On the perio part if they deny your patient selection you will fail on the spot.
On the restorative part if they deny both patients for one cavity type you'll fail. If you leave caries in the prep when you submit your final prep you'll fail. If you have an open contact or they can't thread floss through the contact on your final restoration you'll fail.
If you don't finish something in the time limit you fail.
There's other things they'll on-the-spot fail you for if you check the manual (you can find it on their website www.nerb.org) but those are definitely big ones to watch out for.
If you make it past the auto-fail steps you are likely to pass but they've definitely failed people who seemed to make it through unscathed... although not as often.
