i don't think its autism related, but it could be something that is hereditary. some kids lose teeth and get new ones quicker than others, i have 3 kids and they all were different when it came to teeth.
Don't know either but my little ones teeth were slow coming in, too. And they came in wrong so we had to remove a lot of them in the hospital.
I didn't have a diagnosis then so didn't relate to autism.
My nutrition was poor when I was pregnant with my last kid due to having gestational diabetes. I couldn't keep food down very much and was hospitalised a few times throughout the pregnancy due to incessant vomiting. Eventually, I had to use incilin and go on a very meagre and strict (and unhealthy) diet.
This affected the baby, since she wasn't getting much nutrition either..mainly proteins and calcium were lacking which resulted in very weak baby teeth.