It's probably a good idea to have detist you shadow write LOR for you. I assume you need about 3 LORs; 2 from science professors and 1 from your professional field (from dentist, work, etc...). I had LOR from my dentist that I shadowed about 6 months and he wrote a good LOR for me. When I called NYU admission lady told me LOR from dentist is more suitable. It's best to call the school and find about the requirements. Good luck!!!!!!!!!!!!!