Yes.
The average applicant comes from a liberal arts background. A liberal arts curriculum encourages, and is inherently defined by, the breadth of educational exposure. You are pushed to take a wide spectrum of classes designed to help nurture the development of a well-rounded graduate. It is never a waste of time to take classes outside your degree path unless you are directly hindering your path to graduation. Most every liberal arts institution force students into taking an array of differing classes through area requirements. This is somewhat different than professional, vocational, or, to a lesser degree, technical schools which all strongly emphasize specialization of some sort.
The prerequisite requirements for dental school as a lump sum account for less than ~2 years worth of time. This leaves you with a lot of leftover time to do other things. Obviously, if you are science major, you will end up spending more time in related courses.
As for the DAT - many will debate this - but you really only need intro level coursework in chemistry, biology, and organic chemistry to do well on the science portion of the exam. And the rest of the test doesn't necessitate any college coursework.
As long as you are fulfilling requirements for your school, major, and dental school - take classes that interest you.
If you are a science major I would suggest taking some classes in personal finance or art to refine your motor skills. Most dental schools offer very little, if any, business education. Given that most graduates will end up in private practice, it will be in your best interest to build up a preemptive background in finance, management, or accounting - if even at the most basic of levels.
