Many cavities start in the occlusal or biting surfaces of back teeth.  These surfaces are uneven with cracks (fissures) causing food impaction and plaque build up, which may lead to decay.  Fissure sealants may be recommended in primary teeth but most commonly are applied to the 1st permanent molars that erupt age 6-7 years, ideally as soon as they are fully erupted.  In Irish children 80% of decay is found on the biting surfaces, which could be prevented by sealants.

A fissure sealant is a varnish layer, which is applied to the occlusal surface of at risk teeth, flowing into the fissures, creating a shallower, smooth surface.  Research has shown excellent prevention of decay in sealed teeth.  Sometimes a fissure sealant can be placed on a tooth that has already begun to decay, as the sealant will prevent further spread of the infection.  Fissure sealants are only effective as long as they are intact so need to be monitored frequently and refreshed if necessary at review visits.  When applied under ideal circumstances they will last many years, but may be dislodged by sticky foods.