Author contributions
Yong Zhou: conceived the ideas, analysed the data, wrote the main manuscript text; Fengying Sun : collected and analysed the data; Zhoujing Zhang and Xinxiu Duan: collected the histological data; Xianyan Long and Xiang Liu: collected the CBCT data; Duohong Zou and Jiacai He: conceived the ideas and edit the manuscript. All authors reviewed the manuscript.