ZnO-Nanospheres Integrated Cement Improves Biological and Mechanical Properties

Objectives: Zinc oxide (ZnO) as an environment-friendly material has been used in various types of dental cements such as zinc oxide eugenol, zinc phosphate and zinc polycarboxylate cements, as well as endodontic sealers. ZnO nanoparticles (NPs) showed distinct optical and anti-bacteria properties as well as high surface to volume ratio. However, zinc polycarboxylate cement with integrated zinc oxide NPs have not been developed and evaluated to date. This study compared traditional polycarboxylate cements with our without ZnO NPs for biological and mechanical properties.
Methods: ZnO nanospheres were synthesized by a precipitation method in aqueous media from zinc nitrate hexahydrate and sodium hydroxide. Zinc polycarboxylate cement with different proportions of spherical ZnO nanoparticles was formulated and their biocompatibility, anti-bacterial property, mechanical strength as well as environment pH challenge resistance were comprehensively evaluated.
Results: The cement containing 5% and 10% ZnO nanospheres showed reduced solubility in artificial saliva at low pH environment (pH=3). The antibacterial activity was significantly improved by 40% for S.mutans and 90% for P. gingivalis when more than 10% (w/v) of the bulk particles were replaced by the nanospheres. The ZnO nanospheres also presented excellent biocompatibility to mammalian cells. In addition, 10% ZnO nanospheres augment cement mechanical properties by 1.2 folds for compressive strength and 1.5 folds for diametric tensile strength compared to conventional polycarboxylate cement.
Conclusions: This study revealed that dental cement with integrated zinc oxide nanospheres outperform conventional formulation in anti-bacterial efficacy and mechanical properties improvement as well as biocompatibility.