PART PREPARATION (cementable) METAL SUBSTRUCTURE

Virgin abutment

Titanium abutments usually need some form of reduction in height, path of insertion and margin placement. If the stock abutment is pre machined with a sloping collar, position the abutment with the narrow part of collar were the tissue height is the thinnest. Screw down the abutment with a laboratory screw (do not use the final screw while working on the case) and lift up the soft tissue to verify the abutment is properly engaged and seated.

Height reduction

Reduce the abutment height with a heat less Mizzy wheel to create enough room for the metal coping and porcelain (2mm). Next reduce the mesial and distal aspects of the abutment with a joe dandy disc to allow for proper draw. Looking down from the occlusal, check if the facial and lingual portion also need reduction to create enough room for the restorative material.

Buccal reduction

Any part of the pre machined collar above the tissue needs to be adjusted down to the crest of the tissue. Mark the collar of the abutment with a sharpie marker on the facial aspect of the abutment and remove the abutment from the working model. Attach the abutment to a second analog for ease of handling and protection of the indexing feature. Reduce the collar with a Brasseler® carbide (order # 006617U0) where marked with the sharpie marker to the desired tissue depth without creating a undercut on the abutment. Cut antirotational grooves on the mesial and distal long axis of the abutment.

Anti rotation groove

Each dentist has different preferences how deep the margin should be placed below the tissue. Placement of the margin more than 1.5mm below the tissue will make it difficult for the dentist to clean excess cement from the sulcus at the time of delivery.

Ready for FGC

Reposition the abutment back on to the working model and double check for clearance, path of insertion and proper margin design with the soft tissue mulange in place. The abutment portion to which the crown will be cemented should not be shorter than 3mm. Mark the facial of the abutment with a round bur to ease proper positioning at the time of delivery by the dentist.