When decay gets down below the surface enamel and into the dentin of the tooth, we must remove the cavity and fill that space with a restorative material to preserve the tooth.
Composite/Resin fillings are tooth colored fillings that are typically used when aesthetics are involved. As any type of filling material, they have their pros and cons. They work well in the front of the mouth, but often times they are not feasibly in the back of the mouth. They are very technique sensitive and require the working field to be dry while placing. As you can image, the back of the mouth at times can be very challenging and sometimes impossible to keep dry. In these instances, the dentist will recommend a silver/amalgam filling. They also typically do not last as long as a silver filling and can be quite sensitive for up to months after placing.
Amalgam fillings are silver colored fillings that work very well in the back of the mouth. The back of the mouth takes a lot of force and because of their content; these types of fillings are able to withstand those forces. These fillings typically can last longer than a composite filling. Another positive aspect about this type of filling is it has a lot less post operative sensitivity than the composite fillings.