In-Office Custom Abutments and Long-Term Provisionals

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 The milling abutment is placed into the soft-tissue model. Then the fixation screw is tightened to “finger tightness” so that the milling vibration does not cause the abutment to move on the model (Figures 4 to 6). The gross-reduction carbide (H847KRG.FG.018 [KOMET USA]) is used to reduce the occlusal surface. This is done so that the buccal and lingual edge of the abutment, which will become the cusp tips of the custom abutment, have sufficient clearance (2 mm is recommended), allowing the restoration be placed over it (Figure 7). When occlusal clearance is achieved, the gross-reduction football carbide (H379G.FG.023 [KOMET USA]) is then used to create buccal and lingual inclines on the occlusal surface (Figure 8). This is necessary so that the laboratory can create anatomy in the final crown and provide sufficient clearance. 

The tapered gross-reduction carbides (either the H856G.FG in 016/018 or H847KRG.FG in 016/018 [KOMET USA]) are used to reduce the interproximal to the level of the soft-tissue margin (Figure 9). This is also performed on the buccal and lingual surfaces (Figure 10). It is not necessary to perform a full reduction on these surfaces during this step, but it helps when you mark where the gingival margin is on the cast. The abutment(s) are marked with a permanent marker, indicating the buccal, and then the abutment is removed from the model. The soft-tissue material is removed from the cast, and the abutment is returned to the model, making sure it is positioned correctly with the buccal mark. The gross-reduction carbides are then used to reduce the circumferential surfaces, positioning the final margin approximately 0.5 mm apical to the mark created when the soft-tissue material was present. The benefit of working on the model is that it can be rotated in any direction and viewed from any angle so you can create the ideal preparation. Convergence of the preparation walls at approximately 6° should be the objective, giving the crown maximum retention to the abutment. 

The gross reduction carbides provide a rough surface, which will be difficult to capture in an impression because of surface tension between the impression material and the abutment’s surface. For this reason, the surface needs to have some finishing performed. Matching the gross-reduction carbides in the kit are titanium finishing carbides (H375R.FG.016/018, H336.FG.016/018, and H379.FG.023 [KOMET USA]). These are used to remove the rough marks on the titanium surface (Figure 11). 

The abutments are now ready for insertion into the patient (Figures 12 to 14). Provisional crowns may be fabricated on the abutments on the soft-tissue model, before the patient visit or on the soft-tissue model with the custom abutments on them. Both can be sent to the laboratory to have the final crowns created and delivered during the same appointment as the abutments. The impression heads and analog can be recycled, using them for subsequent patients after proper sterilization.