UV-C in Healthcare: Reducing the risk of Covid-19 infection in Dental Offices
Throughout the world, the global crisis caused by the spread of SARS-CoV-2 Coronavirus has brought all dental activities outside the emergency sector to a standstill.
It is now a question of drawing up and implementing protocols that protect doctors and medical staff and prevent cross-contamination and consequent infection of patients once they are allowed to reopen practices. We do not think it is helpful to focus here on the general and consensual measures in the waiting room (social distancing, limiting the number of patients, wearing masks, avoiding shaking hands…) and to protect the staff (frequent hand washing/disinfection, FFP2/FFP3 masks and face protection during clinical procedures…).
Instead, we would like to highlight two points that are rarely mentioned in the protocols currently in circulation. The most straightforward way to significantly reduce the risk of cross-contamination, as taught in all good dental schools, is to increase the average time of treatment: if this average time is doubled, the risk of cross-contamination of patients and dental staff is halved. At the same time, the negative financial impact of time-consuming cleaning/disinfection procedures is halved.
The second point concerns dental aerosols. On the one hand, SARS-CoV-2 is a respiratory virus that is very different from the viruses we are used to dealing with, such as HIV, hepatitis B, and C. This means the virus does not need to enter a wound for cross-contamination; simple airborne transmission is possible, as with viruses that cause colds (rhinopharyngitis) or the flu. But with potentially much more severe consequences.For the German Hospital Hygiene Association, coughing, singing, or simply talking are the primary sources of virus spread. This suspicion is confirmed by a letter from the American National Academy of Science to the White House. This letter suggests that Coronavirus could remain in the mist formed during breathing.
Furthermore, soil contaminated by patients in Chinese hospitals could be the source of new aerosols due to cleaning or staff relocation. An article in the New England Journal of Medicine (March 2020) found that the virus was viable for several hours in experimental aerosols. The same paper describes the survival of the virus for up to 3 days on metal surfaces like metal or plastic. Since a high proportion of patients who are positive for SARS-CoV-2 will be symptom-free or with very mild effects, symptomatic patients are infectious a few days before the onset of symptoms and possibly long enough after symptoms have subsided, all patients should be considered potentially infectious. For this reason, the use of masks in the waiting room is recommended for patients and secretarial staff.
Once dental treatment begins, the mask is removed, and the patient may become the source of a cloud of microdroplets. In addition, dentistry is characterized by the generation of very powerful aerosols through ultrasonic scalers, air/water spraying, air/water cooled, or air/water-cooled rotary instruments. The resulting cloud of microdroplets is contaminated with microflora from the patient’s mouth and upper airways. This is an extraordinary situation: Not only does the patient not wear a mask and has a wide open mouth, but his oropharyngeal microflora is strongly scattered outwards by some dental treatments.
It has been shown (Micik et al., 1969; Graetz C et al., 2014) that dental aerosols produce splashes with particles > 50 µm, which exhibit behavior that can be described as “ballistic” and directly contaminate the surfaces facing the patient (equipment carrier, floor) over a distance of 0.5 to 2 meters.
However, dental aerosols also produce a cloud of micro-droplets < 1 µm, which remain suspended in the air and may penetrate directly into the lungs. This microdroplet cloud is highly contaminated with oropharyngeal microflora (Dutil et al., 2009; Hallier et al., 2010; Kobza et al., 2018), and recent studies have shown that SARS-CoV-2 can remain viable for up to 3 hours in comparable aerosols (van Doremalen et al., 2020).
Recent work on these microdroplet clouds shows that they remain suspended for long periods and can spread over long distances. For dental practices, this means that after generating an aerosol in a Coronavirus-positive patient (often not symptomatic, see above), the ambient air can be potentially infectious for staff and the next patient.
This micro-droplet cloud will gradually settle on all surfaces in the dental office, including the floor. To reduce the risk of cross-contamination, significant measures should therefore be taken to decontaminate the atmosphere and all surfaces before treating the next patient such as reducing the risk of cross-contamination by aerosols and reducing aerosol formation/contamination during treatment.
