Four-Rooted Maxillary First Molars: A Systematic Review and Meta-Analysis

Figure 5

Funnel Plot. The vertical red line marks the median of all studies (0.047). The two gray curves mark the 95% confidence interval, assuming a true percentage of 0.047. The left gray line marks the lower limit of the 95% CI and runs almost parallel to the y-axis; i.e., the lower boundary is 0. Overall, the percentage of teeth with 4 roots is small (0.047%); therefore, a large part of the studies shared 0%.