Although gold is not so aesthetic because of its colour, even in our days it is still considered to be the standard of durability.
It has two reasons: on the one hand, up-to-date BioGold alloys, which are used for these kinds of fillings are bacterium-repulsive by nature. On the other hand, gold can be elaborated extremely precisely. Because of this, the fitting of the filling made in the technical laboratory is much better than that of the direct ones. After inlaying and fixing this filling into the cavity, much better closure is possible when the filling is polished on the merges of the tooth.
Although its colour does not suit the aesthetic expectations of the age, its extremely precise fitting and unique durability makes it the perfect solution in the case of the hardly visible, back, mostly upper molars.
Advantage: unique durability is a reference even in the case of bigger cavities.
Disadvantage: not aesthetic, it may cost a lot depending on the amount of gold used, at least 3 occasions are necessary (1. treating the decay, taking inlay-impression 2. gluing in 3. polishing the filling on the edge of the tooth)