Should sealants be placed on my child's teeth?

Sealant is a coating, chemically related to composite resin filling material but more liquid in consistency, that is placed on the chewing surfaces of permanent molar (back) teeth.  When cured by exposure to a curing light, hardened sealant is a thin, plastic-like barrier that prevents cavity-causing bacteria and food debris from collecting in the deeper grooves and pits of the tooth, greatly decreasing the chance of getting a cavity on that surface of the tooth.  Sealants are not exceptionally durable, and can last anywhere from 3 to 15 years.  Most advisory groups and panels recommend the placement of sealants on the permanent molars of all children.  Here is another area where we vary a bit from the majority.

Teeth absorb minerals.  Adding fluoride to toothpaste uses that property to advantage.  As a result, most people's rate of getting cavities goes down as they get older and their teeth have absorbed more minerals.  If sealants are placed on the molars of a six year old and are worn off by age 18, because mineral absorption has been physically blocked by the sealant, that 18 year old will have the same decay resistance she had as a six year old.  If the six year old appeared to have a high chance of getting a cavity, the sealant is a good thing to have done; if the six year old appeared to have a low rate of decay and little chance of getting a cavity, the sealant may have been a negative.