2021, Number 2
Use of UV light in dentistry as a disinfectant method against SARS-CoV-2
Full text
Language: English/Spanish [Versión en español]
References: 43
Page: 145-153
PDF size: 172.84 Kb.
ABSTRACT
The following literature review will refer the beginnings of UV light application in dental practice as well as its development in different dental procedure areas. Due to the rapid spreading of current COVID-19 pandemic in different countries, new technologies are being sought to help control the SARS-CoV-2 virus spreading. One of them, ultraviolet light, is being considered as a safe and effective disinfectant option; recent studies suggest so. UV radiation is a disinfectant method for the inactivation of pathogenic microorganisms, including human and animal viruses.INTRODUCTION
Ultraviolet light has had several applications in food industry and in medical, pharmaceutical and dental areas. There is a boom of this alternative disinfectant method marketed in developed countries, since it is not harmful to the human body. Furthermore, it eliminates needs of transporting, storing, and handling hazardous chemicals and provides effective disinfection without creating troublesome by-products.1,2
UV light has proven effectiveness on several elements. It has been used from 200 to 280 nm wavelength to treatment the food surface, modifying the flora potentially pathogenic for humans. For this reason, UV light has been used in water purification for human consumption, in meat products and in deactivation of enzymes that modify the quality of the fruits and vegetables nutritional content. Likewise, UV light produces oxidative processes that allow the destruction or separation of cellular elements that contain transmissible genetic material, thus slowing down gene mutation processes, and allowing pathogens and other microorganisms' reduction.3,4
ULTRAVIOLET LIGHT OVERVIEW
Ultraviolet light is a part of the electromagnetic spectrum, with wavelengths between 100 and 400 nanometers (nm). The shorter the wavelength, the greater the energy produced. The biggest source of UV radiation comes from the sun. However, there are artificial lighting sources such as lamps or flashlights.5 The most common sources are commercially available low and medium pressure mercury arc lamps (Figure 1).1,6
A typical mercury arc lamp consists of a quartz or vitreous silica tube, both UV transmitters, hermetically sealed and with electrodes at both ends. UV light is produced as a result of current flow through mercury vapor between the lamp electrodes. The main difference between germicidal and fluorescent lamp is that the first one is made with quartz, while fluorescent lamp uses glass, with an internal phosphor layer that becomes UV light into visible light (Figure 2).1,6
UV LIGHT USES IN RESTORATIVE AND COSMETIC DENTISTRY
It has been more than 30 years since the photo cured system for dental resins was introduced to the market. In the 1970s, the first type of light source used in stomatology for photo activation were UV light lamps, although they were quickly replaced by halogen lamps in the mid-1980s.7,8
Fluorescence is a resin feature, produced by the absorption of light by an object and the subsequent spontaneous emission of light of a longer wavelength than that absorbed, this allows a resin to be closer to the natural color and brightness of a tooth. Ultraviolet light can make it easier for the dentist to completely remove resin and preserve healthy tooth tissue.9,10
UV rays in the tooth structure allow to observe that fluorescence intensity in dentin is much greater than that produced in enamel. This light is useful to show the tooth fluorescent properties and to differentiate aesthetic tooth restorations and fractures or porosities of ceramic restorations.5,10 Dental fluorescence has also been successfully used to detect carious lesions on flat tooth surfaces thanks to the organic components of the tooth structure and the marked difference in fluorescence between normal and carious enamel.11
DENTAL IMPRESSIONS DISINFECTION
The COVID-19 pandemic reminds to dentists and health professionals to follow an adequate biosecurity protocol, since in practice they are exposed to a wide diversity of microorganisms: spores, fungi, protozoa, bacteria and viruses such as SARS-CoV-2.12 Prosthodontists are at additional risk of contagion due to the spread of infections through contaminated laboratory equipment. Various materials are daily used to obtain models of dental arches, which upon contact with the patients' mouth are contaminated with blood and saliva. The main potential route of transmission from a patient to dental technician is through contaminated impressions and dentures.13
Procedures in stomatology involve face-to-face communication with patients and frequent exposure to saliva, blood, body fluids, and the handling of sharp instruments. Saliva is a virus transmission vehicle and respiratory viruses could be transmitted directly or indirectly through saliva, which is particularly important.14 Sabino-Silva et al in 2020 determined that there is a need to increase research to detect SARS-CoV-2 in oral fluids and its impact on the transmission, as it is crucial to improve prevention strategies, especially for stomatologists and health professionals.15 Saliva could play a critical role in person-to-person transmission.16,17
The American Dental Association (ADA) recommends disinfection of dental impressions immediately after removal from the patient's mouth to prevent cross-infection between patients and dental staff.18 On March 15, 2020, the New York Times published an article where a schematic figure describes that dentists are the workers most at risk of being affected by SARS-CoV-2, much more than nurses and general practitioners.17
