Fig. 5

Meta-regression using interaction between region and class of medication (antibiotics/non-antibiotics) used for irrigation. The interaction explained almost all of the variance among enrolled studies. Meta-analysis was performed using restricted maximum likelihood estimation. Size of the box represented study weight. Symbols represents indicated RRs and 95% CIs of the study and dotted line indicated the American study. Orange symbols indicated study using non-antibiotics (povidone-iodine). Gray shading area represented 95% CIs of the regression line