Nanoneedle-like zinc oxide as a filler particle for an experimental adhesive resin.

Aim: The aim of this study was to develop an experimental adhesive resin with nanoneedle-like zinc oxide (N-ZnO), an inorganic filler, that could avoid particle agglomeration and lead to a homogeneous stress distribution within the material and characterize it.

Materials And Methods: N-ZnO particles obtained by a thermal evaporation technique were characterized regarding size and surface area and added at 0 (control), 1, 2, 5, and 10 wt%, to an experimental adhesive resin. The following experimental adhesive resins' properties were assessed: radiopacity, contact angle to conditioned enamel and dentin, color, degree of conversion, flexural strength, resistance to degradation, and cytotoxicity. Statistical analysis was performed using one-way ANOVA and Tukey's post hoc test and paired Student's t-test.

Results: Particles presented a mean particle size of 40 nm and a specific surface area of 16 m/g. N-ZnOshowed an increased radiopacity when compared to N-ZnO. Contact angles were significantly higher for N-ZnOat enamel and N-ZnO, N-ZnO, and N-ZnOat dentin. All groups showed color change when compared to N-ZnO. Higher the N-ZnO concentration, lower the degree of conversion. There were no significant differences between the groups for flexural strength and resistance to degradation. The addition of N-ZnO showed no difference in cytotoxicity when compared to positive control, N-ZnO, and all groups showed higher values than negative control.

Conclusions: N-ZnO possibly exceeded potential limitations due to particles' agglomeration and improved the transference and distribution of stress within the material. It could be effectively used as a filler for adhesive resins.