Stain on Baby's/Toddler's Teeth

[The Lioness]

Hello girls. My 15-month old baby boy has dark stains on his upper teeth from iron supplements. I tried cleaning them with a piece of cloth because I don't think the silicon toothbrush is doing much help. But that is not helping either. At ayaw na ayaw nya pinapakialaman ang bibig nya. He just bites me. Di ko pa din sya dinadala sa dentist though I'm really worried and I might just this weekend kapag free ang sched ko. And I'm not sure the dentist can clean his teeth since he dreads having his mouth opened and touched. Anybody ever had this too? Please share kung ano ginawa nyo. Thanks.