Toothbrush bristles cannot always reach all the food matter that finds its way into the grooves and uneven surfaces of the teeth. Sealants can be applied as a preventive measure to smooth over rough or irregular areas to keep plaque from collecting, and cavities from forming. Sealants are typically made of a plastic resin which safely and quickly adheres to the teeth and, with proper care, can last for many years.
While the life of the sealant may be for a long time, your dentist may choose to periodically maintain the sealants by reapplying them. This is also necessary to ensure that any weak areas of the tooth's enamel are protected from decay which would otherwise lead to cavities and possibly tooth loss. Weak enamel, typically found during the x-ray portion of the annual dental exam, should not be treated lightly as it is a very vulnerable part of your oral health.