Brushing and flossing are the best ways to help prevent cavities, but it is not always easy to clean every nook and cranny of your teeth – especially those back teeth you use to chew (called molars). Molars are rough, uneven and a favorite place for leftover food and cavity-causing bacteria to hide.
Still, there is another safety net to help keep those teeth clean. It is called a sealant, and it is a thin, protective coating (made from plastic or other dental materials) that adheres to the chewing surface of your back teeth. They’re no substitute for brushing and flossing, but they can keep cavities from forming and may even stop early stages of decay from becoming a full-blown cavity.
Children and adults can benefit from sealants, but the earlier you get them, the better. Your first molars appear around age 6, and second molars break through around age 12. Sealing these teeth as soon as they come through can keep them cavity-free from the start, which helps save time and money in the long run.
It is a quick and painless process. Your dentist will clean and dry your tooth before placing an acidic gel on your teeth. This gel roughs up your tooth surface so a strong bond will form between your tooth and the sealant. After a few seconds, your dentist will rinse off the gel and dry your tooth once again before applying the sealant onto the grooves of your tooth. Your dentist will then use a special blue light to harden the sealant.
"Quoted from Mouthhealthy.org"