In the Spear Digest article “Dark Tissue Around Implants?,” I discussed the treatment for the patient seen in Figure 1, who didn’t like the metal showing on her implant crown and the dark color of the surrounding tissue.
The treatment plan was to redo the implant restorations on #11 and #12. In addition to choosing a more esthetic custom abutment on #11, a facial connective tissue graft was also planned to increase the thickness of the soft tissue. Knowing the patient's chief concern upon initial presentation was the discoloration of the tissue, I wanted to make sure to choose something more esthetic than a metal abutment.
When filling out the prescription, I decided to have the technician fabricate a custom zirconia abutment. However, was this the correct solution? Who should choose the implant abutment — the dentist or the technician?
Typically, the dentist chooses the implant abutment. The decision is obvious if the dentist is the technician or the dentist plans to mill a CAD/CAM hybrid abutment in their own office. But even if the dentist is working with a lab technician, isn’t it generally the dentist who picks the abutment, since it is a box on the lab script that must be filled out when sending the case?
The difficulty of having the decision of abutment selection rest solely on the clinician is that quite often the clinician doesn’t understand some of the decision parameters that must be considered. For instance:
- How does the angulation of the implant affect the potential thickness of the axial walls?
- How thick does the zirconia need to be to have adequate strength?
Often, it is not until the technician has poured the model and either did a diagnostic wax-up or digitally designed the abutment/crown, that the proper implant abutment can be selected. (Fig. 2)
In this clinical example, I received a phone call from the technician informing me that if I truly wanted a custom zirconia abutment, there would be some structural issues. The reason was that given the angulation of the implant, the axial walls on the distal and palatal of the abutment were going to end up extremely thin. (Fig. 3)
Had the technician not passed along this crucial piece of information and instead just went ahead and followed the lab script, the patient would have ended up with a structurally weak abutment — and I would possibly end up seeing a fractured abutment down the road.
In speaking with the technician, we decided to use a custom metal abutment for strength but have ceramic baked on the subgingival cervical area so as not to negatively influence the esthetics of the tissue.
The abutment design in Figure 4, is referred to as a custom UCLA-metal ceramic abutment. In my practice, we often fall back on this abutment design due to implant position/type to provide predictability with bothstrength and esthetics. (Fig. 5)
Unfortunately in this situation, the lack of room also meant the definitive restoration had to be metal-ceramic (the restoration on #12 was designed as a screw-retained metal-ceramic crown). Even with this material selection, the outcome is nearly indistinguishable from the natural teeth, resulting in a very satisfied patient. (Fig. 6)
The take-home message is that the decision on the definitive abutment should be a collaboration between the dentist and the technician. It is only through this interdisciplinary type of interaction we can account for some of the nuances that arise in these types of situations.
The responsibility of the dentist is to inform the technician of what is needed, and the technician can then propose what options are available.
Greggory Kinzer, D.D.S., M.S.D., is a member of Spear Resident Faculty.