Sealants are a great way to help prevent cavities from forming in the first place. The best time to have a sealant placed is shortly after the new adult molar tooth erupts and only when it has naturally deep grooves - ones that are hard for a toothbrush to sweep down and clean out. Even if the grooves are only moderately deep, it still might be a good idea particularly if several other teeth have already become decayed. My office places sealants a little differently than most other offices. In most cases, I will use a special soft isolation device to make sure that the tooth stays completely dry during the entire procedure. A perfectly dry tooth is critical for the sealant to bond to the tooth making a good...well...seal. We also use gentle air abrasion to clean off the molecular biofilm and fluorapatite layers--both will prevent a good bonding. I have found this to provide the most predictable and longest lasting restorations, which is important because a preventative procedure should prevent future problems.