Background:
In order to reduce the transmission of pathogens between the dental office, dental laboratory and the patient, it is necessary to properly disinfect the denture. During the COVID-19 pandemic, it was recommended to disinfect dentures through exposure to UVC rays or with 1% hydrogen peroxide solution.

Aim of the study:
To assess the effect of both methods of disinfection on the mechanical strength of acrylic materials.

Material and methods:
Three materials: Villacryl H Plus (M1), Villacryl SP (M2) and Villacryl S (M3) were used to make ten samples of each material, which were then divided into two groups.The plates in the first group were soaked in a 1% hydrogen peroxide solution for 30 minutes, and then irradiated with UVC rays for 30 minutes. Samples from group 2 (control) were subjected to load tests without prior disinfection. Flexural strength was tested using the INSTRON 3345 in the three-point method. The obtained breaking forces [N], multiplied by the area of fracture, gave the result of bending stress [MPa], which was subjected to statistical analysis.

Results:
The greatest change was noted for Villacryl S (M3). The mean stress value decreased from 71MPa to 54MPa and was statistically significant (p=0.05). Similarly, Villacryl H Plus (M1) changed its properties to a statistically significant extent. The average stress value decreased from 56MPa to 42MPa (p=0.05). The smallest stress difference was noted for the Villacryl SP (M2) material (from 80MPa to 72MPa) and it was statistically insignificant.

Conclusions:
The use of two methods of disinfection affects the strength properties of dental acrylics.