AADSAS will also request that you send them official transcripts from every university that you have attended. I suggest that, if it is possible, you should send those transcripts through a service that gives you some tracking information so that you will know that they were delivered to the AADSAS.
This may or may not be possible, depending on the institution you attend(ed). Official transcripts are usually not released to the student, but rather sent directly to the requestor, taking away any possibility that the student could tamper with the information in the transcript. Stop by the office where you request transcripts and ask if you can supply them with a prepaid envelope that is addressed to the AADSAS. Most offices will be happy to do this, particularly if you let them know of the importance of being early when applying for dental school.
If they are willing to send them in your envelope, the extra 15 dollars spent for a FedEx delivery will give you some peace of mind.