1. Customer Service Management Office, Shandong University Affiliated Jinan Central Hospital, Jinan, Shandong 250013, P.R. China
2. Department of Stomatology, Jinan Maternity and Child Health Care Hospital, Jinan, Shandong 250001, P.R. China
3. Department of Stomatology, Shandong University Affiliated Jinan Central Hospital, Jinan, Shandong 250013, P.R. China