Silver fillings are in by mechanical retention and compared to tooth coloured fillings, they lack the chemical bond and seal that is ideally needed. Thus, when a magnified silver filling is seen, there is often a defective margin between the filling and the tooth. This however needs to be assessed by the dentist to see whether it needs to be replaced or not. Replacing them in general will result in a more natural looking long term solution by removal of the old mercury contained metal fillings.