Surface disinfection and protective masks for SARS‐CoV‐2 and other respiratory viruses: A review by SIdP COVID‐19 task force

Abstract Objectives Primary focused question for this systematic review (SR) was “Which is the evidence about surfaces decontamination and protection masks for SARS‐Cov‐2 in dental practice?” Secondary question was “Which is the evidence about surfaces decontamination and protection masks against airborne pathogens and directly transmitted viral pathogens causing respiratory infections?” Materials and Methods PRISMA guidelines were used. Studies on surface decontamination and protective masks for SARS‐CoV‐2 in dental practice were considered. Studies on other respiratory viruses were considered for the secondary question. Results No studies are available for SARS‐CoV‐2. Four studies on surface disinfection against respiratory viruses were included. Ethanol 70% and sodium hypochlorite 0,5% seem to be effective in reducing infectivity by > 3log TCID. Four RCTs compared different types of masks on HCW. The single studies reported no difference for laboratory‐diagnosed influenza, laboratory‐diagnosed respiratory infection, and influenza‐like illness. A meta‐analysis was not considered appropriate. Conclusions There is lack of evidence on the efficacy of surface disinfection and protective masks to reduce the spread of SARS‐CoV‐2 or other respiratory viruses in dentistry. However, the consistent use of respirator and routine surface disinfection is strongly suggested. There is urgent need of data on the efficacy of specific protection protocols for dental HCW against viral infections.


| INTRODUC TI ON
On January 7, 2020, a novel coronavirus called 2019-nCov was identified in patients affected by pneumonia of unknown etiology in Wuhan, China. The virus was renamed SARS-CoV-2, and the clinical disease, COVID-19. On August 2020, more than 23.4 million of people were affected all over the word. Healthcare workers (HCWs) account for a significant proportion of infections (Chou et al., 2020).
The principal route of transmission for the SARS-CoV-2 is direct contact with respiratory droplets (>5-10 μm), and the other route is indirect contact through fomites (Chan et al., 2020;Li et al., 2020a).
The airborne transmission (droplet nuclei, <5-10 μm) is possible but not demonstrated (Meselson, 2020), even if the viral RNA was found in the aerosol of different hospital areas . The transmission routes are similar to other respiratory viruses (e.g., SARS-CoV, MERS).
In general, respiratory droplets represent a direct source of infection for respiratory viruses and also rapidly fall creating fomites near the infected subjects (<1 m). Contrary droplet nuclei may remain in the air for a long period and could be inhaled, thus potentially represent a source of infection at greater distance (>1 m). The SARS-CoV-2 could remain viable in the aerosol for hours (Lednicky et al., 2020;Doremalen et al., 2020) and infected droplets could precipitate, thus contaminating the operative surfaces . Therefore, in a dental setting, HCWs are exposed to infection risk through direct contact with respiratory droplets, but also through indirect contact with contaminated surfaces or instruments (Ionescu et al., 2020;Peng et al., 2020;. Additionally, dental HCWs are exposed also to airborne produced during the usually performed aerosol-generating procedures (AGPs). This observation raised a debate on airborne transmission for SARS-CoV-2 and other respiratory viruses in a dental setting.
Although dental HCWs could be considered at higher risk of respiratory infections due to the characteristic of the dental setting and the performed procedures, no conclusive data are available demonstrating the increased risk (Samaranayake & Peiris, 2004).
The surface decontamination procedures alongside the use of personal protective equipment (PPE), including protective mask, are effective in reducing the infection among HCW, especially during outbreaks (Verbeek et al., 2020). These approaches for infection control are routinely used in the dental practice, but the evaluation of their efficacy during SARS-CoV-2 spread should be examined.
The appropriate implementation of PPE and disinfection procedures raises relevant medico-legal issues for dental professionals and legal challenges for authorities deputed to provide guidance on correct use and adequate supplies (Dyer, 2020).
The primary aim was to review the evidence about surface disinfection and protection mask usage in dental practice for SARS-CoV-2. Due to lack of evidence, we also add a secondary aim to review the evidence for other directly transmitted viral pathogens that cause respiratory infections.

| Protocol and focused question
The protocol for this SR was prepared according to PRISMA guidelines (Hutton et al., 2015). The focused question was "Which is the evidence about surfaces decontamination and protection masks for SARS-Cov-2 in dental practice?" Materials and Methods: PRISMA guidelines were used. Studies on surface decontamination and protective masks for SARS-CoV-2 in dental practice were considered.
Studies on other respiratory viruses were considered for the secondary question.

