The most important thing is phrasing the question.
You should ask them, “Do you feel that you know me well enough to write me a positive letter of recommendation for my application to dental school?“
You will find the occasional person who is not nice and won’t write a positive letter.
If they feel like they can’t do that, then they can say “No, I don’t know you well enough, but thanks for asking me.“
If they say yes, be ready with instructions on how to do it.
You should have ready to email them your CV. When you email it, remind them when you met, and in what capacity have they taught you.
Do not offer suggestions on what to say, other than the original question about writing a positive letter.
Good luck!