Abutment

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Diagram of a bridge abutment

Abutment of a Nuremberg-Erfurt high-speed rail line

An abutment is an end support of a bridge superstructure.

Abutments are used for the following purposes:

• to transmit the reaction of superstructure to the foundations.
• to retain the earth filling.
• to connect the superstructure to the approach roads.

An abutment is also, generally, the point where two structures or objects meet.

Specifically, an abutment may be:

• the part of a structure that supports an arch.
• the tooth or teeth that support a fixed or removable bridge.
• the part of an implant that acts as an connection between the implant and the crown.

Abutment is also a term used by civil engineers in dam construction; moving water from a large reservoir to a channel such as a spillway, there are smooth transition walls at both sides named abutments which minimize the water's energy loss.

Ceramic Abutment connected to implant

Ceramic crown bonded to abutment

Prosthetic and Implant Dentistry

Abutment is also the term for a connecting element used to attach prosthetics to a dental implant that is Osseointegrated. These are susually called prosthetic implant abutments. These abutments can be made from a variety of materials, such as titanium, surgical stainless steel and gold. More modern abutments care now also made from zirconia, which is a white ceramic, to better complement the esthetics of a dental implant restoration. The two images to the right show a ceramic abutment and the ceramic crown bonded to it.

Prosthetic abutments are connected to the dental implants via a screw. This screw needs to be tightened to a predetermined torque, in order to avoid screw loosening during the masticatory cycle. Occlusal masitcatory forces can often create a counter-clockwise torque on the implant-abutment interface, encouraging the abutment screw to come loose. This can largely be prevented with proper screw design and torquing of the abutment.

The images to the right show how a cermic abutment can enhance a ceramic crown by giving it a more life-like appearance. Ceramic abutments have to be used with care,howver, since their compressive strength is nowhere near that of titanium, gold or other noble metals. Most clinicians feel more comfortable using a metal prosthetic abutment in the posterior molar areas, due to the increased masticatory forces present in these areas.

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