Oh this is smart...just paint plastic on your kid's teeth to prevent cavities.
BPA or no BPA, it's still liquid plastic going in a kid's mouth. I wouldn't do it.
It didn't take more than five minutes to find this medical article about the toxicity of dental sealants: Dental Sealant Toxicity: Neurocutaneous Syndrome (NCS), a dermatological and neurological disorder by Dr. Omar M. Amin, PhD
Abstract: Neurocutaneous syndrome (NCS), a newly discovered toxicity disorder, is described in light of our new understanding of its relationships with the causative agents included in the dental liners used in afflicted patients. NCS is characterized by neurological sensations, pain, depleted energy and memory loss as well as itchy cutaneous lesions that may invite various opportunistic infections. Components in the calcium hydroxide dental sealants Dycal, Life and Sealapex have been identified as sources of the observed symptoms considered compatible with classical sulfa toxicity. Sulfonamide and neurological toxicity issues are discussed, three case histories are presented and an outline of management protocol is proposed. Additional notes on zinc oxide, Fynal, IRM and Sultan U/P sealants are also included.
Brush and floss...I've never had one cavity.