i believe every school will notify their first acceptances on Dec 1st (to answer above question), i haven't heard of any schools who does not give their acceptances out on dec 1.
Although some schools will make decision of your acceptance on the day of your interview after each interview group (e.g. Louisville) or they will meet during certain ADCOM meetings prior to Dec 1st. to make decisions of students from several interview groups (e.g. OU meets on Nov 20, if i remember correctly, to make all the decisions of their out-of-state acceptances and they will not make any more acceptances after that. instead they will fill any open spots with more in-state students).
to answer OP's question, each school will use different systems (email, snail-mail. personal call from office/dean) and this can be asked and answered during your interview or if you already had your interview, you can call and ask the school.
I believe, some schools will notify on midnight where they set up automatic email system (Louisville said this during interview that they do this but one year their system went down and ppl freaked out, so they told us not to stay up until midnight to check our emails) whereas some schools will send out acceptances when they get to work in the morning.
Best would be either ask current dental students, look up previous Dec 1st. posts where accepted students start "official XXX school class of XXX" and see how they were notified (there are tons of these posts every year for almost every school), or to just call them and ask.
hope this helps a little
