The bacteria or plaque that is left to sit on your teeth produce acids that dissolve your tooth enamel and form a cavity. Once this outer, tougher layer of your tooth is compromised, the acid can quickly eat away at the next, softer layer called dentin. If it dissolves the dentin and reaches the nerve, a root canal will be needed. Sealants are a cover that can be placed on the tooth surface to make it less susceptible to cavities. But since these can wear off over time, they should be replaced periodically. Cavities that are detected early, either by means of radiographs or laser cavity detection, are easy to fix with a filling. Once it reaches the nerve, a root canal, buildup and crown will be needed.