Knowledge of Iranian Dentists, Dental Specialists, and Dental Students Towards COVID-19: A Preliminary Survey of 778 Subjects


avatar Farzin Sarkarat 1 , avatar Alireza Tootoonchian 2 , 3 , * , avatar Marjan Hosseinpour 2 , avatar Mehrzad Moghadasi 2 , avatar Vahid Rakhshan 4

Head, Oral and Maxillofacial Surgery Department; Head, Craniomaxillofacial Research Center, Dental Branch, Tehran Islamic Azad University of Medical Sciences, Tehran, Iran
Oral and Maxillofacial Surgery Department, Craniomaxillofacial Research Center, Dental Branch, Tehran Islamic Azad University of Medical Sciences, Tehran, Iran
Oral and Maxillofacial Ward, Buali Hospital, Tehran, Iran
Department of Dental Anatomy, Craniomaxillofacial Research Center, Dental Branch, Tehran Islamic Azad University of Medical Sciences, Tehran, Iran

how to cite: Sarkarat F, Tootoonchian A, Hosseinpour M , Moghadasi M , Rakhshan V. Knowledge of Iranian Dentists, Dental Specialists, and Dental Students Towards COVID-19: A Preliminary Survey of 778 Subjects. Shiraz E-Med J. 2020;21(12):e106515.



COVID-19 is a serious pandemic. However, no studies worldwide have assessed the knowledge of any healthcare workers, including dentists, towards COVID-19.


Given the importance of Iran as an epicenter of this disease, this preliminary study assessed the knowledge of dentists, dental students, and dental specialists towards COVID-19.


In this cross-sectional study, a questionnaire with 23 questions (three regarding sources of information and 20 regarding knowledge) was developed through a pilot study. It was distributed electronically to dental professions/students, 778 of whom completed it. Factors associated with knowledge were assessed using the chi-square test in SPSS (α = 0.05).


Above 70% of the responders answered correctly to all questions, except for six more technical questions, including handwashing-related questions. Age, specialization, and attendance at lectures and meetings did not play a role in grasping accurate information (all P values > 0.1). Men had poorer information (P = 0.014), and the sources of information were mostly official websites and social networks (P = 0.000).


Knowledge of dentists, dental students, and specialists towards SARS-CoV-2 is generally good, except in the case of more technical questions that need more education (especially regarding handwashing).

1. Background

The outbreak of the new coronavirus called SARS-CoV-2 has become a global health issue. Pneumonia caused by this virus (coronavirus diseases 2019, COVID-19) has become a pandemic and has involved most countries in the world (1). The virus has infected many people around the world, many of whom have died of infection. Because of the global outbreak of COVID-19, the World Health Organization (WHO) announced it as a pandemic and an emergency in the world.

A very high rate of virus transmission and spread and its considerable rate of fatality call for improving measures of COVID-19 prevention. An important component of such preventive measures is knowledge of people, especially health care professionals who play a major role in spreading the disease due to having close contact with their patients. Dental care settings carry the risk of 2019-nCoV-2 infection due to some factors: first, their procedures including face-to-face communication with patients and frequent exposure to the saliva, blood, and other body fluids, where a large number of droplets and aerosols could be generated, especially while using a high-speed handpiece or ultrasonic instruments, and second, the fact that the standard protective measures in daily clinical work are not effective enough to prevent the spread of COVID-19, especially when patients are in the incubation period (2-4).

Iran is one of the epicenters of this viral infection and one of the first countries that experienced the epidemic of this virus. However, no studies are available worldwide regarding the knowledge of healthcare workers, or dental professionals in particular, towards the new coronavirus infection and the measures of prevention.

2. Objectives

Therefore, this study was conducted to assess the knowledge of dental professionals towards COVID-19.

3. Methods

A cross-sectional study was conducted in the Oral and Maxillofacial Surgery (OMFS) Department of Islamic Azad University of Tehran, Iran. Undergraduate dental students, general practitioners (DDS), and board-certified dental specialists of 11 recognized specialties were considered eligible to take part in this study. The inclusion criteria were studying dentistry or being graduated from a dental school, being Iranian, and having the knowledge of the Persian language. The exclusion criterion was a lack of consent. Participants were anonymous, and no personal information was collected. The study protocol was approved by a University Committee (ethical code: IR.IAU.PS.REC.1399.062). The study started on March 25, 2020, and ended on March 31, 2020. At the beginning of conducting this study, the official number of confirmed COVID-19 cases, the number of deceased patients, and the number of recovered patients in Iran were 32332, 2378, and 11133, respectively.