The COVID-19 pandemic has raised the level of infection control in dentistry. Permanent adjustments and improvements have been made as part of a security strategy for all those involved, the users and direct and indirect providers of dental services.12
Some chemical solutions commonly used to disinfect impressions could cause significant dimensional changes. The impression accurate is an important attribute that determines the success or failure of the restoration or prosthesis. In 2014 Godbole et al. conducted an in vitro study on 40 samples with polyvinylsiloxane. UV light was applied to 20 of them for 10 minutes at 10 cm distance and 254 nm wavelength; no disinfectant method was applied to the rest. The samples were taken from a master model in order to establish a control of the measurements obtained and to observe if they presented any significant dimensional difference. They concluded that UV light was a safe and acceptable option for disinfection as well as not significantly affecting dimensional stability.13,18
In 2019 Nimonkar et al conducted a comparative study with chemical disinfectants and UV light. Four groups were made: 10 samples were disinfected with 2% glutaraldehyde, 10 samples with 1% hypochlorite, UV light was applied to 10 of them at 10 cm distance and 254 wavelengths. The process in these three groups lasted 20 minutes. The fourth group was the control group. The results showed that UV light did not cause significant dimensional changes in the polyvinylsiloxane impressions when compared to the results shown by chemical disinfectants. UV light as a disinfectant could be especially beneficial for hydrophilic materials such as polyethers, alginate, and agar.18,19
DENTAL EQUIPMENT DISINFECTION USING ULTRAVIOLET LIGHT AND ITS EFFECTIVENESS IN DEALING WITH THE SARS-
The COVID-19 pandemic has transformed health services worldwide, forcing to find effective techniques for care areas disinfection. Disinfection term refers to reduction of the pathogens concentration to non-infectious levels. Dentists are the professionals with the highest risk of transmission of COVID-19 since from diagnosis to treatment, the dentist and the patient are face to face, in addition to the production of aerosols during dental procedures. Pathogenic microorganisms could be transmitted through inhalation of airborne that can remain suspended in the air for long periods. They could also be transmitted by direct contact with blood, oral fluids or other patient materials, contact of conjunctival, nasal or oral mucosa with droplets and aerosols containing the microorganisms of an infected individual and propelled a short distance by coughing and talking without a mask. A further form of transmission is indirect contact with contaminated instruments and environmental surfaces.16
Technological advances are being developed every day that enter the market, which is why the concern arises to apply them in dental practice. Such is the case of the ultraviolet light lamp as a disinfectant. The main target of ultraviolet light disinfection is genetic material-nucleic acid. The absorption of ultraviolet light by nucleic acid causes a rearrangement of genetic information, which interferes with the cell reproductive ability. Consequently, the microorganisms are inactivated. A cell that cannot reproduce is considered dead or inactivated.6,20
Ultraviolet light is classified according to its wavelength; the range between 200-280 nm (UV-C) is considered germicidal. The main problem in using UV light is the shadow effect from different structures located in the area to be sterilized. However, due to the need for disinfection currently on the market there are portable ultraviolet light systems and even autonomous robots for the disinfection of hard-to-reach areas.3,6
COVID-19, caused by the severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is a highly infectious disease21 with an incubation time of up to 14 days.22 SARS-CoV-2 is transmitted through droplets or aerosols secreted by an infected person.23 It can also spread through surfaces contaminated with nasal, oral and ocular mucosa.24 It can stay on surfaces for up to 72 h25 and can travel in the air up to 8 m.26
It has been suggested that UV light can decrease COVID-19 and other human coronavirus strains, such as SARS and MERS. It is estimated that natural UV light can inactivate 90% of SARS-CoV-2.27 UV radiation is a natural environmental antimicrobial and previous studies have shown that climatic variables such as temperature, sunlight, or ultraviolet light can affect the transmission of influenza and other viruses. UV-C, a type of UV light, is a strong disinfectant that destroys genetic material, including viral particles and SARS-CoV-2.28
UV rays can inactivate SARS-CoV-2, as well as coronaviruses, including SARS-CoV-129 and MERS-CoV,30 as shown under laboratory conditions and in a certain dose range (200-280 nm).31 UV rays also help generate vitamin D in the body through skin exposure. Given the reported link between vitamin D and COVID-19, it is possible that UV rays help prevent COVID-19 through its generation of vitamin D and subsequent positive immune effects.32,33 To et al found that higher UV radiation is associated with lower transmission of COVID-19.34 These findings indicate the need for further research about the relationship between climatic factors and COVID-19 transmission.34,35
