Many of us love the screwmentation procedure for implant supported crowns due to the ease of adjustment and the retrievablility. There can be a problem with the procedure that I've previously shown. Because implant abutments are round and we must provide room for cement, most crowns will rotate ever so slightly on the abutment. This is especially true for zirconia crowns. If you bond the crown to the abutment outside the mouth, as I've previously shown, it's possible to get the crown slightly rotated on the abutment, and the bonded unit will not fit back on the implant. Ask me how I know! My good friend Alan Wolfson (AlanW) told me about this last year, but since I have so much crap after my name I didn't listen to him. Now I know so I'm telling you. After attaching the abutment to the implant, torqueing it down almost to final force, and adjusting the crown's proximal and occlusal contacts, bond or cement the crown to the abutment in the mouth. Allow plenty of time for the cement to cure as, unlike teeth, abutments are cold so the cements set slower. Then remove the bonded unit, clean off the excess, and proceed to final torque and filling the screw access.
So an improved procedure, at least for me. Thanks to Alan for the help. Bonding it clinically prevents getting the crown slightly out of alignment on the implant. If that happens then you have to send it back to the lab and they put it in a low temp oven to break down the cement. Then you get to start over. Hope this helps.