An implant abutment provides supports for the definitive intra-oral restoration(s), and the choice is dictated by the type of prosthesis (fixed or removable), location in the mouth, and the material for optimal anterior aesthetic and resisting both external (functional and parafunctional) and internal (preload) forces.
Implant abutments are available in two varieties:
- One-component – combining the abutment and fixture as an all-in-one implant;
- Two-component – separate abutment that is connected onto the fixture head with either a retaining screw (usually at a torque of 20 N cm), or cemented into place. To prevent abutment screw loosening, some screws are gold-plated for improved retention by creating a bond equivalent to a ‘cold weld’. The two-component is the most popular and universal system, offering versatility for fixture angulation and numerous types of abutment to suit different definitive prostheses. The following discussion is therefore limited to this variety.
The market is awash with more than twenty different types of implant–abutment connections. It is important that the connection offers optimal mechanical stability, strength, fatigue resistance, anti-rotation, prevent microleakage and screw loosening and provide a hermetic seal (minimum micro-gap, i.e. butt-joint gap between the abutment and the implant fixture of approximately 2–6 µm). Currently, no connection (or interface) prevents bacterial penetration into the micro-gap. In addition, the clinically acceptable vertical and horizontal discrepancies (marginal fit) between the abutment and fixture should be similar to that of the marginal discrepancies between a natural tooth abutment and artificial restoration (approximately +/− 50 µm). Some popular implant/abutment interfaces include:
- External connection, e.g. external hexagon (hex), which was the original connectio/>