In order to test an effective biopolymer scaffold in promoting the growth of human dental pulp stem cells (HDPSCs), mesoporous silica @ hydrogel (MSN@Gel) nanocomposites are invented as a new type of biopolymer scaffold for HDPSCs proliferation in this paper. The expression levels of alkaline phosphatase (ALP), dentin matrix protein 1 (DMP1), and dentin sialophosphoprotein (DSPP) are significantly increased in the MSN@Gel group so as to better repair damaged dentin. In order to inhibit the proliferation of bacteria in the dental pulp, metronidazole (MTR) is loaded into MSN. The study found that MSN could effectively prolong the half-life of MTR by 1.75 times, and the viability of HDPSCs could be better maintained in the MSN-MTR@Gel group so as to better promote its proliferation to repair pulpitis. However, with the increase of the MTR concentration, its proliferation effect on HDPSCs decreased gradually, and the proliferation effect is the best in 10 μmol/L. Therefore, the MSN-MTR@Gel scaffold is expected to become an effective method for pulpitis therapy in the future.