Another piece of learning for me out of this week’s symposium was about the design of implant abutments in the esthetic zone. A common challenge with implant restorations is that the interface between the abutment and the crown is placed further apically then it should be. Our thinking behind this is to utilize the emergence profile of the crown to help develop and hold tissue form. The final pink esthetics are founded on the surgical outcome and developed and maintained by the abutment design. The tooth esthetics is controlled by the crown.
So when we think about the abutment developing and maintaining the pink esthetics what are the critical factors related to design. First and foremost convex shapes move tissue apically and concave shapes move the pink incisally. If we observe the difference in the free gingival margin between when only a healing cap is present and then to an abutment and crown, we will watch the free gingival margin move in an apical direction. The emergence profile of a healing cap is flat, and classically we create a convex shape int he abutment and the crown. Create a flat or concave shape to the abutment as it leaves the fixture, both facially and interproximally.
The research supports that the materials we want in contact with the junctional epithelium are titanium or zirconia. Gold, resin and traditional porcelain create a tissue reaction that can result in alteration of the osseous and gingival architecture. This limits us to two abutment materials. The abutment should be designed with a margin, just like a crown preparation. This margin should be ideally placed 1mm subgingival to the expected free gingival margin. This placement optimizes the esthetic result and allows appropriate cleaning of cement. When considering the interproximal soft tissue architecture, we expect to see the papilla in it’s final position 4mm coronal to the osseous crest. Therefore we can sound to bone and advise the lab to begin the contact point 4mm coronal to the osseous crest. therefore the abutment margin interproximally will be positioned 3mm from the osseous crest. To support the interdental soft tissue we want the interproximal wall of the abutment to be less than 2mm from the adjacent tooth. This interproximal surface also needs to have dimension in a buccal to lingual dimension, usually between 1.5 and 2mm.
I for one will plan moving forward for the abutment to develop and maintain the pink esthetics, and use the crown for the tooth esthetics.