Abutment

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For the technical mathematical term, see Spectral sequence.

For the property law term, see abutter.

Diagram of a bridge abutment

Modern bridge abutments on Haikou Century Bridge

An abutment is, 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.

[edit] Bridge Abutments

An abutment is an end support of a bridge superstructure.

Abutments are used for the following purposes:

to transmit the loads of from the superstructure to the foundations.
support the bearing devices.
support the backwalls.

There are different types of abutments including:

Footing-Type Abutments - each has a footing, sill and end dam, 25-30 foot spans
Pile Abutments - consist of steel or timber and can support spans of any length
Concrete Abutments - the most permanent type, and can span any length with a max height of 20 ft

Ceramic Abutment connected to implant

[edit] Other Civil Engineering Applications of Abutments

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 crown bonded to abutment

[edit] Abutments in 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 usually 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 are now also made from zirconia, which is a white ceramic, to better complement the aesthetics 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 ceramic abutment can enhance a ceramic crown by giving it a more life-like appearance. Ceramic abutments have to be used with care, however, 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.