Hi T. - I'm so glad you asked, I wish I'd asked the same question 4 yrs ago....my dghtr wldn't drink milk out of a sippy cup when we moved away from the bottle. In order to make sure she rcvd enough calcium we moved to OJ & I didn't dilute it. (She also ate yogurt.)
I also asked our ped. if drinking OJ all the time was okay & she said it was fine (she only had a max of 16oz/day).
What I didn't know then that I know now it that OJ is very acidic on the teeth, can wear away the enamel and is very sticky on teeth! I'm pretty sure all these things were the main causes of my dghtr already having 6 cavities (at 6 yrs old)! It doesn't help that her teeth have very deep grooves that trap the tiniest plaque (that cause cavities), but I didn't know abt her teeth when I was giving her the OJ for so long.
If you continue giving him OJ just make sure he rinses with water really well after he finishes the OJ. I also thought running a plain toothbrush over all the teeth after OJ wld be in order also, but a friend of mine who is a dental hygienist said that is actually a bad thing due to the acidity of the OJ, a toothbrush would just rub the acid OJ further into the teeth, etc.
K.