children and adolescents, and sealants for occlusal tooth surfaces of permanent molars. We did not identify any intervention for which research showed that harms outweighed benefits. However, for 29 reviews (78%), the evidence was inconclusive because it was limited (see Additional File 3: Table S3 ).