Effect of Thermo-mechanical Post-treatments on Injection-Molded PLGA 85:15 Maxillofacial Plates

Abstract

The effectiveness of an absorbable bone fixation plate is dependent, among other factors, on how well it fits the specific bone geometry of the patient. The glassy material should be heated above its glass transition temperature and shaped to its ideal geometry during the surgery. This may lead to alterations in the mechanical properties due to shape memory behavior, affecting the safety of the device. To investigate this behavior, we manufactured absorbable bone fixation plates by injection molding using the copolymer poly(lactic-co-glycolic acid) with lactide:glycolide molar fractions of 85:15 (PLGA 85:15) and characterized the influence of thermal–mechanical post-treatments. The shape memory was affected when the material was heated above its glass transition temperature, with the implant contracting in length by up to 17% and increasing in thickness by up to 25%. After the heat treatments, the stiffness decreased by almost 50% and the maximum stress under load by around 30%. A more ductile behavior accompanied these modifications in the implants. The results obtained provide a better understanding of PLGA 85:15 injection-molded bone plate characteristics and mechanical behavior.