I don't know what the best combination is for those school. But I can tell you that I think dental schools understand that you can only get four, and are relatively lenient about the "types" of LOR you get. In my personal experience, I've gotten one orgo prof, one biochem prof, one english prof, and one from my research adviser.
I've gotten 8 interviews this cycle, my combination were not a perfect match for all of these schools. Some schools that I've interviewed at wanted a LOR from a dentist, and some wanted 3 LORs from science profs.
I guess this doesn't really answer your question. 😛 I just wanted to let you know you will still get interviews without matching up, so don't stress too much over it. Though I would give a call to your "dream schools" to make sure they have leniency on LOR types.
Hope this helps!
