I have no idea what the professional literature recommends, but we have personal experience with this.  My then-2-yo son fell and dislodged 2 of his upper incisors, actually broke the alveolar bone segment rather than "knocked the teeth loose" but the effect was the same.  It was late on a Friday night (of course) and we didn't already have a pedi dentist for the kids, so we spoke to one of the residents at my children's hospital on the phone and I didn't ask about nursing because I figured that era was abruptly over.  

To my surprise, though, kiddo really wanted to try nursing early the next morning so I let him.  And it was pretty horrifying, as his teeth definitely moved as he breastfed but he still seemed to get comfort from it.  The dentist we saw 2 days later recommended that we not breastfeed any further because the bone fragment/teeth would not "stay" in place when she tried to reduce it and continuing to nurse would obviously allow things to shift around more.

I honestly didn't know what to do but it seemed likely that he would lose the teeth anyway so we ended up continuing to nurse.  Everything eventually mostly stabilized but he developed a small abscess a couple months later and they did need to be extracted.

Good luck to this family.  It was not a fun experience for us.

Best,
Sarah Reece-Stremtan M.D.

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