You should not use the same keyword in all title tags. So this would be the wrong way to do things
Springfield IN Dentist | Springfield Dental Care Experts - Dental Surgery
Springfield IN Dentist | Springfield Dental Care Experts - Dental Fillings
For city specific keywords first make sure they get traffic by doing some research. If they do then you can target those kinds of phrases within the site.
If not I would target generic phrases such as "dental surgery" and have locations pages set up to assist with your geo targeting.