They are generally placed in children and teenagers, not on baby teeth and rarely in adults.
The best time to place the fissure sealant is when the adult tooth has just erupted and certainly within two years. For the first permanent molar, this would be around the age of 6 years old and for the second permanent molar, the age of 12.
The reason it is best to do this as soon as possible after the tooth has come through, is because this is when the enamel of the tooth is at its weakest. Dentists would refer to the enamel as being ‘immature’ meaning it hasn’t been exposed to the mouth and fluoride for long enough to toughen up.
Having said that, you can get decay in the patterns of your teeth (pit and fissure caries
) at any age- you are just more vulnerable and likely to have problems shortly after the tooth has come through.
In adults, sometimes we do something called a PRR- a 'Preventative Resin Restoration' . This a combination of a small white filling
- aka a 'resin restoration', in the top of your tooth (where decay has occurred) and a 'preventative' fissure sealant (to protect the remaining pattern from future decay).