A system includes a dental appliance having a polymeric shell with a plurality of cavities for receiving one or more teeth; and a biocompatible cosmetic aqueous liquid in the cavities of the polymeric shell of the dental appliance. The aqueous liquid includes a viscosity modifier chosen from a water compatible polymer, a polysaccharide, a silica compound, and mixtures and combinations thereof, a tooth re-mineralizing agent, and water. The aqueous liquid is substantially free of tooth whitening agents and fluoride, and has a refractive index of greater than 1.3 at room temperature.