Gerchman et al in 2020 used the human coronavirus OC43 (HCoV-OC43) as a surrogate for SARS-CoV-2, to develop a dose-response curve with UV-LED light at different wavelengths. The UV exposure experiments were performed using C a UV-LED system (PearlBeam) from AquiSense technologies (Charlotte, NC, USA). The study showed that the sensitivity of the human coronavirus (HCoV-OC43) was wavelength dependent 267 nm ~ 279 nm > 286 nm > 297 nm. Other viruses showed similar results, suggesting that UV-LED with an emission peak at ~ 286 nm could be an effective tool in the fight against human coronaviruses.24
Coronaviridae are the largest enveloped RNA viruses.24 They can be differentiated into four genera: alpha, beta, delta, and gamma. Alpha and beta-type coronaviruses infect humans, primarily the respiratory systems, gastrointestinal and central nervous.14 Both HCoV-OC43 and SARS-CoV-2 belong to the genus Betacoronavirus, both types of coronavirus HCoV-OC43 and SARS-CoV-2 are very similar, so human coronavirus HCoV-OC43 as a substitute for SARS-CoV-2 and thanks to the results obtained with LED light it can be suggested that it is possible to be effective against SARS-CoV-2.24
Wilches et al suggests that despite the lack of consensus about the intensity that should be used to inactivate SARS-CoV-2, since human coronaviruses have a similar genomic structure, it is possible that far UV-C is also effective against SARS-CoV-2. Therefore, far UV-C appears to be a relatively safe and inexpensive tool for decontaminating aerosols and surfaces that can be a vehicle of spreading SARS-CoV-2 or other infectious agents.36
DISCUSSION
Dental profession entails a constant risk of contracting diseases from various pathogens such as the human immunodeficiency virus (HIV), herpes simplex virus, hepatitis B virus and Mycobacterium tuberculosis, mainly. Before the COVID-19 pandemic, most dentists did not perform an adequate protocol for infection control in their clinics. At present, different methods have been tried to minimize the risk of contagion, such as having the appropriate personal protective equipment, as well as the cleaning and disinfection of material, instruments and work areas.14,16,17,37
Ultraviolet light has had a remarkable and progressive development, it has been used in food industry and for water purification. It has recently been proposed due to the advantages of its use as a disinfectant method for dental equipment and material, since it reduces contact with infected material or instruments, therefore reducing the possibility of contagion, in addition to its efficacy and safety, low cost, practicality and easy handling.3,38-40
Since 1970 UV light has been used in dentistry for aesthetic procedures, such as teeth whitening, resin curing light,7,8,41 auxiliary for diagnosis and detection of caries, dental fissures, restoration fractures, thanks to the fluorescent properties not only of resins but also of dental tissues.5,9-11 In addition, the germicidal properties of ultraviolet light have been used as it has proven to be an effective disinfectant prior to the placement of titanium implants, reducing the appearance of peri-implantitis and allowing adequate osseointegration.42,43 It has also proven to be an effective disinfectant of impression materials such as polyvinylsiloxane compared to other chemical types, as it does not damage the properties and dimensional stability since it does not generate heat or require a certain temperature for its use.18,19 Even so, more research about ultraviolet light applications is lacking as it has not been given due importance, nor has it been the subject of frequent study despite the many benefits it offers.
CONCLUSIONS
Based on the research carried out, it can be concluded that the use of ultraviolet light is highly effective as a disinfectant for dental equipment, surgical instruments and impression materials, as well as surfaces in dental clinic. In addition, it is effective against some pathogens, including the influenza virus, and recent studies suggest that it might be effective against SARS-CoV-2, making it an excellent alternative for dental area in the current pandemic.
REFERENCES
Lobos-Lagos N. Estudio de la fluorescencia visible inducida por luz Ultravioleta en dientes anteriores, según edad en pacientes de la Clínica Odontológica de la Universidad de Chile [Tesis pregrado]. Santiago, Chile: Universidad de Chile; 2018. p. 52. Disponible en: http://repositorio.uchile.cl/handle/2250/148633
Ruz-Rojas MJ, Vega Bendaña YP. Eficacia de la luz ultravioleta como medio diagnostico auxiliar para la remoción de restauraciones de resina presentes en la estructura dental. Estudio in vitro. Universidad Americana [Tesis pregrado]. Managua, Nicaragua: Universidad Americana; 2011. p. 58. Disponible en: https://biblioteca.uam.edu.ni/repositorio/bitstream/handle/721007/1117/01204631.pdf?sequence=1&isAllowed=y
Rodríguez K. Eficacia en la desinfección de cepillos dentales con luz ultravioleta, gluconato de clorhexidina al 0.12% y agua destilada de niños de 5 a 12 años que asisten al área de odontopediatri?a de la clínica Odontológica Dr. Rene? Puig Bentz de la Universidad Nacional Pedro Henri?quez Urena, en el periodo mayo-agosto, 2018. Experimental, in vitro [Tesis]. Santo Domingo, República Dominicana: Universidad Nacional Pedro Henri?quez Urena; 2018. p. 64. Disponible en: https://repositorio.unphu.edu.do/handle/123456789/1136
AFFILIATIONS
1 Facultad de Odontología Unidad Saltillo. Universidad Autónoma de Coahuila, México.
2 Facultad de Ciencias Químicas. Universidad Autónoma de Coahuila, México.
CORRESPONDENCE
Alejandra Isabel Vargas Segura. E-mail: alejandravargas@uadec.edu.mxReceived: Marzo 2021. Accepted: Agosto 2021.