SARS-CoV-2 is excreted in the oral cavity and can be spread via aerosols. Aerosol generating procedures in dental health care can increase the risk of transmission of the virus. Due to the risk of infection of both dental healthcare workers and patients, additional infection control measures for all patients are strongly recommended when providing dental health care. Consideration should be given to which infection control measures are necessary when providing care in both the current situation and in the future.
Elimination of the reservoir
- Part of the demand of dental health care can be met by telephone, email or videoconferences (Guo, Wu, & Xie, 2020; Meng et al., 2020b). A detailed patient history, possibly accompanied by photographs or video conferencing, can aid the primary management of dental emergencies. Urgent care can be managed by prescribing analgesia, antiseptics or as a last option antibiotics (Ather, Patel, Ruparel, Diogenes, & Hargreaves, 2020). These modern techniques can also be applied when providing preventive dental health care (Darwish, 2020; Mallineni et al., 2020).
- In an area where widespread transmission has not been established, triage can aid in estimating risks of transmission of SARS-CoV-2. Individuals with a travel history to areas with ongoing transmission or individuals with recent exposure to SARS-CoV-2-positive individuals should be considered as a high risk for serving as a source of transmission. Moreover, individuals showing signs and symptoms of COVID-19 (e.g. coughing or a fever; see above) should also be considered as high risk for transmission. DHCWs who comply with criteria as described above should be considered as high risk and therefore should not be present in the dental clinic.
- For detecting patients to who care can be provided with limited risk of transmission with SARS-CoV-2, triage is applicable (Alharbi, Alharbi, & Alqaidi, 2020; Ayebare, Flick, Okware, Bodo, & Lamorde, 2020; Izzetti et al., 2020; Prati, Pelliccioni, Sambri, Chersoni, & Gandolfi, 2020). Dental health care for patients showing signs and symptoms of COVID-19 should be limited to urgent care and can only be provided in a clinic with full protective measures. DHCWs have to keep in mind that triage is currently unable to differentiate asymptomatic or presymptomatic patients from unaffected individuals. Reliable, simple and cheap rapid tests can assist in determining to who dental health care can be provided without additional measures (Khurshid et al., 2020).
- When providing care is indispensable, elimination of (secondary) infectious reservoirs is essential in preventing transmission. Both hand hygiene and hygiene of surfaces have always been important measures against the spread of viruses in society and health care; this applies to SARS-CoV-2 as well (Lotfinejad, Peters, & Pittet, 2020; Lynch, Mahida, Oppenheim, & Gray, 2020; Nicolaides, Avraam, Cueto-Felgueroso, González, & Juanes, 2020; Ran et al., 2020). It is important to realise that DHCWs should prevent touching their own face, both with and without personal protective equipment (PPE) (Elder, Sawyer, Pallerla, Khaja, & Blacker, 2014). Cleaning removes the virus mechanically and disinfection inactivates the virus. Surfaces that may be contaminated with SARS-CoV-2 can effectively be disinfected within 1 min by applying at least 62% alcohol, 0.5% hydrogen peroxide or 1,000 ppm (0.1%) sodium hypochlorite (Kampf, Todt, Pfaender, & Steinmann, 2020). Effective disinfection with different alcohol-based hand rub formulations and lower dilutions of alcohol has also been reported (Kratzel et al., 2020).
- The procedures for cleaning, disinfection and sterilisation of instruments can be performed as described in regularly applicable guidelines in dentistry (Kohn et al., 2003). However, mechanical cleaning is strongly recommended (automated washer disinfectors) to prevent transmission by, for example, splashing during cleaning. Cleaning and/or disinfection should also include all horizontal surfaces in the treatment room and all other items and locations in the clinic that could have been touched by the patient (Kampf, Scheithauer, Lemmen, Saliou, & Suchomel, 2020).
Engineering controls: isolating DHCWs from the hazard
- The air in the treatment room after an aerosol generating procedure should be regarded as contaminated. Dispersion of the virus throughout the dental clinic should be avoided, even though it is currently unknown whether the amount of virus particles in the air after an aerosol generating procedure in dental health care can exceed the infectious dose. Therefore, working under negative air pressure would be preferable (Cheong & Phua, 2006). Clean air will be drawn from less contaminated areas towards the treatment room. The active exhaust flow from the contaminated treatment room leads to removal of possible pathogens from the air.
- In most dental clinics, working under negative air pressure is not possible. Sufficient ventilation in the room (Meng et al., 2020a) will dilute the virus load (Stockwell et al., 2019). On the one hand, mechanical ventilation, possibly enhanced, can significantly increase the expulsion of air. On the other hand, natural ventilation can be improved by active ventilation and, if possible, create a draught through the room (Escombe, Ticona, Chávez-Pérez, Espinoza, & Moore, 2019). Research data on the required duration of ventilation regarding SARS-CoV-2 in the dental clinic is not yet available. A case report suggested the spread of SARS-CoV-2 virus particles via droplet transmission prompted by air-conditioned ventilation (Lu et al., 2020). Therefore, potentially infected air should not be transported to people in the vicinity of the clinic.
- Some procedures do not require direct patient contact, for example scheduling of appointments. Indicating at which distance interaction is recognised as safe may be considered or installing physical barriers at the front desk, for example clear partitions. The interior of the dental clinic should be assessed and if necessary rearranged to allow for maintaining a safe distance, for example rearranging the waiting area.
Administrative controls: changing the way DHCWs organise their work
- The routing within the dental clinic should be arranged in such way that both DHCWs and patients are able to maintain distance from each other when DHCWs are not wearing PPE. Social distancing between DHCWs should also be maintained when not caring for a patient, for example when changing clothes or during breaks.