The data were collected through a self-administered online questionnaire distributed to the participants by a specific link. The questionnaire was designed by a team of authors of the Buali Hospital OMFS Department after a rigorous literature review. It was sent to professionals to give their expert opinions about its simplicity, relevance, and importance. Then, a pilot study was conducted by selecting a small sample of health care professionals (n = 7) who gave their opinions on making the questionnaire more simple and shorter. The data of the pilot study were not used for the final analysis. Amendments from the participants were considered and integrated into the questionnaire. After a thorough discussion, the questionnaire was finalized by the authors and subsequently distributed to the participants for their responses. The validity of the questionnaire was assessed through the Delphi method. The reliability of the questionnaire was established by sending the questionnaire to 10 participants and resending it to the same 10 participants after a week. There was not a significant difference between the two assessments. The study instrument assessed the knowledge of the participants by asking questions about nature, etiology, symptoms, risk group, consequences, and source of transmission, prevention, and treatment of COVID-19 (Table 1). The mean time of response was 5 minutes and 42 seconds.

Table 1. The List of Questions and Their Correct Answersa
QuestionsCorrect Answer
1Did you research the new pandemic coronavirus?-
2Have you attended any meetings or lectures on the new coronavirus?-
3What is the most important source of information you use to get information about the new coronavirus?-
4What is the incubation period of the new coronavirus? (5-7)2-14 days
5Which of the following is not a sign of the new coronavirus? (6-10)Skin rash
6Which of the following is the possible origin of the new coronavirus? (6, 11)Bat
7Which of the following is involved in transmitting the coronavirus? (10)Air
8Which of the following is not a complication of the new coronavirus? (7, 8, 10, 12, 13)Gastrointestinal problems
9Which method is currently used to control the new coronavirus? (14)Antiviral and supportive treatments
10How to reduce the risk of transmission of the new coronavirus? (14, 15)Proper handwashing/covering the mouth while coughing or sneezing/avoiding direct contact with a patient
11Which of the following is not a high-risk group for the new coronavirus? (16)Children
12What is the new coronavirus diagnostic method? (17)PCR
13Which organs have the highest incidence of new coronavirus infections due to the higher number of receptors? (18, 19)Lung
14How long does the new coronavirus stay in the air? (20)3 hours
15Anyone with fever, cough, or difficulty breathing should be treated immediately and share their previous travel history with the medical staff (21).True
16According to the WHO guidelines on the new coronavirus, handwashing is only required if there is visible contamination (22).False
17Even in areas with a new coronavirus outbreak, the consumption of meat products is OK if cooked properly (23).True
18A treated person is immune to the new coronavirus (24).True
19It is necessary to disinfect the place of meat products sale and equipment used in it at least once a day.True
20The use of the influenza vaccine against the new coronavirus also provides immunity (25, 26).False
21Symptoms of a new coronavirus appear between 2 and 14 days after the initial exposure to the virus (10).True
22Handwashing with warm water is a must.False
23If soap is not available, it is enough to wash your hands with chlorine-containing water.False

Descriptive statistics were calculated for each question. The role of the associated factors was assessed using the chi-square test in SPSS 25 (IBM, Armonk, NY, USA). The level of significance was set at 0.05.

4. Results

A total of 1,331 individuals visited the website, and 778 of them completed the questionnaire. Of the respondents, 54.7% were males, and 44.2% were older than 40 years. Of them, 15.4% were dental students, 58.5% were general dentists, and 26.1% were specialists. The mean age of students was 24.13 years; they were 67 women and 53 men. The mean age of general practitioners was 42.32 years, including 204 females and 251 males. The mean age of specialists was 41.08 years, including 80 women and 123 men.

About 27% of the participants had attended meetings and lectures about the new coronavirus. The most important sources of individuals’ information were official websites (45.1%), followed by social networks (39.7%), news and media (13%), and finally, family members (1.2%). In other words, 85% of the cases used the two sources of official websites and social networks.

Overall, above 70% of the respondents answered correctly to most questions, except for the questions numbered 4, 7, 12, 18, 22, and 23 (Figure 1 and Table 2). Specifically, questions 12 (method of diagnosis) and 18 (immunity after contamination and treatment) received the smallest numbers of correct answers.