Results:
No studies are available for SARS-CoV-2. Four studies on surface disinfection against respiratory viruses were included. Ethanol 70% and sodium hypochlorite 0,5% seem to be effective in reducing infectivity by > 3log TCID. Four RCTs compared different types of masks on HCW. The single studies reported no difference for laboratory-diagnosed influenza, laboratory-diagnosed respiratory infection, and influenza-like illness. A meta-analysis was not considered appropriate.

Conclusions:
There is lack of evidence on the efficacy of surface disinfection and protective masks to reduce the spread of SARS-CoV-2 or other respiratory viruses in dentistry. However, the consistent use of respirator and routine surface disinfection is strongly suggested. There is urgent need of data on the efficacy of specific protection protocols for dental HCW against viral infections.

K E Y W O R D S
COVID-19, Personal protection equipment, SARS-CoV-2, Surface disinfection TA B L E 1 Studies reporting the efficacy of different disinfectants on surfaces in terms of viral titer reduction expressed as virus log10 reduction factor TCID 50

| Eligibility criteria and information sources
All the studies reporting evidence regarding the efficacy of surface decontamination procedures and protective mask usage for SARS-CoV-2 in dental practice were considered. Only English-language manuscripts were included. Searches were conducted on PubMed and Embase on 24, August 2020. Additionally, the Cochrane special section for COVID-19 and the references of the included studies were checked also. Full-text assessment of all the articles on COVID-19 published on dental journals or about dental procedures was performed. For details regarding search strategy, study selection, and data collection process, see supporting information (Appendix S1).
As this search did not provide studies on SARS-CoV-2 in dentistry, we reviewed literature on other viral pathogens causing respiratory infections using a specific search strategy (Appendix S1). All the studies comparing the efficacy of different disinfection agents on inanimate surfaces or using carrier test in terms of viral load reduction/inactivation were considered.
Randomized clinical trials comparing the efficacy of different protective masks in preventing respiratory infections among HCWs in terms of laboratory-confirmed infection were also included. The references of previous SR and included studies were checked also for additional titles. Only English-language manuscripts were included.

| RE SULTS
The search for surface disinfection and protective mask usage in dental practice for SARS-CoV-2 yields 8,749 titles; however, no study   Dental HCWs are in close contact with patient mouths, very frequently performing AGPs (i.e., sonic/ultrasonic device). The SARS-CoV-2 RNA was found in the saliva of infected patients Zhang et al., 2020); thus, saliva could be a source of infection . The aerosols generated during an AGP are mixed with patient saliva/blood and is contaminated by bacteria and viruses (Cleveland et al., 2016;Harrel & Molinari, 2004) acting thus as a carrier of infection (Ionescu et al., 2020;Zemouri et al., 2017;. Therefore, dental HCWs and patients attending dental procedures could be considered potentially at risk of infections due to direct contact with respiratory droplets, indirect contact with fomites, and inhalation of droplet nuclei.

| D ISCUSS I ON
In a clinical perspective, the identification of COVID-19 patients is a key factor in dental settings. Although the telephonic triage has been suggested to potentially screen positive patients, two possible scenarios may be identified. The first, as suggested by epidemiology reports on COVID-19 (Li et al., 2020a), is a contagious asymptomatic patient requiring dental treatments, not yet diagnosed for SARS-CoV-2. Under these conditions, the use of PPE appears critical to reduce the possible risk of infection (Dugré et al., 2020;. The secondary focused question was on the use of surface disinfection and protective masks to protect against airborne pathogens and directly transmitted viral pathogens that cause respiratory infections. Evidence of biocidal agents against other coronaviruses could be retrieved from a recent systematic review. In carrier tests, ethanol (70%), sodium hypochlorite (0,1%), and glutaraldehyde (2%) for 1 min were effective to reduce endemic human coronavirus (HCoV) infectivity by > 3log TCID 50/ml in suspension tests, and ethanol (78%-95%), 2-propanol (70%-100%), glutaraldehyde (0.5%-2.5%), formaldehyde (0.7%-1%), and povidone-iodine (0.23%-1%) reduced SARS-CoV infectivity by > 3log TCID 50/ml (Kampf, 2020b;Kampf et al., 2020a).
In our review, suspension test studies were not considered. We evaluated only carrier test or test on inanimate surface because these better simulate a real clinical setting. Only four studies testing different disinfectants on different surfaces (glass, plastic, stainless) were included. Data from single studies suggest that ethanol 70%, sodium hypochlorite 0,5%, and GDA 2% were effective in reducing the viral titer of > 3log TCID 50/ml for type 5 adenovirus, HCov 229E, and type 3 parainfluenza virus (Becker et al., 2017;Jeong et al., 2010;Rabenau et al., 2014;Sattar et al., 1989).

