Filings are mainly used to treat cavities, but are also useful in repairing cracked or broken teeth. Fillings are sometimes needed to repair damage to teeth from daily wear or tooth grinding. Local anesthetics are used to numb the area around the tooth before a filling, where special drills are used to remove cavities. Different materials can be used in fillings, including porcelain, silver amalgam, resin, or even gold. Each have different advantages and can be evaluated by a variety of factors, including durability, strength, aesthetics and expense.