All interventional oral health CSR published between 2003-2021 were sourced. Study characteristics were extracted at the level of the CSR and the outcome/meta-analysis. One-hundred-five CSR were eligible and analysed.
Almost a third of CSR (n=67) were excluded as a GRADE rating was not available. The most prevalent type of primary studies included in the CSR were randomized studies (93.4%) and the most used measure of effect was the risk ratio (67.3%). Overall, the certainty of the evidence according to the GRADE rating for all examined outcomes was very low/low (88%). The two most common reasons for downgrading the confidence in the evidence were study limitations (Risk of bias) and imprecision. The odds of moderate/high vs. low/very low-GRADE rating are higher for the primary compared to the secondary outcomes after adjusting for year and number of trials (OR 2.49; 95% CI: 1.09, 5.65; P=0.02). Per year (2010-2021 period) the odds of moderate/high vs. low/very low-GRADE rating decrease (OR 0.73; 95% CI: 0.60, 0.90; P=0.01), and as the number of trials per comparison increase the odds of moderate/high vs. low/very low GRADE rating increase (OR 1.13; 95% CI: 1.01, 1.25; P=0.001).
The certainty of the evidence in oral health when assessed with the GRADE rating remains predominantly low or very low.