I think the earliest you can apply is June 1st (although some will say earlier), but the application is available for you to fill out around mid-May. And do yourself a favor by submitting your application ON June 1st. Then it takes about a month or so for AADSAS to get your application mailed out to the dental schools you designated, so try to have your LORs in the mail to AADSAS by the end of May. Good luck!!