Dental cement's biological and mechanical properties improved by ZnO nanospheres

Metal oxide nanoparticles are a new class of important materials used in a wide variety of biomedical applications. Bulk zinc oxide (ZnO) particles have been used for temporal or permanent luting cement because of their excellent mechanical strength and biocompatibility. ZnO nanoparticles have distinct optical and antibacterial properties and a high surface-to-volume ratio. We investigated the mechanical and antibacterial properties of luting cement with different ratios of ZnO nanospheres. We showed that luting cement with 5% and 10% ZnO nanospheres was less soluble in low-pH (pH 3) artificial saliva. Antibacterial activity was 40% higher for Streptococcus mutans and 90% higher for Porphyromonas gingivalis when >10% (w/v) of the bulk particles were replaced with ZnO nanospheres in ZnO polycarboxylate cement. ZnO nanospheres were also biocompatible with mammalian cells. Additionally, the compressive strength was 1.2 times greater and the diametral tensile strength was 1.5 times greater for cements with 10% ZnO nanospheres than for conventional ZnO polycarboxylate cement. We propose a new method for improving dental luting cement by integrating it with ZnO nanospheres. This method simultaneously adds their greater antibacterial, mechanical, and acid resistance properties and retains an outstanding degree of biocompatibility.