S.R.
My daughter is 17 1/2 months, she doesn't take a bottle anymore, or a nightime sippy of milk., but I only brush her teeth about every other day, usually after breakfast. It's too hard to keep her hands out of her mouth and off of the toothbrush and keep her mouth open and tounge inside with my 2 hands haha, I would give him some time. I let her brush her own teeth daily, which means she just chews on her toothbrush for about 15 minutes, I think it gets them clean enough.