White fillings are an esthetic and conservative treatment choice when it comes to getting a tooth filled. When teeth are decayed, they need to be filled. Traditionally, a "silver" or "amalgam" filling was used to fill the cavity. Through advances made in dental science and materials, nowadays we are able to fill cavities using "white" or "tooth-colored" fillings. These fillings mimic the natural shade of the tooth, are practically undetectable and provide excellent function for many years.

It should be clear why white fillings are considered an esthetic choice. But what makes them a conservative choice? A “filling” is a “filling”, right? Not exactly.
With silver fillings, a certain amount of tooth has to be removed for the silver filling not to become too weak and break. It doesn’t matter how big or small the cavity in the tooth is. This doesn’t make much of a difference if the tooth has a large cavity, but what about the tooth which has a small cavity starting. It is not considered “conservative” treatment to take away healthy tooth to place a silver filling there. That’s where white fillings have another decided advantage. White fillings are bonded to the teeth chemically. They don’t need to be of a certain size for them to work. They could be as small or as big as necessary.
Another reason that white fillings are a superior choice to silver fillings is because of the fact they are bonded on to the tooth. This “bonding” also strengthens the tooth by holding the different parts of the tooth bonded on to the filling.
And yet another reason favoring white fillings over the silver fillings is the fact that silver fillings contain mercury. Mercury is a highly toxic and poisonous chemical. It is used in very small concentration in the process of making the silver filling material.
If you have old silver fillings, they should be replaced before they start rusting and corroding, which happens to almost all of the old silver fillings.