highly significantP < 0.001
UVA alone, RF alone, and the combination of RF and consecutive UVA irradiation show a highly significant trend toward reduced cell viability (all P < 0.001). β-Coefficients for UVA irradiation, RF concentration, and their interaction term are −29.3% per mW/cm 2 UVA, −605.2% per % RF, and −1206.9% per mW/cm 2 UVA * % RF, respectively.