Percentages of correct answers to questions 4 to 23 in the whole sample (n = 778)
Table 2. Percentages of Correct Answers to Questions 4 to 23, as Well as Top Answers to Questions 1 to 3 in Different Jobs and Specialtiesa
QDental Students (N = 120)Dentists (N = 455)Specialist (N = 203)OMFS (N = 59)Public Health (N = 7)Radiology (N = 2)Pathology (N = 8)Pediatrics (N = 9)Restorative (N = 13)Orthodontics (N = 16)Prosthodontics (N = 25)Periodontics (N = 31)Endodontics (N = 15)Oral Disease (N = 20)P
1Yes (92.5)Yes (96.7)Yes (98.3)Yes (98.3)Yes (100)Yes (100)Yes (100)Yes (88.9)Yes (100)Yes (100)Yes (100)Yes (96.8)Yes (100)Yes (95)
2No (77.5)No (77.6)No (67.8)No (67.8)No (57.1)No (100)No (62.5)No (88.9)No (84.6)No (81.3)No (80)No (77.4)No (93.3)No (75)
3Social media (45)Official websites (43.5)Official websites (45.8)Official websites (45.8)Official websites (57.1)Official websites (50)Official websites (62.5)Official websites (55.6)Official websites (38.5)official websites (43.8)Social media (48)Official websites (58.1)Official websites (46.7)Official websites (65)

The chi-square test showed that age, specialization, and attendance at lectures and meetings did not play a role in grasping accurate information (all P values > 0.1). Men had less information than women (P = 0.014), and the sources of information were mostly official websites and social networks (P = 0.000).

Dental students knew the correct answer to question 10 (95%) significantly worse than dentists (99%) and specialists (99%, chi-square P < 0.05, detailed p values in Table 2). There was also a significant difference between dental students (8.3%), dentists (5.3%), and specialists (10.8%) in response to question 12 (PCR as the method of detection, Table 2). In question 15, dental students (71.7%) acted worse than dentists (87.3%) and specialists (85.2%, P < 0.05, detailed P values in Table 2). In question 23 (lack of soap), dental students (65.0%) and dentists (50.5%) acted much better than specialists (9.4%, P < 0.05, detailed P values in Table 2).

5. Discussion

Our findings indicated that a relatively high proportion of dentists and dental students had basic coronavirus protection and general knowledge. However, when the questions became more technical, the percentage of correct answers reduced. According to the social cognitive theory, behaviors are shaped by subjective norms, perceived behavioral control, and personal attitudes, which are influenced by personal knowledge and experience (27-29). Proper knowledge of a contagious disease can result in better attitudes and more effective practices towards protection and prevention; therefore, it is essential to have proper knowledge (30-32). This is of utmost importance as the willingness of healthcare professionals to treat patients depends on their attitude and knowledge. While most jobs are recommended to work from home (due to the pandemic situation), healthcare professionals should be even more willing to attend clinics and hospitals, putting themselves at even higher risk of infection (33). Thus, their willingness to treat should be properly high, and they should be able to protect themselves and their patients from cross-infection appropriately. This higher willingness can itself result in healthcare-associated infections that can increase the mortality and costs (28), again needing the knowledge to prevent cross-infection.

An important factor in COVID-19 is its very long latency period. About half of the respondents did not know the correct answer. Another important information that was answered incorrectly by about half of the cases was the transmission medium, i.e., air. Many participants selected the oral-fecal choice or other less relevant ones. Immunity against the coronavirus was one of the most difficult questions. Most respondents chose no immunity. However, coronavirus might still induce short-term or even moderate-term immunity in some people (24). Two other questions with poor answers were related to handwashing, which showed that not a proper knowledge of handwashing might exist among dentists. Handwashing is extremely important in controlling diseases such as MERS (28) or COVID-19 and should be taken seriously.

The knowledge of dental students, dentists, and specialists was rather similar in terms of most questions. Questions that needed a greater education level (like PCR) were answered better by specialists and/or dentists than by dental students. Another reason could be that dental students used social media as their main source of information, while dentists and specialists used official websites as their main source. Since there is no literature at all in this regard, we cannot compare our results with other studies.

