Yes, of course the zirconia microparticles do exert an effect on the surface roughness of the PMMA. Additionally, I want to clear it that when we talk about the effects of micro or nanoparticles, their effect is almost similar. So, whether you consider the effect of zirconia microparticles or nanoparticles, it will hardly make any difference. Please read the following review paper to clear all your doubts.

DOI: https://doi.org/10.1016/j.msec.2019.110292