Torsion-axial force characteristics of SR-PLLA screws.
The torsion axial-force characteristics of biodegradable screws are central to their ability to generate interfragmentary compression when used as lag screws. The purpose of this investigation was to compare the torsion-axial force characteristics of prototype self-reinforced poly-L-lactide (SR-PLLA) screws with conventional titanium screws. Axial forces developed by incremental increases in the torque applied to the individual screws were measured in a test apparatus incorporating an Instron machine. For the SR-PLLA screws, the relationship between applied torque and axial force development was non-linear with a marked relaxation throughout the test range. The axial forces reached a maximum with increasing torque, after which failure of the screws occurred. The response curve for titanium screws of the same length demonstrated a steeper slope. No failures or force relaxation were observed with the titanium screws. The results of this investigation suggest that, at this time, the use of SR-PLLA screws for lag screw fixation should be restricted to low stress bearing areas.
Shetty
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V
Section of Oral and Maxillofacial Surgery, UCLA School of Dentistry, Los Angeles 90095-1668, USA.
Caputo
A A
AA
Kelso
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I
D001673:Biodegradation, Environmental; D001863:Bone Screws; D004867:Equipment Design; D004868:Equipment Failure; D008422:Materials Testing / Q000295:instrumentation; D011091:Polyesters / Q000737:chemistry; D013314:Stress, Mechanical; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry; D019415:Torque; D014102:Torsion Abnormality
D011091:Polyesters; C033616:poly(lactide); D014025:Titanium