Cerium oxide nanoparticles could put a stop to tooth cavities. These nanoparticles could inhibit the formation of the biofilm on teeth, known as plaque, created by bacteria. In this work, nanoparticles of cerium oxide were generated using Supercritical antisolvent (SAS) process followed by a calcination process. The use of supercritical fluids and particularly SAS process to prepare nanoparticles removes the drawbacks of the conventional techniques such as excessive use of solvent, thermal solute degradation, high residual solvent concentration, and mainly difficulty in controlling the particle size and particle size distribution during processing. In the first step, nanoparticles of cerium oxide have been precipitated by SAS process. In this preliminary work, the influence of the pressure on the particle size, particle size distribution, morphology, and specific surface area of these particles have been investigated. Most of the experiments led to successful precipitation of a cluster of particles in the nanometer range. In general, the morphology was greatly improved to spherical nanoparticles. Particle size was higher when the pressure was lower. The specific surface area increases dramatically after the SAS process, from 0.46 m2/g to a gap between 27 m2/g and 197 m2/g.