Lapis impregnation - a technique of soaking the surface of a milk tooth with silver nitrate solution. This method is used when a large part of a tooth surface is affected with caries, making filling insertion impossible. Silver, which is released from the solution, has strong antibacterial properties. This allows to arrest caries and prevent tooth extraction. It is very important as premature milk teeth extraction may later lead to malocclusion. However, this method results in staining the tooth with a characteristic colour of blackened silver. Lapis impregnation is used for the milk teeth with extensive and flat cavities which form on the smooth surfaces of a teeth. The treatment is painless.