I have large patches of enamel erosion all over my front teeth. I've tried many supplements, I eat healthy, but nothing really helped. My enamel would grow back, then wear away again. Then it dawned on me one day. I've recently, in the last few years, neglected brushing my teeth in the morning. I've come to only brush once at night, using gum or rinsing to freshen my breath in the morning. So I reverted back to brushing my teeth with any typical toothpaste, morning, 1 hour after lunch, and night. It's been less than 1 week since I've done this and my enamel has already grown back 35-40%.
Bacteria stains the teeth and wears away the enamel. Keep the mouth free of bacteria. This greatly helps with enamel growth.