Aerosols are only produced during treatments with ultrasonic scalers, air/water spraying, or air/water-cooled rotating instruments. For example, manual scaling/root gouging, tooth extraction, and implant placement are less at risk. It has been shown (Kampf et al., 2020) that hydrogen peroxide (H2O2) at 0.5% for 1 minute effectively kills the virus, as does povidone-iodine. A mouth rinse with 1% H2O2 or betadine can therefore be recommended before dental work begins. Note that chlorhexidine has a negligible or no effect on Coronavirus!
High performance vacuuming during aerosol generation processes can significantly reduce (up to 90%) the power of aerosols but not eliminate them. Caution: Check where the aspirated air is discharged (see below). The use of a rubber dam, when clinically indicated, can increase the strength of the aerosol but reduce microbial contamination. Reduction of air pollution. There are various methods of continuous air disinfection/cleaning:
Ventilation systems with HEPA filters effectively reduce the virucidal load in the air (SARS-CoV-2 has a size of 0.1 µm, but since micro-droplets carry it, it is effectively stopped by HEPA filters with a pore diameter of 0.3 µm). However, the filters themselves can be highly infectious. Ventilation systems that combine filters (ideally HEPA filters) with UV disinfection of the filtered air appear to be most effective at decontaminating the atmosphere. Several articles (see below) have shown that UV in sufficient doses effectively destroys the RNA of viruses, including Coronaviruses.
UV-FAN Air and Surface Disinfection
Note 1: Ventilation systems have no immediate effect and require some time to decontaminate.
All air in a room (15 to 30 minutes) after the last aerosol production, which varies according to the flow rate (m3/h) of the device and the volume of the room (the time required is always longer than the simple calculation of the room volume/flow rate of the device, as clean air is reinjected into the room and mixes with unclean air)
Note 2: No ventilation system can decontaminate surfaces (lighting system, surgical unit, radio, equipment rack, instrument whips…) and the floor!
Decontaminating surfaces/floors with hydrogen peroxide + colloidal silver spray (Nocospray) can be effective at disinfecting surfaces, but it does not decontaminate the air and it cannot be used in connection with air purification systems by ventilation + filter/UV; if the diffusion time is only 3 minutes, the contact time required is 30 minutes per day for cleaning and > 60 minutes for curative treatment (i.e., after the last aerosol)! The staff cannot stay in the room.
Therefore, this system is not easily integrated into a routine protocol to reduce cross-contamination of Covid-19. Manual cleaning and disinfection of all surfaces A strict checklist must be used to ensure that no surface is overlooked. This procedure takes a long time (at least 10 to 15 minutes) and consumes a lot of time. However, it can be carried out while the ventilation and decontamination systems operate. Floors are contaminated with aerosols, and it was suspected that staff movement could stir up infectious particles in the air. They are now rarely (ever?) cleaned between patients.
Since SARS-CoV-2 is sensitive to soap, detergents, ethanol, and aldehydes, the most commonly used surface disinfectants will be effective. The instructions for the use of the product must be followed. The only method for decontaminating or sterilizing air and surfaces (including soil) is direct exposure to UV light. There is ample evidence that UV irradiation is effective at denaturing Coronavirus RNA. This is the method of choice, if available, for the disinfection of hospital rooms according to Covid patients and public transport. It can be combined with continuously ventilated decontamination systems. Unfortunately, our market research has not yet identified any UV sterilization systems that are well-suited for dental practices (the presence of central dental chairs requires at least two UV lamps on each side or a mobile UV unit), except for some UV robots at a very high price.
Suppose UV devices designed for dental practices are available at an affordable price. In that case, they could become the benchmark for the fastest (5-10 minutes) complete decontamination (air/surface/floor) of the operating room after aerosol formation.
