Effect of moisture on filtration effectiveness of dental face masks against pathogenic bacteria

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Hee-Jeong Ahn, Gyu-Sik Shim, Sung Hoon Kim, Sung-Hwan Bang, Hyo-Suk Song, Jang-Sik Ko, Yong-Seok Kim, Bo-Kyun Kim


Background/Objectives: This study aimed to compare the effectiveness of dental mask filters for pathogenic bacterial protection with and without the moisture for a proper standard for replacing dental masks.

Methods/Statistical analysis: A ventilator was attached to a manikin wearing a dental mask. An aerosol application 100 μl of bacterial inoculation solution cultured in a brain heart infusion (BHI) broth for one day was performed on the external surface of the mask, and a ventilator then attached without additional humidification. After four hours, both surfaces of the dental masks were sampled using sterile swabs.

Findings: One ml of the sample was dispensed on Petrifilm Staph Express plates, then grown for 24 hours at 37 degrees. The same process was used for an additional test, but with samples taken from both surfaces after eight hours.

In the test model with no humidification, no bacteria were found after four or eight hours on the inside surface of the mask. With humidification, no bacteria were found after two hours, but after four hours of ventilation bacteria were found on the inner surface.

Improvements/Applications: The use of dental masks for pathogenic bacterial filtration should not exceed four hours, and dental masks over two hours could be reused after being dried thoroughly.  


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