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Rod contouring with French bender reduced stiffness and yield strength
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Rod contouring with the use of a French bender reduced rod stiffness and rod yield strength in all types of rods, according to researchers’ findings.
The researchers analyzed the effects of rod contouring on rod strength and stiffness through a three-point bending test, during which, an 18-cm rod was loaded with a load applicator at a rate of 10 mm per minute. The researchers assessed rod diameters of 5.5 mm, 6 mm and 6.35 mm and two different material types (titanium alloy and cobalt-chromium [CoCr] alloy). Additionally, four different rod curvatures were evaluated: a no-preparation rod of 0° acting as the control, a 0° rod bent at one point to make 10° tangential angles and then bent back from the opposite side, a bent rod with 20° tangential angles, and a 40° bent rod. All of the rods were bent using a French bender.
After bending, the yield strength decreased depending on the degree of bend, with the 0° bend showing a 74.5% reduction, the 20° reducing by 54.1% and the 40° reducing by 50.6%. The stiffness also reduced more with a higher degree of bend, according to the reseachers.
The researchers concluded the 6-mm CoCr rod showed the highest reduction force, and that the results from the study may influence the selection of rod material and diameter. – by Robert Linnehan
Disclosure: The researchers report no relevant financial disclosures.
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