Practitioners should check whether their air compressor is pumping fresh air from outside or room air. In the latter case, a HEPA filter should be fitted to the compressor to prevent contaminated air from entering the dental office. The air sucked in by the high-speed suction system to reduce the spread of potentially infectious aerosols is then discharged by the suction machine elsewhere. Practitioners should, therefore, carefully consider the design of their system.
If the air inside the building is blown out, an air decontamination system (UV ventilation) must be installed in the room where the air is blown out, or a HEPA filter must be attached to the air outlet hose. HVAC (reversible air conditioning) systems: Clinicians should check how the building ventilation system has been set up, as it is known (Li et al., 2007) that micro-droplets of aerosols can be transported through ventilation systems. This is fine if the air is sucked in (negative pressure) and expelled to the outside. When positive pressure is applied, air is typically expelled from the dental office into standard rooms.
Dental aerosols can be distributed in practice in this way.Practice architecture can lead to very difficult or even impossible problems. If the individual dental offices are not physically separated, for instance, infectious bacteria aerosols can spread from one dental chair to another. This is sometimes the case in modern dentistry practices, where solutions can be found on a case-by-case basis. This is even more common in dental clinics or hospitals, where several dental chairs are sometimes grouped in large spaces. Controlling the flow of microdroplet clouds seems impossible in these open areas.
As dental treatment continues, large open spaces should be discussed or questioned during the current Covid 19 pandemic.
Ultraviolet rays are electromagnetic waves that are part of the electromagnetic spectrum. Electromagnetic waves are divided into three main wavelength bands, expressed in nanometers, nm: Ultraviolet rays (UV) 100-400 nm Visible rays (light) 400-700 nm Infrared rays (IR) 700-800,000 nm UV rays are in turn, identified in three bands:
- UV-A (315-400 nm) with tanning properties;
- UV-B (280-315 nm) con proprietà terapeutiche e di sintesi della vitamina “D”;
- UV-C (100-280 nm) with germicidal properties.
UV rays are eco-friendly. Bacteria, viruses, spores, fungi, molds, and mites are all sensitive to UV-C rays and can be eliminated by them. Microbes cannot acquire resistance to UV-C rays, which only occurs using chemical disinfectants and antibiotics. When using ordinary disinfectants, environmental pollution is inevitable.
They also carry severe risks from the direct inhalation of vapors or the ingestion of foods contaminated after coming into direct contact with chemical disinfectants. Where the use of chemical disinfectants is unavoidable (food/pharmaceutical/healthcare industries, etc.), using ultraviolet rays in the disinfection process can reduce the amount needed, which allows for significant cost savings and is better for the environment while maintaining – and most of the time, improving – disinfection quality.
UV-C ray devices can be installed in most environments and machinery.
They can be programmed to maintain the same level of disinfection day and night, ensuring ideal hygiene conditions without any fluctuation in quality. In contrast, chemical disinfectants are most effective at the time of use.
LIGHT PROGRESS UV-C-equipped devices offer low running costs and are maintenance-free, besides standard bulb replacement. These robust and highly durable systems provide exceptional value for money. For this reason, eliminating germs using UV-C as opposed to (or together with) other systems offers excellent results at a low cost.
UV-C rays (100-280 nm) have a robust germicidal effect and reach their maximum efficacy at the 265 nm wavelength. The germicidal effect of UV-C radiation covers bacteria, viruses, spores, fungi, molds, and mites; this is mainly due to the destructive impact of the UV-C rays on their DNA, which damages their reproductive system and prevents them from replicating.
These lamps have an emission of around 90% over the 253.7 nm wavelength. This frequency is invisible to the human eye and has solid germicidal power. The remaining 10% of the lamp’s emission is visible (typically appearing as a blueish light).
Yes, UV-C rays are found in nature as they are generated by the sun, but the ozone layer in the atmosphere acts as a shield that stops them from reaching the earth’s surface.
