Decayed or damaged teeth can be treated by fillings when the affected area is not too big. There are 2 common types of dental fillings.
Composite Filling uses tooth colored plastic and glass mixture that can be bonded to tooth after removing the decay. This is more commonly accepted filling type since it matches color fo the teeth and requires less removal of tooth structure and has less risk of fracture of teeth around the filling.
Amalgam filling is a silver colored material that is a mixture of various metals and mercury. While it is more stronger type of filling compared to the composite filling it has higher risk of fracture of teeth around the filling. Amalgam filling also requires more removal of teeth structure compared to composite.