Figure 5

(A) Analysis of hydroxyl radicals generated by UV-A irradiation of silver ion solution (2 mM) with (a): dispersion of S. mutans, (b): dispersion of A. actinomycetemcomitans, (c): biofilm of S. mutans, and (d): biofilm of A. actinomycetemcomitans. Hydroxyl radicals were qualitatively and quantitatively analysed using an electron spin resonance (ESR)-spin-trapping technique with DMPO as the spin trap agent. ○ and ▴ show the MnO marker and DMPO-OH, respectively. (B) Hydroxyl radicals generated by silver nitrate solution application and UV-A light irradiation for bacteria. Hydroxyl radicals were qualitatively and quantitatively analysed using the ESR-spin-trapping technique with DMPO. (a) The yield of DMPO-OH generated by silver nitrate solution application with UV-A light irradiation to S. mutans suspension (•), A. actinomycetemcomitans suspension (▴), ultrapure water(×), and without bacteria (◾). (b) The corresponding values for S. mutans biofilm (•), A. actinomycetemcomitans biofilm (▴), and ultrapure water without biofilm (◾). Values and error bars indicate the mean and standard deviation, respectively. Statistically significant differences are shown, p < 0.05 (*).