Reply to Tooth Decay

I just took my daughter to the dentist too she is 14 mo and also has cavities the dentist told me that there is a liquid that they can apply in their teeth that helps to hardened them but that it turns the teeth black, I chose that she has another appointment next month to see if it’s helping if it is they will reapply it, it doesn’t look nice but if it works at least she won’t have to have something more invasive