Supplemental Table S1.

Sample Questionnaire

1. Please select your age group: A. ≤ 35 years B. 36-45 years C. 46-55 years D. ≥56 years

2. What's your type of practitioner? A. Endodontist B. General dentist

3. Years since conducting endodontic treatments independently: A. ≤ 5 years B. 6-10 years C. 11-20 years D. ≥ 21 years

4. What's your type of your healthcare facility? A. Public dental clinic B. Dental department of public hospital C. Private dental clinic D. Dental department of private hospital

5. The location of your healthcare facility A. Wuhan B. Other cities in Hubei

6. Has your endodontic practice recovered from COVID-19 disruption? A. Recovered totally B. Recovered partially C. Still suspended If your endodontic practice is still suspended, jump to question 18

7. How does the number of endodontic patients per month compare to that of this same period of time last year? A. Less B. More since resuming practice C. Almost the same

8. What kinds of COVID-19 tests have you completed for yourself to resume practice? (multiple answer question) A. RT-PCR for virus RNA B. ICG assay for IgM and IgG C. chest CT D. Other tests E. No test

9. Was your test result abnormal, including any positive result of RT-PCR, antibodies tests, abnormal chest CT scan imaging or any other abnormal result? A. Yes B. No C. No test

10. Did you inform patients of their COVID-19 infection risk, and required the signature of informed consent form from patients before endodontic treatment? A. Both B. Inform the risk to patients, but not required the signature of consent form C. Neither

11. What kinds of patient screening measures will you take before endodontic treatment at this stage? (multiple answer question) A. Green code∗ B. Body temperature test C. Questionnaire of epidemiological history D. Results of RT-PCR for virus RNA within last five days E. Results of ICG assay for IgM and IgG within last five days F. Results of chest CT within last five days G. Other measures H. No measure

12. What is the most common attitude of your patients towards paid screening measures? A. Feel it is necessary, affordable and cooperative B. Feel it is necessary, but complain about payment and does not cooperate very well C. Feel it is unnecessary, and uncooperative D. No paid screening measure taken

13. Except standard PPE of gloves, googles or face shield, mask and gown, what special measures did you use for routine endodontic treatment? (multiple answer question) A. N95 mask B. Protective suit C. Oral aerosol vacuum D. Powered air-purifying respirator E. Plexiglass aerosol shield for microscope F. Negative pressure operatory for treating COVID-19 positive or suspected patients G. Other measures H. Nothing special

14. Have you taken part in the work on front-line of COVID-19 of treating confirmed or suspected COVID-19 patients including designated hospitals, fever clinic, quarantine sites? A. Yes B. No

15. Have you received confirmed or suspected COVID-19 patients who have recovered after treatment, confirmed or suspected COVID-19 patients with no symptoms, or patients who have been in close contact to a COVID-19 patient, including referred and treated patients? A. Yes B. No

16. I am concerned for becoming infected with COVID-19 from endodontic practice. A. Agree/strongly agree B. Neither agree nor disagree C. Disagree/strongly disagree

17. What are the reasons behind your concern? (multiple answer question) A. Concerned for myself becoming infected with COVID-19 B.Concerned for my family becoming infected with COVID-19 C. Concerned for my patient becoming infected with COVID-19 during treatment D. Other reasons

18. The rubber dam plays an important role in preventing cross infection with severe acute respiratory syndrome including COVID-19. A. Agree/strongly agree B. Don't know C. Disagree/strongly disagree

^∗The “health code” service–run on the ubiquitous platforms Alipay and WeChat and developed for the Chinese government–give users color-coded designations based on their health status and travel history, and a QR code that can be scanned by authorities. People given a green code are allowed to travel relatively freely.