Fang Y, et al. - In this review, the physicians assessed whether the apical diameter of teeth with necrotic pulp influenced the outcomes of regenerative endodontic treatment and determined the minimal apical size needed to obtain proper pulp revascularization. After regenerative endodontic treatment, the teeth with apical diameters <1.0 mm achieved clinical success. While, the teeth with apical diameters of 0.5–1.0 mm attained the highest clinical success rate, which could be related to other potential factors, including patient age, pulp necrosis etiology, preoperative apical radiolucency, procedure details, follow-up period, and sample size.