Erratum: Low‐intensity pulsed ultrasound promotes the formation of periodontal ligament stem cells sheets and ectopic periodontal tissue regeneration. Issue 5 (25th January 2022) - Li, Han; Zhou, Jie; Zhu, Mengyuan; Ying, Siqi; Li, Lingjie; Chen, Duanjing; Li, Jie; Song, Jinlin