Sealants are used to protect your back teeth (molars) against tooth decay and cavities. These teeth are vulnerable to cavities and decay because they are the most difficult to reach and clean. It is best to have a sealant placed when the molars first come in (adult molars usually emerge at age 11-14) to ensure they are protected early. Sealants form a barrier between your tooth and any plaque, food particles, and bacteria. Sealants last for about 10 years and can be reapplied if necessary.