The so called potential hazards you read about is a controversy that has been going on for decades, with almost no proof at all. I would not worry about silver fillings from that perspective.
Normal depends on the office, some use more amalgam, some more composites. When I say composite, thats what the filling is called. There are only two main types of fillings, white composites and silver amalgams.
You are correct, most crowns require a buildup, which is basically a filling under the crown. What material does not matter much. Amalgams are a little stronger, and under a crown would not pose any problem even according to the group that claims they are hazardous. But newer composites are almost as good.
What is filling normally used .They normally do filling and then they put a cap .
What should the composite filling be (what material).I read and understood there seems a big debate between potential hazards of using Silver amalgam fillings .
Removing the pulp tissue of a tooth dries it out and weakens it. All posterior teeth that have been root canaled need a crown to prevent the tooth from splitting. Anterior teeth should get a crown or composite filling to strengthen the tooth. Silver fillings are not an option for a tooth that has a root canal.