This is what I wrote to Lily:
Sealants are often put on molars to prevent decay.
But if your daughter is eating a good diet and complimenting that with oral hygiene and proper breathing (i.e. mouth closed /
nasal breathing), she shouldn't get cavities and therefore shouldn't need sealants.
(but most kids aren't so lucky, and don't have good dietary influence / habits, and so most kids do get cavities, and thus the sealant recommendation by many dentists)
Sealants are made of resin-based materials and can be a source of microplastics and other
chemicals like BPA that leech from the material.
Due to health concerns around BPA, manufacturers have moved towards alternatives like Bis-GMA, TEGDMA, or glass ionomers. Of course, these can have their own problems.
Overall my recommendation is to eat a healthy diet, brush your teeth, and breathe through your nose so that you won't get cavities.
Then there is no don't need sealants, or fillings, or any other dental procedures.
Like all medical interventions, there are risks and benefits to having things done and not having things done.