This study was limited by some factors. The sample size of this pilot study was not based on any calculations. Many of the questions asked had ambiguous answers at the time of assessment or even months after it. Therefore, it was not possible even for experts to know the correct answers to many questions at the time. Although it seems that the comparison of dental students with dental specialists might not be completely rational, it should be noted that both groups were similarly exposed to a major source of education towards COVID-19, i.e., media. Immunity against COVID-19 is temporary, and this is being shown by every new research published in this regard. However, it is not very realistic that we expect dental professionals know about it, especially at earlier times of disease spread. The answers to some questions might not be correct, such as bat as the source of the disease, which is quite debatable now, and the coronavirus stays in the air for three hours only in laboratory conditions using specialized devices to produce aerosols and not in normal situations.

Regarding the 13th question, it is suggested that salivary glands can be affected by this disease (34). There are still many points to debate since there are still many uncovered issues on COVID-19. For example, gastrointestinal involvement is reported in COVID-19 (35). Future studies are warranted to conduct more accurate surveys. The generalizability of our findings was limited to Iranian dentists in the first three months of COVID-19 spread. Indeed, day by day, more facts are revealed about this disease, and dentists and other health workers are more and more educated in this regard. Therefore, future studies can rely on more technical and more comprehensive surveys.

5.1. Conclusions

The knowledge of dentists, dental students, and specialists towards SARS-CoV-2 is generally rather good, except for more technical questions that need more education (especially regarding handwashing). The most important sources of information were official websites and social media. Dentists, dental students, and specialists acted almost similarly in the case of most questions, except for more difficult ones.


  • 1.

    De Ceukelaire W, Bodini C. We need strong public health care to contain the global corona pandemic. Int J Health Serv. 2020;50(3):276-7. doi: 10.1177/0020731420916725. [PubMed: 32188308]. [PubMed Central: PMC7140782].

  • 2.

    Peng X, Xu X, Li Y, Cheng L, Zhou X, Ren B. Transmission routes of 2019-nCoV and controls in dental practice. Int J Oral Sci. 2020;12(1):9. doi: 10.1038/s41368-020-0075-9. [PubMed: 32127517]. [PubMed Central: PMC7054527].

  • 3.

    Meng L, Hua F, Bian Z. Coronavirus disease 2019 (COVID-19): Emerging and future challenges for dental and oral medicine. J Dent Res. 2020;99(5):481-7. doi: 10.1177/0022034520914246. [PubMed: 32162995]. [PubMed Central: PMC7140973].

  • 4.

    Guo H, Zhou Y, Liu X, Tan J. The impact of the COVID-19 epidemic on the utilization of emergency dental services. J Dent Sci. 2020. doi: 10.1016/j.jds.2020.02.002. [PubMed: 32296495]. [PubMed Central: PMC7156222].

  • 5.

    Lauer SA, Grantz KH, Bi Q, Jones FK, Zheng Q, Meredith HR, et al. The incubation period of coronavirus disease 2019 (COVID-19) from publicly reported confirmed cases: Estimation and application. Ann Intern Med. 2020;172(9):577-82. doi: 10.7326/M20-0504. [PubMed: 32150748]. [PubMed Central: PMC7081172].

  • 6.

    Guo YR, Cao QD, Hong ZS, Tan YY, Chen SD, Jin HJ, et al. The origin, transmission and clinical therapies on coronavirus disease 2019 (COVID-19) outbreak - an update on the status. Mil Med Res. 2020;7(1):11. doi: 10.1186/s40779-020-00240-0. [PubMed: 32169119]. [PubMed Central: PMC7068984].

  • 7.

    Lai CC, Shih TP, Ko WC, Tang HJ, Hsueh PR. Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) and coronavirus disease-2019 (COVID-19): The epidemic and the challenges. Int J Antimicrob Agents. 2020;55(3):105924. doi: 10.1016/j.ijantimicag.2020.105924. [PubMed: 32081636]. [PubMed Central: PMC7127800].

  • 8.

    Huang C, Wang Y, Li X, Ren L, Zhao J, Hu Y, et al. Clinical features of patients infected with 2019 novel coronavirus in Wuhan, China. Lancet. 2020;395(10223):497-506. doi: 10.1016/s0140-6736(20)30183-5.

  • 9.

    Rodriguez-Morales AJ, Cardona-Ospina JA, Gutierrez-Ocampo E, Villamizar-Pena R, Holguin-Rivera Y, Escalera-Antezana JP, et al. Clinical, laboratory and imaging features of COVID-19: A systematic review and meta-analysis. Travel Med Infect Dis. 2020;34:101623. doi: 10.1016/j.tmaid.2020.101623. [PubMed: 32179124]. [PubMed Central: PMC7102608].

