Part II of the Dental Boards means absolutely ZERO and here's why:
Typically, an applicant will submit their PASS application in June - September. For OMFS, interviews are anywhere from October - December and Match Day is at the end of January.
So if you are so lucky to receive interview invitations and go to interviews, it would be before New Years, usually 4th year dental student don't take the Part II until December or after New Years.
It is highly recommended that you don't take the Part II until you've completed all your OMFS interviews because in that way, you'll have one less item for them to judge your application. Personally, I took the Part II at the end of February AFTER Match Day. My philosophy was, if I matched, then I'll just wing it (aim to just pass), if I didn't match, then I'll study my ass off for Part II (aim for at least a 90).
I matched on Match Day, so I "winged" the Part II and got a phat 80 (studying only 4 days hardcore, didn't even finish the dental decks)!
On the flip side, if you didn't match on Match Day, then you'll want to do well so when you apply again next cycle, your Part II score will be judged with the rest of your application.
Bottom line:
1) if you're applying for Ortho or OMFS, don't take Part II until after Match Day
2) pray to god that you'll match on Match Day
3) if matched, then "wing" the Part II (aim to just pass)
4) if not matched, then you'll have to study your @ss off for the Part II to get a good score