Introduction. The lack of evidence regarding the best available material for restoring occlusal-proximal cavities in primary teeth leads to the development of new restorative material, with nanoparticles, in order to enhance mechanical properties, resulting in increased restoration longevity. Aim. To evaluate the Knoop hardness and bond strength of nanoparticles material glass carbomer cement (CAR) and high-viscosity glass ionomer cement (GIC) in sound and caries-affected dentin. Methods. Forty bovine incisors were selected and assigned into four groups (𝑛 = 10): SGIC, sound dentin and GIC; SCAR, sound dentin and CAR; CGIC, caries-affected dentin and GIC; and CCAR, caries-affected dentin and CAR. All groups were submitted to microshear bond strength (MPa). Knoop hardness was also performed. Bond strength values were subjected to two-way ANOVA and Tukey test. Knoop hardness data were subjected to one-way ANOVA. Results. GIC presented higher Knoop hardness (𝑃 < 0.001) and bond strength (𝑃 = 0.027) than CAR. Also, both materials showed better performance in sound than in caries-affected substrates (𝑃 = 0.001). The interaction between factors was not statistically different (𝑃 = 0.494). Conclusion. Despite nanoparticles, CAR shows inferior performance as compared to GIC for the two properties tested in vitro. Moreover, sound dentin results in better bonding performance of both restorative materials evaluated.