OBJECTIVES: To evaluate the effect of incorporating zinc oxide nanoparticles (ZnONPs) and sodium trimetaphosphate microparticles (TMP) into resin-modified glass ionomer cement (RMGIC) on its physicomechanical, microbiological, and cytotoxic properties.

METHODS: Six groups were prepared: 1) RMGIC (Fuji II LC); 2) RMGIC-1.0 %ZnONPs; 3) RMGIC-2.0 %ZnONPs; 4) RMGIC-14.0 %TMP; 5) RMGIC-1.0 %ZnONPs-14.0 %TMP; and 6) RMGIC-2.0 %ZnONPs-14.0 %TMP. Tensile/diametral compressive strengths (TS, DCS), surface hardness (SH) and degree of monomer conversion (%DC) were evaluated in 24 h and 7 days. Fluoride (F) release was assessed over 15 days using alternating demineralizing/remineralizing solutions. Antimicrobial/antibiofilm activity against S. mutans (UA159) was assessed through adhesion, biofilm growth measurements, and XTT assays. Cytotoxicity was tested on MDPC23 odontoblasts using the resazurin assay.

RESULTS: The DCS for the RMGIC-2.0 %ZnONPs group was 22.5 % higher when compared to RMGIC after 24 h (p < 0.05); after 7 days, RMGIC-2.0 %ZnONPS-14.0 %TMP group was 23.4 % higher than RMGIC (p < 0.05). For TS after 7 days, the RMGIC-2.0 %ZnONPs-14.0 % TMP group showed the highest values (37 % and 55.4 %) than RMGIC and RMGIC-14.0 % TMP, respectively (p < 0.05). At 24 h, the RMGIC-2.0 %ZnONPs-14.0 %TMP group showed the highest SH among all groups (p < 0.05). The greatest effect on reducing bacterial viability was observed for the RMGIC-2.0 %ZnONPs-14.0 %TMP group (p < 0.05). For cytotoxicity analysis, at 24 h, the RMGIC-1.0 %ZnONPs-14.0 %TMP group showed the highest cytocompatibility (p < 0.05). At 48 and 72 h, RMGIC-1.0 %ZnONPs, RMGIC-2.0 %ZnONPs, RMGIC-1.0 %ZnONPs-14.0 %TMP and RMGIC-2.0 %ZnONPs-14.0 %TMP groups showed the lowest cytotoxicity (p < 0.05).

CONCLUSION: Incorporation of 2.0 % ZnONPs and 14.0 % TMP into RMGIC significantly enhanced its physicomechanical and antimicrobial properties while simultaneously reducing cytotoxicity.

CLINICAL RELEVANCE: The new restorative material containing TMP and ZnONPs could be a promising biomaterial, enhancing biomineralization and providing anticariogenic benefits.