Implant crowns can actually be designed in either of two ways. They can be made so that they directly screw into the implant, without an intermediary abutment, or they can be made so that they are cemented onto an intermediary abutment, as shown here.
The "screw-in" crowns actually have a "quasi-abutment" inside them, but the porcelain is fused onto the abutment. This has the big advantage of reducing the hardware count, but in my opinion has the disadvantage of a visible screw access hole. In the two-part system, the abutment hole is automatically covered up by the crown, which gets cemented over the abutment.
Additionally, if multiple units are splinted together into a bridge, it is almost impossible to produce a casting that fits passively (without strain) straight onto all of the implants which are anchors for the bridge. The abutments on the other hand, offer a little bit of "play" because of the inherent cement space they need to have.
A Dental Implant, as most patients understand it, typically consists of three parts:
- The Implant Fixture
- The (Prosthetic) Abutment
- The Crown (Cap)
On this page we will discuss the crown. The implant crown is the complementary part to the abutment. It is actually no different than a crown or cap for a regular tooth, where the custom-shaped implant abutment represents the "cut-down or prepared" natural tooth. Ceramic abutments are usually matched with all-ceramic crowns, in order to offer better esthetics. Most ceramic crowns have a very hard zirconia-type core, onto which porcelain is then baked. The core coping is often also made using CAD/CAM technology. Other materials for crowns include "porcelain-fused-to-metal" or even noble metal, such as gold.
