Silver fillings, or Amalgams, are a mixture of several metals (Silver, Zinc, Tin) and Mercury.
All legitimate studies have shown that these fillings are safe and do not cause chronic disease as far as we know. This is one of the most time-tested materials in dentistry, short of gold. That said, amalgam use has dropped off considerably in recent years mostly becasue of the unatural look of these restorations.
White fillings are made of a composite quartz resin. It comes in many color shades and is great for restoring a natural appearance. They are also referred to as composite restorations.
White fillings were originally developed for use in the front teeth but today most patients prefer composites in all sites because of their obvioius esthetic advantages. Today's modern white fillings have replaced amalgam in most applications.