PART PREPARATION (screw retained) ZIRCONIA ABUTMENT

Before & after

In most situations a custom zirconia abutment needs to be made for a screw retained all ceramic restoration. Not all stock zirconia abutments (Biomet 3i) are suitable for overlaying bake on porcelain because the indexing feature is a prebonded metal piece. Others (Nobel Replace) have a metal indexing feature press fit in to the abutment, which needs to be removed after applying the veneering porcelain and before baking on the veneering porcelain.

Prepped abutment

For completeness sake we will describe the adjustment process to prepare a stock zirconia abutment for direct veneering with porcelain. In case a suitably dimensioned stock zirconia abutment without a metal indexing feature (BioHorizons) can be utilized, reduce the abutment height with a water cooled, high-speed hand piece and a diamond bur (Brasseler part # 2855.31.025) to create enough room for the veneering porcelain (1.5mm to 2mm). Use only light pressure to prevent overheating the abutment which might cause micro cracks.

Finished restoration

Next reduce the mesial and distal aspects of the abutment to allow for proper porcelain thickness. Looking down from the occlusal, check if the facial and lingual portion also need reduction to create enough room for the restorative material. Any part of the pre machined collar above the tissue needs to be rounded off and adjusted below the crest of the tissue.