  • 10.

    Rothan HA, Byrareddy SN. The epidemiology and pathogenesis of coronavirus disease (COVID-19) outbreak. J Autoimmun. 2020;109:102433. doi: 10.1016/j.jaut.2020.102433. [PubMed: 32113704]. [PubMed Central: PMC7127067].

  • 11.

    Zhou P, Yang XL, Wang XG, Hu B, Zhang L, Zhang W, et al. A pneumonia outbreak associated with a new coronavirus of probable bat origin. Nature. 2020;579(7798):270-3. doi: 10.1038/s41586-020-2012-7. [PubMed: 32015507]. [PubMed Central: PMC7095418].

  • 12.

    Wu F, Zhao S, Yu B, Chen YM, Wang W, Song ZG, et al. A new coronavirus associated with human respiratory disease in China. Nature. 2020;579(7798):265-9. doi: 10.1038/s41586-020-2008-3. [PubMed: 32015508]. [PubMed Central: PMC7094943].

  • 13.

    Shi H, Han X, Jiang N, Cao Y, Alwalid O, Gu J, et al. Radiological findings from 81 patients with COVID-19 pneumonia in Wuhan, China: A descriptive study. Lancet Infect Dis. 2020;20(4):425-34. doi: 10.1016/s1473-3099(20)30086-4.

  • 14.

    Cascella M. Features, evaluation, and treatment of coronavirus (COVID-19). StatPearls Publishing; 2020.

  • 15.

    Hellewell J, Abbott S, Gimma A, Bosse NI, Jarvis CI, Russell TW, et al. Feasibility of controlling COVID-19 outbreaks by isolation of cases and contacts. Lancet Glob Health. 2020;8(4):e488-96. doi: 10.1016/s2214-109x(20)30074-7.

  • 16.

    Ruan Q, Yang K, Wang W, Jiang L, Song J. Clinical predictors of mortality due to COVID-19 based on an analysis of data of 150 patients from Wuhan, China. Intensive Care Med. 2020;46(5):846-8. doi: 10.1007/s00134-020-05991-x. [PubMed: 32125452]. [PubMed Central: PMC7080116].

  • 17.

    Ai T, Yang Z, Hou H, Zhan C, Chen C, Lv W, et al. Correlation of Chest CT and RT-PCR testing for coronavirus disease 2019 (COVID-19) in China: A report of 1014 cases. Radiology. 2020;296(2):E32-40. doi: 10.1148/radiol.2020200642. [PubMed: 32101510]. [PubMed Central: PMC7233399].

  • 18.

    Wan Y, Shang J, Graham R, Baric RS, Li F. Receptor recognition by the novel coronavirus from wuhan: An analysis based on decade-long structural studies of SARS coronavirus. J Virol. 2020;94(7). doi: 10.1128/JVI.00127-20. [PubMed: 31996437]. [PubMed Central: PMC7081895].

  • 19.

    Jin Y, Yang H, Ji W, Wu W, Chen S, Zhang W, et al. Virology, epidemiology, pathogenesis, and control of COVID-19. Viruses. 2020;12(4). doi: 10.3390/v12040372. [PubMed: 32230900]. [PubMed Central: PMC7232198].

  • 20.

    van Doremalen N, Bushmaker T, Morris D, Holbrook M, Gamble A, Williamson B, et al. Aerosol and surface stability of SARS-CoV-2 as compared with SARS-CoV-1. N Engl J Med. 2020. doi: 10.1101/2020.03.09.20033217.

  • 21.

    Borasio GD, Gamondi C, Obrist M, Jox R, For The Covid-Task Force Of Palliative Ch. COVID-19: Decision making and palliative care. Swiss Med Wkly. 2020;150:w20233. doi: 10.4414/smw.2020.20233. [PubMed: 32208494].

  • 22.

    World Health Organization. Rational use of personal protective equipment for coronavirus disease (COVID-19): Interim guidance. World Health Organization; 2020.

  • 23.

    Shariatifar N, Molaee-aghaee E. Novel coronavirus 2019 (COVID‐19): Important tips on food safety. J Food Saf Hygiene. 2020. doi: 10.18502/jfsh.v5i1.3886.

