Funding for this research was provided by:
National Natural Science Foundation of China (81171006, 81571002)
Beijing Municipal Natural Science Foundation (7162203)
Beijing Council of Science and Technology (Z121107001012024)
Text and Data Mining valid from 2018-03-21
Received: 4 August 2017
Accepted: 8 February 2018
First Online: 21 March 2018
Ethics approval and consent to participate
: This study was conducted under the ethical guidelines of the 1975 Declaration of Helsinki and was approved by the review committee of the Peking University School and Hospital of Stomatology.
: Not applicable.
: The authors declare that they have no competing interests.
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