SARS-CoV-2, which causes COVID-19, is classified by the World Health Organization as an airborne pathogen transmitted following exposure to infected droplets and aerosols. This virus is known to be present in saliva, the salivary glands, gingival crevicular fluid and in oral mucosal cells. Thus, the oral cavity can act as a reservoir and has been suggested as a route of transmission.
Patients infected with SARS-Cov-2 have been found to have a high viral load in their saliva with potential for transmission of the virus. The use of mouthrinses pre-procedurally has been suggested to reduce the salivary viral load.
It is known that the intra-oral bacterial load is reduced by mouth rinses containing chlorhexidine (CHX), hydrogen peroxide (HP), and cetylpyridinium chloride and zinc lactate (CPC + Zn), which are often used in oral care. However, there has been relatively little research on the effectiveness of mouthrinses on the salivary SARS-Cov-2 viral load.
A clinical trial has investigated the effects of different mouthrinses on salivary levels of SARS-CoV-2. Three commercially-available mouthwashes were investigated:
1. 0.075% CPC + Zn - rinsing with 20 mL for 30 seconds
2. 1.5% HP - rinsing with 10 mL for 1 min
3. 0.12% CHX, rinsing with 15 mL for 30 seconds
In addition, the effect of a combination of rinsing with 10 mL of 1.5% HP for 1 min, followed by rinsing with 15 mL of CHX for 30 seconds was evaluated. All mouthrinses were compared to rinsing with 20 mL of distilled water for 1 minute (the placebo).
Saliva was collected before rinsing, immediately after rinsing, 30 minutes after rinsing and 60 minutes after rinsing. Testing for the viral load was performed using qRT-PCR, an accurate method for analysis.
Findings were that 0.075% CPC + Zn mouthrinse and 0.12% CHX mouthrinse both significantly reduced viral loads of SARS-CoV-2 immediately after rinsing and was still significant at 60 minutes. Rinsing with the 1.5% HP mouthrinse also resulted in an immediate reduction in the viral load after rinsing, and was still significantly reduced at 30 minutes. The greatest decrease immediately after rinsing was obtained using the CPC+Zn mouthrinse. No additive benefit was obtained at any timepoint by sequentially rinsing with the HP and then the CHX mouthrinse.
It is suggested that they may help reduce the viral load by destroying the viral envelope needed for binding to cells in the oral cavity and/or by mechanically reducing the salivary viral load. The mechanism of action by which these products reduce the viral load in the oral cavity requires further investigation. These results are encouraging and warrant further investigation and suggest that these products could be considered as risk-mitigation strategies for patients infected with SARS-CoV-2.