The Dental Clinic at Primary Children’s Medical Center is one of the last places you might expect to find a former major league baseball player, especially one with a sparkling World Series championship ring. Yet there is Brian Banks, standing 6-foot-3 and dressed in green scrubs, in the final weeks of his residency. Becoming a pediatric dentist is a goal the 42-year-old has worked toward since retiring from baseball in 2004.