Hamadan University of Medical Sciences Avicenna Journal of Dental Research 2423-7582 4 1 2012 06 29 Comparison of the Effect of Metallic Nano-particles on the Water Contact Angle of Composite Resin 33 39 EN M Shirinzad Sh Kasraei M Azarsina Journal Article 2012 03 26 2012 05 05 Statement of the problem: Addition of metallic nano-particles to composite resins can change their water contact angle. Purpose: The aim of this study was to evaluate the effect of addition of nano-particles of silver and zinc oxide to composite resins on their water contact angle. Material and Methods: This in vitro study was performed on 60 composite resin samples. Nanosilver and nano-zinc oxide were added to composite resin at 0.5% and 1% by weight. SEM-EDX analysis was performed to confirm the homogeneity of the nano-particle distribution. Composite resin discs were made in molds measuring 10 mm in diameter and polished with silicon carbide papers. Water contact angle measurements were performed on 4 points on the surface of each sample, and the mean of the points was reported as the water contact angle of the sample. Twoway ANOVA, followed by the Tukey-HSD test and independent t-test with a significance level of 5%, were used for data analysis. Results: The addition of nano-particles caused a reduction in the contact angle between water and composite resin (P=0.000). The interaction of the type of nano-particle and its concentration on the contact angle was significant (P=0.000). Water contact angle varied depending on the type of nano-particle (P=0.000) and its concentration (P=0.028). Conclusion: Addition of silver and zinc-oxide nano-particles to composite resin reduced the water contact angle of composite resin.