Legal limits for microbiological contamination of drinking water are very stringent under Legislative Decree 31/2011. Water can be treated chemically by chlorination or physically by UV-C rays and heat to eliminate microorganisms. Initially, ingested water may contain dangerous residual contaminants derived from chlorine, such as chloramines, which alter the taste and smell of water, or by-products harmful to human health and the environment, such as inorganic substances, which contribute to trihalomethane, which is highly carcinogenic. It may be possible to avoid the problems mentioned above by heating the water before use, but it is not practical and would require long cooling times to solve.
By irradiating microorganisms with a much higher dose than the minimum safety dose, a UV-C ray device installed on the pipe near the point of use of the water can safely eliminate all microorganisms. Systems and spare parts (lamps) are very inexpensive to buy and maintain. When chlorine and derivatives are present, UV-C rays reduce them to elementary particles that are harmless to humans.
When you turn on a UV-C lamp you get a strong reduction in the microbes present in the ambient air and on the surfaces reached by the UV rays. The device reduces Bacillus, Coli, Clostridium, Legionella, Vibrio, Salmonella, Listeria, Pseudomonas, Staphylococcus, Streptococcus Bacteria by 99% in a matter of minutes if placed three meters from it. This feature also allows you to intervene in areas otherwise unreachable by solid bodies such as objects and cleaning and disinfectant products. Although chemical disinfectants are mandatory, irradiating surfaces avoids shaded areas, does not generate resistant species and can be used day or night (in the absence of people), preventing rapid recontamination of surfaces and ensuring that they are always in optimal microbiological condition.
UV-C rays are used every day, primarily in:
Food and pharmaceutical industries disinfect the air and surfaces of production environments and disinfect product containers (packaging), to isolate “protected” areas for the production and packaging of products, such as clean rooms, from areas at risk of contamination. These actions significantly increase the safety and shelf life of the products we buy, with numerous benefits to our health given that they do not leave any residue and allow the elimination or reduction of chemical disinfectants, which on the contrary, may leave hazardous residue on the products.
Hospitals, to avoid the transmission, and therefore contagion of dangerous bacteria or viruses that may be found in their air or transmitted by contact between the sick and visitors.
Water treatment systems provide drinking water for humans and animals and for healthcare use to eliminate all microorganisms that might be found in water from wells, tanks, and aqueducts. This system is mandatory downstream of a carbon-activated filter, for example, in water dispensers, which are becoming increasingly popular in cities.
There are no limits to the possible applications of UV-C light; even in domestic environments, it is used to prevent mold formation on walls, eliminate mites from the bedroom, keep the indoor air healthy, and treat water.
UV-C light can also eliminate odors and grease deposits in industrial kitchens and restaurants, assisted by ozone emission. Light Progress has developed a specific system also for this type of application.
Bacteria, viruses, spores, fungi, molds, and mites are all sensitive to and eliminated by UV-C radiation.
Each bacterium, virus, yeast, mold, or mite requires a different UV-C dose to be deactivated or eliminated. There are widely recognized documents that report these levels. Light Progress has one of these documents and uses it regularly in designing and implementing its systems. To give an approximate idea regarding the application times of UV-C rays, these can range from fractions of a second to several seconds.
Viruses, bacteria, mold, animal waste, mites, and pollen are among the leading causes of dangerous infections and allergies. Each contaminant is dispersed differently: mites, spores, bacteria, and mold, for example, are continuously transported by air, while other bacteria and viruses are “grouped” into solid particles, such as spores or drops of moisture, and then inhaled by humans.
In air conditioning systems, when contaminants get inside the air treatment unit (ATU) and air distribution ducts, the design, which is dark and moist, becomes a breeding ground for them to grow and multiply, making the air we breathe unsafe.
The air also contains concentrations of dangerous chemical pollutants if inhaled in large quantities or continuously. Irradiating air in a central system or installing an air purifier complete with UV-C lamps and a TiOx titanium dioxide filter dramatically reduces the likelihood that these pollutants (whether microbiological or physicochemical) will result in health problems that often can only be diagnosed after many years.
