Seamless CEREC fits are a significant reflection from an accurate/technique oriented optical impression. Here is the deal,

1.  No pitching and rolling over preparations

2.  Take the least amount of overlaping optical captures to create an virtual die

3.  When rolling to the buccal for the buccal bite, do not roll over prep(s) or proximal contact(s) next to the preparation(s) See CEREC Liftoff Chapter 3 for further review.