OBJECTIVETo investigate the effects of incorporating three different zinc oxide (ZnO) on the antibacterial activity of composite resin.

METHODSThe minimal inhibitory concentration (MIC) and minimal bactericidal concentration (MBC) of nano-ZnO, tetrapod-like zinc oxide whiskers (T-ZnOw), micro-ZnO against Streptococcus mutans were examined by the broth dilution test. Then the three different ZnO were added to the powder of one kind of bicomponent self-cured composite resin at 5% respectively, and the antibacterial activities of the resin specimens were evaluated using the membrane covering method before and after 3-month accelerating aging.

RESULTSThe MIC values of the three different ZnO against Streptococcus mutans were 78.13, 312.50 and 1 250.00 microg/mL respectively and the MBC values were 156.25, 625.00, 1,250.00 microg/mL respectively. The antibacterial ratios of the resin specimens incorporating with 5% of the three different ZnO were (93.58+/-5.95)%, (89.42+/-4.11)% and (78.97+/-3.90)% respectively, while after 3-month accelerating aging those were (89.01+/-7.91)%, (84.63+/-4.72)% and (72.27+/-3.89)%.

CONCLUSIONThe three different ZnO could improve the antibacterial activity of the composite resin. The nano-ZnO exhibit the strongest antibacterial activity, while the micro-ZnO weakest. The T-ZnOw presents comparatively strong antibacterial activity although with smaller specific surface area.