These are white ,tinted or clear plastic coating/cements that are flown into the fissures/grooves on your back teeth ,mainly chewing surface of molars and premolars to protect them from decay . These fissures and grooves are naturally occurring on chewing surfaces of teeth and are more prone to develop tooth decay than the other tooth surfaces. In some these can be very narrow and deep making them hard to clean and traps food and bacteria which produces acids that attack teeth and cause decay.
It is best done on newly erupted permanent teeth. mainly done on the molars and premolars. It can be done on baby teeth and to preserve healthy teeth in adults as a safeguard.
sometimes if done at the right time early initial tooth decay can be treated with a fissure sealant instead of a filling.
Fissure sealants can wear away or be lost and can be reapplied if needed. A protected tooth has only half the risk of tooth decay as compared to an unprotected tooth. However the dentist cannot guarantee the prevention of decay on all tooth surfaces.