An infiltrant comprising from 90 to 99.9 wt.-% of at least one polymerizable monomer, oligomer or prepolymer and from 0.05 to 10 wt.-% of a polymerization initiator, the infiltrant having a dynamic viscosity of 0.3 to 100 mPa·s (23° C.)； for use in a method for strengthening a fixed ceramic dental prosthesis in the oral cavity.
