"I believe I could improve my written communication skills as I tend to be longer-winded than I would like to be at times in written communications. I enrolled in a week-long workshop this summer, intending to become a more succinct written communicator. I hope to gain skills in this workshop that I can continue to utilize during my time as a dental student and in practice down the road."

As you answer a question like this, you want to ideally pick a weakness that is not a core skill for your success as a dentistry student. You can be candid in your answer, recognizing that you aren't great at something and acknowledging your need to improve. Your interviewers know that a candidate who admits no weakness is either not self-aware or trying to hide something. Be sure to have an action plan to improve this weakness as a dental student.