Objective To assess the evidence of Cochrane systematic reviews relating to oral hygiene care. Methods Issue 3, 2008 of The Cochrane Library was searched for systematic reviews relating to oral hygiene care. Results Four systematic reviews with the forty-five randomized controlled trials (RCTs) were included. The methods of forty-five studies were of lower quality with high risk of various biases. Conclusion There is insufficient evidence to support oral hygiene care. The overall quality of RCTs about oral hygiene care is generally low. Analysis of the included trials shows some trials have no clear description of randomization methods, allocation concealment, sample size calculation, and intention-to-treat analysis. To improve the quality of reporting of RCTs, Clinical Trial Registration and Revised consolidated standards of reporting trial (CONSORT) statement should be introduced as guidelines into the trial design.