The most common type of white fillings is the composite resin fillings. White fillings are desirable on front teeth for obvious reasons, as they mimic natural teeth in shape, colour and luster. They have been modified to be strong enough to be applied on back teeth as well.
The advantage of using them on back teeth besides the cosmetic effect, is that they prevent breakage as it happens when a tooth is heavily filled with amalgam, and if anything will break it is more likely to be the filling rather than the tooth. White fillings also depend on bonding to tooth structure, so there is no need for more drilling to make sure the filling is trapped inside the tooth, as is the case with amalgam fillings.
White fillings are packed into the cavity after applying a conditioner and the bonding agent. Then the filling is exposed to ultraviolet light to make it harden within the tooth. The next generation of white fillings is the flowable bulk fillers where the material is introduced into the cavity as viscous liquid and covers the entire cavity before being set by ultraviolet light.
The white fillings also contain fluoride that gets released into the tooth to prevent further decay under the filling.