Our youngest son had two molars like that at exactly the same age, and they said that because I have an autosomal recessive immunodeficiency (dysgammaglobulinemia Janeway B) the problems with our son's teeth could be amelogenesis imperfecta as well.
She's also right. Subclinical infections, sometimes ones you don't even know about, can do that... and that's all we can put it down to with our son, because it was the only two he ever had. With him, the enamel crumbled last, so the first we knew of it, was almost hollow teeth.
He's had no problem since then, so the worst prognosis isn't necessarily the only prognosis. But part of that, was that it brought him up with a start. He'd cleaned his teeth, but not been flossing, or as diligent as he should have been round the back. Now he's a toothbrush flossing diligentee.
In your case, the diagnosis may, or may not be right. Time will tell.
With my immunodeficiency though, I found that minerals, vitamin C and changing my diet to include way more raw foods seemed to bridge some of the gaps for me, and make everything work a lot better.
I've found I have much higher requirements for certain minerals than "normal" people do, especially (but not exclusively) magnesium, which is interesting, because magnesium holds the calcium into bones. I have to take four times the recommended daily allowance of magnesium. I'm sure that with some genetic conditions, particularly if the effect is caused by methylation (epigenetics) the mineral absorption pathways aren't as secure as otherwise would be the case. In my case, my gut flora had also been damaged by years of antibiotics, until I became severely allergic to them, and I didn't know that you need decent gut flora to absorb minerals properly. It took a while to get the gut flora back working as it should. So for me, that was an issue.
I've got no genetic expertise, but have gone into it in some depth, because supposedly in order to survive, I'm supposed to have immunoglobulin monthly, but didn't want to do that, since it carries other risks for those with a dicey immune system.
I can't have antibiotics so in order for me to live, its my way, or the byway
. And sometimes we parents are the only ones who can provide the answers.
Certainly a whole lot of things have improved for me, including my bone density. An x-ray done by the dentist recently, showed that my "bone cap" was good and solid, supposedly unusual in someone my age and with my history. She was expecting to see none, and she and I were pleasantly surprised. And I've had very few fillings in the last few years, so that shows me that there has been an improvement. My mother had no teeth 15 years before the age I am now, so I'm doing okay... So two issues have improved.... my teeth are better, and I get far fewer infections than would be expected with someone with an autosomal recessive disorder.
So people with genetic conditions definitely do need to fine tune what they do, supplement wise, and might need more nutritional support than others.
Our son's problem brought us up with a start, because we'd assumed he was normal, though healing was slower with him, and had keloid tendencies. We now know, after tests done a couple of years ago (he's now 22) that his immune system is very like mine is, but not as bad. So I have to be careful with him, and though he hates it, every day he gets a huge helping of rabbit food
and a mineral supplement designed specifically for our soil deficiencies here. He grumbles and grizzles, but a lot of things have gone better with him since then.
Have you had a dental Xray done on him? What was his bone cap like? If its good, then it might be one of those things, but if its not so good, you might want to talk to someone about an ankle bone scan (or whatever they do in your country) to see if its affecting the body bones as well. That might not be such an issue now, as bone is so bendy in kids, but if the areas of bone that are solid aren't as dense as they might be, you might want to talk to someone about that, because that might cause problems later, once the growth plates close.
Just thinking ahead to questions you might want to research... because often what happens in teeth, happens in bones. I can understand your caution. Nothing more important then the scaffolding, coz we have to hang the rest of the furniture on it... or chew with it