Anyone know anything about toddlers teeth turning grey?

It could certainly be from a medication he took. Check with your pharmacist. They can look up any medications he has taken and give you a print-out of the side effects.

It could be that he's getting too much iron. You should definetely check with the dentist. And please do not give or replace milk with juice, as suggested..this would not only increase risks of tooth decay, but will reduce you child's nutrient. You child should be drinking whole milk until he's 2. It's great that he's drinking water. You can also start brushing your baby's teeth. Usually just a soft brush or a wash clothe with water..you can try baking soda for the stain. However this could also be a dead tooth, that should not affect his permanent tooth.

it means that the tooth is dying, i had it happen to one of my teeth when i was younger. i dont think its anything to worry about since those are just baby teeth, but you may feel more comfort in talking to the doctor about it

I was told by my pediatrician 20 years ago when my daughter had the same problem, that it was caused by her going to sleep with a bottle in her mouth and that either the milk or the rubber on the nipple of the bottle were staining her teeth... If it takes going to sleep with a bottle in his mouth to get him to sleep, then give him more juice in bottles instead of milk at that time only and dont send him to bed with a bottle in his mouth with milk in it... Never delete milk altogether... Only at bedtime... Also, going to bed with a bottle in his mouth can cause him to have buck teeth, by sleeping with the bottle in his mouth...I hope I explained all this clearly enough to you...

Has your child had an impact to the mouth? If so, then the tooth could be (as an earlier post said) dying. Some people refer to it as a "shocked" tooth. You definitely need to take your child to a dentist for an evaluation. There is a chance of an abcess forming over time. My child fell at around age 2, the abcess was found at about age 4. It required the tooth to be removed and a spacer to be placed in his mouth to maintain the proper spacing for permanent teeth to erupt. It also was a front tooth and had a false tooth in place which served for cosmetic reasons. I know it is difficult at time to find a dentist to accept a child as young as yours but they are out there. It is best for your child to learn early on that a trip to the dentist is nothing to fear. My 27 month old had a fall and had to have xrays at the dentist when he was 22 months old. He was great about it all and now loves to go to the dentist.