Contour-enhanced forest plot on the comparison of total ABO-OGS scores post-treatment between aligners and fixed appliances without the Li et al., 2015 study (2). ABO-OGS, American Board of Orthodontics Objective Grading System; AL, aligner; CI, confidence interval; FX, fixed appliance; M, mean; MD, mean difference; N, number of patients; SD, standard deviation. Contours correspond to different effect magnitude and the red dotted line corresponds to 95% random-effects prediction.