Adding a distinct second bend in the key shaft brought the bolster (fulcrum) in line with the middle of the handle and the axis of motion perpendicular to the tooth being extracted. In addition, a double bend shaft cleared anterior teeth more readily, making posterior tooth extractions less damaging.
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This shaft modification, introduced in 1795, resulted in this key of “Improved Construction.”
Courtesy of Martino Publishing, Eastford, CT— Colyer, 2006
The late 1700s ‘improved’ key (A147.168) shown here has a double-bend shaft,…
University of the Pacific Permanent Collection, Donor: Maurice J Owens, DDS
a carved ebony handle with cross-hatched design and waisted ends,…
a pear-shaped bolster, and…
a double-notched claw edge attached to the shaft head by a screw pin.