I'm long-winded today, sorry!
I hate to be the bearer of possibly bad news, but that's how two of my son's teeth started. The two that he just had extracted b/c they had gone completely brown, started disintegrating, and one had an infection far up in his gums.

For us, it just seems to be genetics. My husband's babyteeth crumbled, and so did my FIL's. I was just happy it was only TWO of them.
Then again, it might also have been trauma, as he slammed his mouth into a table when he was 6 months old. At the time we focused on the accident because it caused a brand new bottom tooth to come out, but then later when those two upper teeth came in brown, we did wonder if he had hit his upper mouth as well, and sort of killed those two teeth. No way to prove anything, it's all just theories...
Anyway, we waited a good long while to take him in, b/c we figured there was nothing to be done, ya know? We tried to keep his teeth sparkling clean. We finally took him to a holistic dentist when he was around 18 months, and later she referred us to a pediatric dentist. After having full appointments with two (but having conversations with many), we found someone who really didn't care WHY it was happening, and just fixed the problem, and fixed it in the lowest impact way possible. He had two cavities filled (he needed NO medicine for the fillings, amazingly), and the two teeth were pulled with ONLY lidocaine. Other dentists were talking about general anesthetic, but I don't do GA lightly, and he's so compliant (with anyone but me!) I just didn't think it was needed.
Anyway, there are those who otherwise don't like fluoride but who DO put it on topically, just a TINY amount. I'm seeing more and more that the ingested fluoride doesn't do anything, and I personally still have my jury out on the topical thing, but others that I trust DO believe it can help.
We waited b/c we didn't see that there was anything a dentist to do so early. And we wanted to see what they would do. When the holistic dentist said that they would likely disintegrate and to just brush thoroughly and not worry about the teeth getting smaller, we did. They did get smaller but at some point they stopped disintegrating and even grew (from the root, I assume), but then the last dentist did ONE xray and saw that there was signs of an infection...and that's when we had them pulled.
When you DO feel that it's time to go in, be sure to get referrals from women here. If you can't get a referral, my advice is to just not mention nursing at night. No good can come out of that conversation, I've found.

: Well, unless you already know that they agree with you.

This last guy never even asked, he just wanted to fix the problem. The other guy we saw wanted to blame it on sugar, before he had even looked in DS's mouth, and he was just going by the current state of DH and my bodies.

:
Oh, and if/when you take him in, try to take your hubby/partner along. My husband works over the weekends, so he has some weekdays off, and it was VERY helpful to have him with us. In the first visits with the holistic dentist (she did three mini-visits rather than the one BIG first visit) we found that if I'm holding DS, he just wants to nuzzle my chest. But if he goes in ONLY with DH, he's a brave big boy and will do whatever the dentist asks. The first ped. dentist seemed to think I was a chicken for leaving the room before the examination, but the second guy was just happy that we had a plan, and a plan that WORKED.
OK, I have overwhelmed myself, I can't imagine what I've done to your brain.

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