Text and Data Mining valid from 2019-08-13
Received: 16 May 2019
Accepted: 5 August 2019
First Online: 13 August 2019
Ethics approval and consent to participate
: The study not only received informed consent from all patients, but also received the support of the ethics committee of Henan Provincial Hospital of Stomatology, the First Affiliated Hospital of Zhengzhou University.
: Not applicable.
: The author declares that there is no competing interests.