every school's LOR requirement varies slightly. It's not a one-size-fits-all thing. Do your homework, make a list from schools, and match the requirements up to what you have.
This combo seems to meet 85-90% of all the schools requirements: 2 science profs w/ one in your major if STEM, 1 non science (non stem prof, volunteer, dentist, etc), and a supervisor letter (work, volunteer, research, etc).
You do not need 2 dentist LOR's unless one is from shadowing and the other is from volunteering and they can be used to satisfy a schools "supervisor" requirement or a non-stem requirement. Again, do some due diligence and check every school's requirements, don't assume things.