- Many infection control measures require changes in behaviour (Kretzer & Larson, 1998). Therefore, extra attention to (the behaviour of) the team is imperative and should be aimed at creating awareness to the adjusted procedures in order to prevent contamination between DHCWs. It is important to provide them with appropriate information, education and training and to provide sufficient resources to promote the behavioural changes.
- During dental treatment, the virus load in aerosols can be reduced by applying a leakproof rubber dam (Cochran, Miller, & Sheldrake, 1989; Rørslett Hardersen, Enersen, Kristoffersen, Ørstavik, & Sunde, 2019; Samaranayake, Reid, & Evans, 1989). The work field should be disinfected after the application of rubber dam. Furthermore, apart from reducing the microbial load from aerosols, rubber dam can also contribute to reducing splashes (Dahlke et al., 2012).
- Aerosol dispersion should be minimised by adjusting dental treatment procedures, for example by using hand instruments instead of water-cooled instruments or ultrasonic cleaning devices (Harrel, Barnes, & Rivera-Hidalgo, 1998). In addition, adequate saliva as well as aerosol extraction using high volume evacuation is important to minimise aerosol production (Devker et al., 2012; Narayana, Mohanty, Sreenath, & Vidhyadhari, 2016). Procedures that provoke gag reflexes or coughing should be avoided if possible (Meng et al., 2020a).
- Thirty minutes after aerosol formation, virus particles and bacteria can still be detected in the air of the treatment room (Bennett et al., 2000; Nikitin et al., 2014). Transmission to unprotected DHCWs in between treatments as well as to the next patient should be prevented. Alternatively, to waiting at least 30 min between patients, sufficient ventilation may be applied (more information under Engineering controls).
- Recent publications suggested that rinsing the oral cavity with hydrogen peroxide (1% H2O2) may be useful in reducing the risk of transmission of SARS-CoV-2 via aerosols (Ather et al., 2020; Peng et al., 2020). However, since the viral load is high in the throat, in the nose, on the tongue and in the saliva (Liu et al., 2011; Xu et al., 2020; Zou et al., 2020), the oral cavity will soon be recontaminated after rinsing. Povidine-iodine has been suggested to be useful for both oral and nasal disinfection against SARS-CoV-2 (Kirk-Bayley, Challacombe, Sunkaraneni, & Combes, 2020; Loftus, Dexter, Parra, & Brown, 2020; Rørslett Hardersen et al., 2019). A systematic literature review reported that rinsing with all kinds of other orally applied disinfectants reduces the microbiological load in aerosols generated during dental healthcare procedures (Marui et al., 2019), but it is unclear whether this reduction is clinically relevant for prevention of SARS-CoV-2 transmission. In vitro studies on chlorhexidine showed that it insufficiently inactivates SARS-CoV-2 (G. Kampf, Scheithauer, et al., 2020).
Protection of the DHCW with PPE
- Since the respiratory tract is the main portal of entry of the virus, the respiratory tract should be shielded (Jin et al., 2020). Therefore, the recommendation is to wear respiratory protection during aerosol generating procedures in patients infected with SARS-CoV-2 (WHO, 2020). These respiratory protective devices (filtering half masks: FFP-2/ N95/ KN95) filter particles significantly more effectively and have a better fit compared to regular medical face masks (type IIR, fluid resistant). PPE should protect the patient as well as fellow DHCWs against the micro-organisms exhaled by the user. Therefore, a mask with an exhalation valve should not be worn in dental health care, as it does not protect against splashes and respiratory micro-organisms from the user are released via the valve. It is essential that PPE complies with international standards for example European standard EN 149:2001 + A1: 2009 for respirators (British_Standards_Institution, 2011, 2019). In research on protection against fine particles, N95-equivalent respirators showed 9% total leakage, whereas for medical face masks leakage was 22%–35% (Steinle et al., 2018). It should be noted that medical face masks are designed to protect the patient against the exhaled air from the DHCW and do not protect DHCWs against aerosols. In a systematic review, the use of respirators was compared with medical face masks and was not associated with a lower risk of laboratory-confirmed influenza. The authors therefore suggested that these respirators should not be recommended for general public or non-high-risk medical staff, who are not in close contact with influenza patients or suspected patients (Long et al., 2020). Moreover, the effectiveness of respirators strongly depends on the proper intended use (Noti et al., 2012). The use of respirators significantly reduces the risks, but does not completely eliminate them. Clinical studies on the efficacy of masks in dentistry concerning virus protection have not been performed yet. The availability and prioritisation of PPE may influence which protection may be used within a dental clinic.
- The mucous membranes of the eyes are also a possible portal of entry (Adhikari et al., 2020). Therefore, goggles or a face shield should be used during treatment. The advantage of a face shield is its protection of mask from splashes (Lindsley, Noti, Blachere, Szalajda, & Beezhold, 2014).
- Transmission via surfaces like clothing can be prevented by careful behaviour (no touch) or by wearing a splash-proof long-sleeved apron over standard protective clothing. This apron should be considered contaminated after an aerosol generating treatment and should not be touched during treatment and should be discarded immediately after leaving the treatment room. All skin and other body parts left uncovered when wearing PPE should be carefully covered (wearing water resistant caps) or cleaned and/or disinfected afterwards (shoes, hair). An intact skin serves as a proper barrier against the SARS-CoV-2 virus, but can also serve as a vector for transmission. Hence, hygiene of DHCWs other than their hands is also required.