The effect of different types of water sources on dental unit waterline contamination: A systematic review and meta analysis.

To systematically review the effect of different types of water sources on dental unit waterline (DUWL) contamination. 5 databases were searched from their inception to December 23, 2023. Two reviewers independently extracted the data and assessed the quality of the literature. The risk ratio (RR) was used as measure of effect size in meta-analysis. The Grading of Recommendations, Assessment, Development and Evaluation (GRADE) was used for evaluating quality of the evidence. Meta-analysis was completed by RevMan 5.4.5 studies involving 561 water samples were quantified for meta-analysis. The results indicated that no significant differences were found in view of contamination rate (RR = 1.01; 95 % CI, 0.72-1.41;  = 0.96,  = 62 %; GRADE low)and detection rate of (RR = 0.78; 95 % CI, 0.15-4.13;  = 0.77;  = 83 %; GRADE very low) between using purified water and tap water as water sources of DUWL. The available evidence suggests that there is no significant difference between purified water and tap water in controlling DUWL contamination. However, the conclusions need to be further validated through more randomized controlled trials with robust design and a large sample size.