At my office, I exclusively use composite materials for filling or restorative procedures. I do place patients concerns about mercury presence in old amalgam or alloy based metal restorative material. However, that is not the main reason I choose to use composite material. Composite restoration allows active bonding thus seal between the filling material and tooth structure. Also, the material is becoming more and more similar to natural tooth structure mechanically, meaning the hardness, and 'stretchability' of the material is getting similar to that of natural tooth structure. Active bonding and mechanical property matching of composite material in my opinion helps prevent further loss of tooth structure moving forward.