Its 21st Century, Silver Filling is now obsolete. We use a composite (white) filling is used to treat a decayed tooth which is as strong as silver amalgam and no one can figure out if the tooth is treated or not. The material is inserted into the tooth where it then prevents the further spread of decay or repairs any damage.
The composite white filling is a synthetic combination of acrylic resin and glass which has a white color thereby enabling it to match the color of the tooth. This is also chosen for aesthetic reasons as many people prefer to have fillings which match the rest of their teeth rather than the distinctive silver filling. Composite white fillings have a natural color which is similar to the color of your natural teeth and so blends it well with them.