To evaluate the antimicrobial properties of 2 different pulp capping materials (ProRoot MTA and iRoot BP Plus).

Modified direct contact test (DCT) was performed as follow. ProRoot MTA and iRoot BP Plus were set for 7 days, then crushed and immersed into deionized water at concentrations of 200 g·L^-1 for another 7 days. PH values of the supernatants of the aqueous extracts were measured with a pH meter. The germfree superna-tants were mixed with Streptococcus mutans suspensions and then incubated for 24 hours. The survival of bacteria wasassessed by measuring the optical density (OD) at 600 nm with an automated microplate reader.

PH values ofthe aqueous extracts of ProRoot MTA and iRoot BP Plus were between 12 and 13, and no statistically significant difference was found (t = 0.133, P = 0.899). Both ProRoot MTA and iRoot BP Plus demonstrated good antibacterial properties (P＜0.05), and iRoot BP Plus performed a better antibacterial effect (P＜0.05).

IRoot BP Plus performed a better antibacterial effect against Streptococcus mutans when compared to ProRoot MTA.