Cantilever Extension
An unsupported distal segment of a fixed implant prosthesis that extends beyond the most posteriorly positioned implant, subject to increased bending forces.
Full Definition
A cantilever extension (also called a cantilever pontic or distal cantilever) is the portion of a fixed implant-supported prosthesis that projects distally beyond the last supporting implant. Because it lacks terminal implant support, a cantilever extension creates a lever arm that amplifies occlusal forces and transmits bending moments to the implant–bone interface. The accepted maximum cantilever length is generally calculated as a function of the A-P spread and the number and distribution of supporting implants. Excessive cantilever extension is a recognised risk factor for mechanical complications, including screw fracture, framework fracture, and crestal bone loss. Editors should distinguish cantilever extension from pontic, which is an unsupported crown between two supported units.
Usage
Usage note: Distinguish 'cantilever extension' (unsupported terminal segment) from 'pontic' (an unsupported unit between two supported units). The biomechanical risk profile differs significantly.
In Context
- "The 18 mm cantilever extension was deemed excessive relative to the calculated A-P spread of 14 mm." — Treatment planning consultation note
- "Fracture of the titanium framework was attributed to a 22 mm cantilever extension in a bruxist patient." — Complication case report