  • 24.

    Aldridge RW, Lewer D, Beale S, Johnson AM, Zambon M, Hayward AC, et al. Seasonality and immunity to laboratory-confirmed seasonal coronaviruses (HCoV-NL63, HCoV-OC43, and HCoV-229E): Results from the Flu Watch cohort study. Wellcome Open Res. 2020;5. doi: 10.12688/wellcomeopenres.15812.1.

  • 25.

    Chen L, Hao G. The role of angiotensin-converting enzyme 2 in coronaviruses/influenza viruses and cardiovascular disease. Cardiovasc Res. 2020. doi: 10.1093/cvr/cvaa093. [PubMed: 32267499]. [PubMed Central: PMC7184394].

  • 26.

    Liu C, Zhou Q, Li Y, Garner LV, Watkins SP, Carter LJ, et al. Research and Development on Therapeutic Agents and Vaccines for COVID-19 and Related Human Coronavirus Diseases. ACS Cent Sci. 2020;6(3):315-31. doi: 10.1021/acscentsci.0c00272. [PubMed: 32226821]. [PubMed Central: PMC7094090].

  • 27.

    Conner M, Armitage CJ. Extending the theory of planned behavior: A review and avenues for further research. J Appl Soc Psychol. 1998;28(15):1429-64. doi: 10.1111/j.1559-1816.1998.tb01685.x.

  • 28.

    Alfahan A, Alhabib S, Abdulmajeed I, Rahman S, Bamuhair S. In the era of corona virus: health care professionals' knowledge, attitudes, and practice of hand hygiene in Saudi primary care centers: A cross-sectional study. J Community Hosp Intern Med Perspect. 2016;6(4):32151. doi: 10.3402/jchimp.v6.32151. [PubMed: 27609728]. [PubMed Central: PMC5016750].

  • 29.

    Ajzen I, Driver BL. Prediction of leisure participation from behavioral, normative, and control beliefs: An application of the theory of planned behavior. Leisure Sciences. 1991;13(3):185-204. doi: 10.1080/01490409109513137.

  • 30.

    Khosravanifard B, Rakhshan V, Ghasemi M, Pakdel A, Baradaran-Eghbal S, Sheikholeslami R, et al. Tehran dentists' self-reported knowledge and attitudes towards HIV/AIDS and observed willingness to treat simulated HIV-positive patients. East Mediterr Health J. 2012;18(9):928-34. doi: 10.26719/2012.18.9.928. [PubMed: 23057385].

  • 31.

    Khosravanifard B, Rakhshan V, Najafi-Salehi L, Sherafat S. Tehran dentists' knowledge and attitudes towards hepatitis B and their willingness to treat simulated hepatitis B positive patients. East Mediterr Health J. 2014;20(8):498-507. [PubMed: 25150357].

  • 32.

    Khosravanifard B, Rakhshan V, Sherafat S, Najafi-Salehi L. Risk factors influencing dentists' hepatitis B-related knowledge and attitudes and their willingness to treat hepatitis B positive patients. East Mediterr Health J. 2015;21(1):54-61. doi: 10.26719/2015.21.1.54. [PubMed: 25907193].

  • 33.

    Bai Y, Wang X, Huang Q, Wang H, Gurarie D, Ndeffo-Mbah M, et al. SARS-CoV-2 infection in health care workers: A retrospective analysis and a model study. medRxiv. 2020. doi: 10.1101/2020.03.29.20047159.

  • 34.

    Xu J, Li Y, Gan F, Du Y, Yao Y. Salivary glands: Potential reservoirs for COVID-19 Asymptomatic Infection. J Dent Res. 2020;99(8):989. doi: 10.1177/0022034520918518. [PubMed: 32271653].

  • 35.

    Tian Y, Rong L, Nian W, He Y. Review article: Gastrointestinal features in COVID-19 and the possibility of faecal transmission. Aliment Pharmacol Ther. 2020;51(9):843-51. doi: 10.1111/apt.15731. [PubMed: 32222988]. [PubMed Central: PMC7161803].

Copyright © 2020, Author(s). This is an open-access article distributed under the terms of the Creative Commons Attribution-NonCommercial 4.0 International License ( which permits copy and redistribute the material just in noncommercial usages, provided the original work is properly cited.
mohamad mehdizadeh
2020-08-21 07:02:16
very useful article