depends on your intelligence and how well you can study and lab skill. I think 1 day of dental school material is almost equal to 1 week of undergrad load. (i.e. 1 quarter of biochemistry covers 1 year of undergrad biochem). Also, you better makes no mistake and perfect your lab skill such as waxing crown and set teeth on dentures (depends on school). almost everyday was a bit stressful because you are expected to do well in school, quiz after quiz, competency exam after competency exam . sure below 75% is failure. you also need to worry about finding patients for your clinic requirements, have your lab case ready for sign off and process...etc. all i can say is that a lot of crap you need manage and your significant other would have to be really supportive. also keep in mind that since admission standard is getting higher and higher, you are competing among many top tip students in class. There are no dumb people in class....well maybe 1 or 2 that you have no clue how they got in but they usually get drop out pretty quick. yes dental school will drop out students that cannot catch up or clearly not ready without hesitation.
I was struggling, i usually slept only 5-6 hours a day. i also study in weekends too but I will always make my Friday night a relax night and occasionally Saturday too. however, although i was at the lower end of rank of my class....my school prepared me well for board exam and it only took me less than 8 days to prepare and pass.