They both have genuine smiles on their faces and greet you warmly.
They both make the patient or student feel comfortable. Today my dentist offered me a blanket while he was performing the procedure on my teeth.
They both explain what they're doing; the dentist describes the procedure as it's happening and the teacher coaches the student as she teaches.
They both use soft voices and answer any questions as carefully and completely, as possible.
They both make you want to stay.