In countries with modern medicine and good medical ethics and short waiting periods, dentists normally put in a temporary filling after clearing a cavity or a root canal, instead of putting in a permanent one right away. Temporary fillings are far easier to remove, without damage to the tooth in question, and can be placed fairly quickly and painlessly. Considering I've had it happen that a root canal hadn't been done properly and had to be redone, I was very happy that didn't mean removing a permanent filling.
Of course,they're not as important if your permanent fillings are still old-fashioned metal crap that's going to come out in a few years anyway.