The efficacy of disinfection systems can easily be ascertained through microbiological analyses or simple swab tests used to identify the presence of microorganisms on the tested surfaces. To verify the same microbial load on surfaces, in the air, and in water, before and after the treatment, it is necessary to carry out lab tests such as those for HACCP. For chemical disinfectants, producers need to provide tests declaring their disinfectant capacity; Light Progress has similarly carried out necessary tests in university labs and at private accredited bodies. Of course, for chemical disinfectants and UVGI technology to obtain the same laboratory results, the products must comply with the instructions for use.
UV-C rays cannot penetrate solid bodies, unlike ionizing radiation such as x-rays and gamma rays, which are highly dangerous to humans, even at low doses. To eliminate microorganisms using UV-C rays, they must be present on the surface of an object or transported by the air.
ARE THERE ANY MATERIALS THAT CAN BE PENETRATED BY UV-C RAYS?
Significantly few materials will not block the passage of the germicidal wavelength (253.7 nm, invisible), including quartz and certain plastics such as PE or tetrafluoro-derivatives, but only if these are just a few microbes thick.
Regular window glass, polycarbonate, and other transparent materials through which it is possible to see the bluish light of UV-C lights completely nullify their germicidal effect, acting as a screen.
WHAT EFFECT DO UV-C RAYS HAVE ON THE HUMAN BODY?
Continuous irradiation of the eyes and skin could cause erythema and conjunctivitis, which generally clear up in a few hours. In any case, it is sensible to avoid direct, close-up exposure to sources of UV-C rays, even for short periods. To prevent direct exposure, cover the area to be protected using any material that is not transparent to visible light (cotton or woolen clothing or overalls) or glass or transparent plastics (masks, helmets, glasses, etc.).
ARE THERE ANY WAYS TO PROTECT AGAINST FALLING FRAGMENTS FROM THE UV-C LAMP?
Yes. Light Progress offers two solutions in a unique plastic material: Uvlon Frame and Uvlon Pipe. Uvlon Frame is made from a film attached to the device and collects fragments from breakage. Uvlon Pipe is a casing thermally applied to the UV-C tube in the factory, which increases its mechanical strength (car windscreen effect) and collects and retains any broken fragments inside.
WHAT EFFECT DO UV-C RAYS HAVE ON PLASTIC SURFACES?
UV-C rays are similar to solar rays but do not transmit heat. However, like solar rays, they tend to have a yellowing effect on plastics exposed for extended periods (mainly white plastics).
Bacteria, Viruses, Spores, Fungi, Mold, and Mites are all sensitive to, and can therefore be eliminated with, UV-C light. Microbes cannot acquire resistance to UV-C light, unlike that which occurs using chemical disinfectants and antibiotics. UV rays are ecological. Polluting the environment is inevitable using normal disinfectants. Directly inhaling the vapors, or swallowing food products contaminated by any contact with said chemical disinfectants, can also give rise to a number of serious risks. In cases where chemical disinfectants cannot be eliminated (food, pharmaceutical, healthcare industries, etc.), using ultraviolet rays for disinfection allows a reduction in their use, with considerable economic savings and greater care for the environment, while maintaining and almost always improving the level of disinfection. UV-C light devices can be installed in environments and on machinery and be programmed to maintain the same level of disinfection day and night, guaranteeing ideal hygiene conditions, without highs and lows. On the contrary, chemical disinfectants are effective only during their actual use. Using LIGHT PROGRESS equipped luminaires, operating costs are negligible; it could be said that “LIGHT PROGRESS” UV-C systems do not require maintenance except for the normal replacement of the lamps. The cost/benefit ratio is considered excellent; the devices are both powerful and long-lasting. Hence the elimination of germs using UV-C technology is low-cost and highly effective compared to (or in combination with) other systems.
UV-C light genuinely works if properly applied and with the necessary precautions. The difference between a quality project, and an application that fails to bring the desired results, lies in the degree of knowledge about the subject, and level of experience acquired over time. Light Progress has been developing successful projects worldwide since 1987, and has built a client portfolio consisting of important companies in all fields requiring certified hygienic conditions to produce quality products and services.