Sealants work by filling in all the crevasses on the chewing surface of the tooth, shutting out food particles that may get stuck there and then cause decay. Typically it will be applied to “tricky” teeth such as back molars. This is because even with good brushing habits, a toothbrush may not reach all the way back every time. Applying sealants is quick, painless, and easy, and protects the teeth for a long time.