One of the oldest filling materials is dental amalgam. It was called “amalgam” because it was an amalgamation of five different materials including mercury. Even though the mercury is bound, and amalgam fillings did a really good job of fixing holes, the fact that it was visible as black as well as the mercury content concerned the public. People wanted something cosmetically pleasing that could fill the hole and still look good. This led to the introduction of composite resin – a white plastic filling material. Whilst this looks better than the old amalgam, it shrinks on setting, so fails over time to completely seal the hole.
For some time, dental gold was also used. You may still even know older family members or friends with a gold tooth. Gold is very stable, but dental gold is expensive and stands out.
As such, dental ceramics, better know as porcelain, became available. Despite being more expensive, they are dimensional stable; this means they do not shrink. In the long term, they are the best material at both: filling the hole in the tooth and being cosmetically pleasing.