Importance of oral health in the origin and transmission of COVID-19

The oral cavity is not only one of the gateways for the entry and transmission of SARS-Cov-2, but some common periodontal diseases (such as periodontitis) can also aggravate the consequences of COVID-19.

The three main routes of virus entry appear to be the nose, mouth, and eyes, through their mucous membranes. It is now known that the infectivity of SARS-CoV-2 depends on its ability to penetrate cells, using angiotensin-2 converting enzyme (ACE-2) as the primary receptor and gateway for this virus to enter the cell. Since the epithelial cells in different mucosa of the oral cavity show a high expression of ACE-2, and given that the oral cavity is one of the first interfaces between the exterior and the organism, it is considered that there is a high potential for this pathway of colonization and viral infection to be determinant for the appearance of COVID-19.

In the mouth, studies show a relevant expression of ACE2 receptors in oral mucosa, especially in the tongue; moreover, the salivary glands have a word of these receptors even higher than that of the pulmonary mucosa. Therefore, the mouth is a suitable site for receiving SARS-CoV-2 and maintaining and transmitting it to others. Furthermore, there is now indirect evidence pointing to the idea that poor oral health could overexpress in the oral mucosa the ECA-2 receptors through which the virus enters our cells. 

Optimal oral hygiene and/or using certain mouthwashes with virucidal activity could reduce the risk of transmission and the severity of COVID. As oral health is essential for good general health, preventing diseases such as periodontitis or treating them appropriately is crucial, especially in the current coronavirus pandemic.

Clearly, poorer oral health, specifically in the gums (with periodontitis), favors more significant chronic systemic inflammation and a higher risk of suffering cardiovascular disease or diabetes, among other inflammatory-based pathologies. Therefore, this more significant systemic inflammation could make patients with periodontitis susceptible to a more severe COVID-19. In addition, there are indirect effects of COVID-19, derived from situations such as confinement or different restrictions, which clearly affect oral health through multiple mechanisms.

Given this situation, DENTAL-OFFICE.ORG points out that improvements in periodontal health and oral hygiene may help to control the COVID-19 pandemic. The impact of oral interventions on the levels of SARS-CoV-2 in the mouth can be very relevant, and the possible role of mouthwashes with virucidal action is particularly suggestive.

Since the beginning of the pandemic, and already in the dental clinics in Wuhan, it was recommended that patients, before any dental procedure, rinse with mouthwashes containing antiseptics capable of reducing the SARS-CoV-2 load in aerosols to reduce the risk of virus transmission. Subsequently, it has been shown that the virus could be present in relevant quantities in different mucous membranes of the mouth and salivary glands, especially in the first days of infection, due to the elevated expression of ACE-2 receptors; this could favor transmission by infected individuals. Finally, it has also been observed that people with a higher viral load in the mouth present greater severity of COVID-19.

Another aspect that stands out is the exemplary behavior of the dental clinics during the pandemic, first reducing the activity to what was essential during the confinement (exclusively emergency care) and then resuming the action when the safety measures made it possible, following the strict protocols, and carrying out the appropriate training for all the personnel. Studies show that, with these protocols, the dental clinic is a very safe place, mainly because the usual cross-infection control measures in the dental clinic were already very effective before this pandemic.

In the case of cross-infection (i.e., the reciprocal transmission of pathogens between patients and healthcare personnel in the clinical setting), this type of event has been minimal reporting in dental clinics. Instead, dentists have asserted their in-depth knowledge of cross-infection prevention by adapting to working at biosafety level 3 and professionally managing transmission barriers using effective disinfection technologies, all of which have reduced transmission in the high-risk environment inherent to this profession.