Dental sealants are plastic coatings developed and used since the 1970s, to help protect teeth from decay. They are not a substitute for fluoride treatments as they are used only on the chewing surfaces of permanent back teeth.
They are usually applied during childhood, once these permanent teeth come in. In some cases, they can also be recommended in adults.
Sealants were developed because chewing surfaces on the molars and premolars have grooves that make them harder to clean and more prone to decay than other teeth. These fissures can be smaller than a single toothbrush bristle, so plaque accumulates in these areas, leading to cavities.