I think you just have to call each school. I emailed the ADA, asking specifically if I needed to have my scores resent to the schools that had already received them last year. Their exact response was:
"Thank you for your recent inquiry regarding DAT scores. Please visit our website at www.ada.org to request to have additional scores sent. Go to Education and Testing, then to Dental Admission Test, then to Request Score Reports (electronic)."
Which is a great answer if I had inquired about how to request addition scores, but maybe the reason they did not answer my question directly was because they thought that it was inferred by their response.