Coronavirus disease 2019 (COVID-19) is caused by severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2). SARS-CoV-2, which belongs to the family Coronaviridae of the genus Betacoronavirus was first reported in Wuhan, China, in December 2019.
SARS-CoV-2 is extremely infectious and is transmitted through infected human droplets while coughing, sneezing, or even while speaking. As of August 20, 2021, SARS-CoV-2 has infected more than 211 million worldwide and killed more than 4.4 million.
To study: In vitro studies evaluating the effectiveness of mouthwashes in Sars-Cov-2: a systematic review. Image credit: sum2020 / Shutterstock.com
Background
Epithelial cells of the oral mucosa have been reported to have high expression of the angiotensin 2 converting enzyme (ACE2) receptor. The SARS-CoV-2 spike (S) protein binds to ACE2 to infect the host cell.
Recently, scientists have found that the saliva of patients infected with COVID-19 contains a high viral load in the first week after the onset of symptoms. Even in asymptomatic patients, the presence of a high viral load in the oropharynx has also been observed.
These studies, therefore, indicate the role of the oral cavity in the spread of SARS-CoV-2. For these reasons, dental professionals are extremely vulnerable to COVID-19 infection as a result of the form of treatment that requires them to be close to patients.
Many mouthwash products have antiviral properties. Several organizations, such as the American Center for Disease Control and Prevention, have proposed the use of these mouthwashes before a dental procedure in order to reduce the spread of SARS-CoV-2.
About the study
A new study published in Journal of Infection and Public Health aims to evaluate the current body of publications in vitro research related to the effectiveness of mouthwashes in preventing the transmission of SARS-CoV-2.
To this end, the researchers retrieved a total of 162 titles, of which thirteen had a full-text review. However, only eight were included in this study.
This systematic review revealed the efficacy of the molecules in different oral groups of SARS-VOC-2. Among the mouthwashes tested, mouthwash containing Povidone Iodine (PVP-I) was reported to be the most effective against SARS-CoV-2.
Image credit: New Africa / Shutterstock.com
Active ingredients for mouthwash and COVID-19
PVP-I
PVP-I is a bactericidal and virucidal agent that is effective against several members of beta-coronavirus such as SARS-CoV and Middle East Respiratory Syndrome (MERS-CoV) coronavirus. PVP-I affects the nucleic acid structures of these viruses and alters surface proteins to eventually block viral binding to cells.
The studies considered in this review provided solid evidence that PVP-I can inactivate SARS-CoV-2, even after brief contact for 15 seconds and at low concentrations. This review also highlighted the cytotoxic effects associated with PVP-I. To this end, PVP-I appears to be toxic to the oral and nasal mucosa at a concentration greater than 2.5% and 5%, respectively.
Although commercial mouthwashes containing PVP-I do not reach the above concentrations, this is one of the most important parameters to be evaluated as new formulations are developed. It is important to note that pregnant women and people allergic to iodine should dodge their mouth with PVP-I. In addition, people with underlying thyroid disease or those receiving iodine radioactive therapy should refrain from rinsing their mouths with PVP-I.
Ethanol
The current study also found that SARS-CoV-2 is highly sensitive to a high concentration of ethanol (60% -70%), which is commonly used for surface decontamination. This concentration of ethanol is commonly used as a result of its ability to interfere with the lipid envelope, which subsequently leads to inactivation of the virus.
Some commercially available mouthwashes contain a very low concentration of ethanol. Several studies have shown that the combination of a low concentration of ethanol and essential oils is effective against wrapped viruses.
Ammonium compounds
Other bioactive components used in mouthwashes are quaternary ammonium compounds such as dequalinium chloride and benzalkonium chloride. These active components were also evaluated to determine their efficacy in reducing the SARS-CoV-2 viral load in the oral cavity. However, the mechanism behind its antiviral activity has not been documented.
Hydrogen peroxide
Many researchers have also studied the effectiveness of hydrogen peroxide (H2O2) in reducing viral loads. This component was found to effectively inactivate viruses such as influenza A and B viruses, adenoviruses, and rhinoviruses.
H2O2 damages the nucleic acid of the virus and increases the permeability of the cell membrane. However, previous studies revealed that H2O2 viral headlines could not be significantly reduced. Another reason why H2O2 it is not an ideal component of mouthwashes, it is that it is more cytotoxic than PVP-I, even after diluting it.
Chlorhexidine
Another common active ingredient in mouthwashes is chlorhexidine (CHX), which has bactericidal and bacteriostatic properties. This active ingredient is effective against surrounded viruses, such as herpesvirus 1, influenza A, and cytomegalovirus.
Conclusion
One of the limitations of the current study is that various methodological aspects and comparison groups varied between studies. However, the authors indicated that all evidence of in vitro studies show that PVP-I has a higher antiviral activity compared to other commonly used molecules.
The researchers stressed that more clinical studies need to be conducted to validate the effectiveness of the active ingredients present in mouthwashes discussed in this review.