Just received this great question in my inbox. In short, yes you can, but are you sure you want to?
There are no rules against reusing the same letter writers or even the same letter of recommendations (with updated dates of course). However, if one did not have success last cycle, then it’s time to take a hard look at every aspect of one’s application and reflect on how one can be stronger for next time. The letters are a part of this process.
If you feel your letter writers did not know you as well and therefore couldn’t produce as enthusiastic of content, then it’s important to strategize: 1) You can pick new potential letter writers NOW and start to build those relationships. 2) If you intend to stay with the original letter writers, you should stay in touch, let them know of the outcome of the last cycle and of your intent to apply again. As the upcoming cycle opens in about 4-5 months, provide them with new information to make the letter even stronger than before. The bottom line is, LoRs for reapplicants should definitely touch on your commitment to dentistry and how impressed they are with what you’ve done in the gap year.