Chicken eggshells contain calcium carbonate. Calcium carbonate sized nanoparticles can mineralize carious teeth. This study aims to optimize the concentration of xanthan gum as a viscosity modifier in calcium carbonate nanoparticles which has the most stable physical properties. Chicken eggshell extracted into calcium carbonate and then calcium carbonate nanoparticles using the top-down method using high energy ball mill formulated in toothpaste with xanthan gum concentration of 1.3; 1.7; 2.1; 2.5; and 3.0%. Tests were carried out on organoleptic and centrifugation, carried out for 6 weeks on homogeneity, pH, dispersion, foam height, and viscosity. The results of viscosity are 83,467 - 420,000 cp, which shows a decrease and spread of 1.70 - 3.56 cm showing an increase from FI - FV. From the research it can be concluded that the use of xanthan gum in the calcium carbonate nanoparticle toothpaste which is best in physical properties is formula II.