UNC and UDM. Of the 10 schools I applied to those two required Dentist LORs. UNC didn't call me for an interview (though that might be a case of Tufts syndrome or they just knew it wasn't my top pick...or they just didn't like me for the missing LOR). UDM called me for an interview but I had to reschedule and eventually cancel once I got into my top choice.
Some schools aren't too particular about this. Each school has this listed on their website. Take the time to research your schools thoroughly and you'll know for yourself.