Very recently, European Centre for Disease Prevention and Control
(ECDC) suggested to use 0.05% sodium hypochlorite or 70% ethanol for surface disinfection in a healthcare setting (ECDC, 2020). The use of 0.05% sodium hypochlorite instead of higher concentrations was suggested by ECDC to reduce irritant effects on the mucosae. It is mandatory to consider that glutaraldehyde usage as disinfectant agent is not allowed in most European countries, and it should be kept in mind that chronic glutaraldehyde utilization may expose to important side effects, including sensitization of skin and respiratory diseases, and a potential carcinogenic activity (Takigawa & Endo, 2006).
Considering all these elements, ethanol 70% or sodium hypochlorite 0.05% could be suggested for surface disinfection.
Four RCTs comparing the efficacy of different masks against other respiratory viruses were included (Loeb et al., 2009;MacIntyre et al., 2011;MacIntyre et al., 2013;Radonovich et al., 2019). All the included studies compared surgical mask versus N95 fit-tested respirators in HCWs. In a RCT, not-fit-tested N95 was used also, while another RCT proposed a targeted use of fit-tested N95 respirator.
Even if data are scanty and controversial, the reported outcomes in the single studies provided a trend of similar efficacy in terms of laboratory-diagnosed influenza, laboratory-diagnosed respiratory viral infections, and ILI for surgical mask versus fit-tested N95 respirator. However, CRI could be bacteria-related and not virus-related and this might be not properly explored. All the included studies are performed also in hospital settings but no included trial has a proper control group to monitor the infection source outside, thus limiting the possibility to extend these findings to dental setting.
The rationale to use a filtering facepiece respirators (such as N95, KN95, and FFP2), rather than a surgical mask, is also due to the higher capability in protection against the small aerosol particles (<1 μm) (Bałazy et al., 2006;Qian et al., 1998) (Jefferson et al., 2011), and this could have reduced the protective efficacy hindering the differences with the surgical masks. From the overall assessment of the evidence, the use of respirators for dental HCWs seems to be indicated in protecting against respiratory viruses, since dental office is a specific medical setting in which HCWs are very often exposed to potentially infected aerosol.
It should be keep also into account that availability of filtering facepiece respirators may be difficult during an outbreak. The possible disinfection of these respirators applying different procedures, including ionized hydrogen peroxide  or ultraviolet C light (Cadnum et al., 2020) or combinations (Bergman et al., 2010), has been proposed. However, reported outcomes are controversial and heterogeneous, thus suggesting caution in terms of routine applicability.
It is mandatory to underline that protective mask usage has to be considered alongside other PPE (i.e., gowns, gloves). The whole protocol appears more important than the single protective item.
Although is difficult to retrieve specific information in dental literature (Li et al., 2020b;Volgenant et al., 2020), the importance of PPE during an outbreak has been described in case-control and retrospective cohort studies, underlying the importance in using masks, gowns, and gloves for reducing risk of infection compared with their inconsistent use (Verbeek et al., 2020). Unfortunately, it is not possible to clearly assess which is the best PPE procedure or the perfect combination. The majority of the available information is related to laboratory simulative studies useful for setting the equipment physical standard requirements. However, the experimental condition of these simulations could be really different from the clinical settings.
The aforementioned limitations in testing strongly reduce the possible generalizability of present information. Based on the previous evaluation, WHO recommended wearing gloves, masks, goggles, face shields, and long-sleeved gowns adding a filtering facepiece respirator only during an AGP on a COVID-19-positive patient (WHO, 2020).

| CON CLUS I ON S AND RECOMMENDATIONS
• No direct evidence is available for surface disinfection and protective masks for SARS-CoV-2 or other respiratory viruses in dental setting.
• Although direct evidence is missing, application of ethanol 70% or sodium hypochlorite 0,5% for 1 min should be considered effective to reduce SARS-CoV-2 or respiratory virus infectivity over surfaces.
• Surgical masks may be not adequate to prevent respiratory virus transmission to dental HCWs.
• Although limited in terms of consistency, evidence showed that a proper use of filtering facepiece respirators should be recommended especially performing an AGP.
• There is the urgent need to test efficacy of specific protection protocols for dental HCWs for SARS-CoV-2 and other respiratory viruses.

CO N FLI C T O F I NTE R E S T
The authors have nothing to disclose.

PE E R R E V I E W
The peer review history for this article is available at https://publo ns.com/publo n/10.1111/odi.13646.