Yes, properly placed and monitored sealants do prevent cavities. A sealant is a material that flows into the tiny pits and fissures of a tooth. It seals off this area and does not allow bacteria to get in. If bacteria does get into the pits or fissures of the teeth, a toothbrush bristle is way too big to get them out. By sealing off the pits and fissures it keeps these areas clean.
It is important to know that sealants do fall out occasionally and need to be put back in. If they are not examined regularly, cavities can still develop.
Lastly, it is worth mentioning the history of sealants. For almost 5 decades insurance companies did not want to pay for them. Eventually even the insurance companies realized that sealants would prevent cavities and other more expensive dentistry. Now almost all insurances pay for sealants. Hope this helps
My best to you!
William F. Scott IV, DMD