In vitro study of poly(lactic acid) pin degradation

Abstract

An evaluation was made of pins of poly(lactic acid), an absorbable polymer, produced both with very little crystallinity (PLLA-A) and with extensive crystallinity (PLLA-C). These polymer pins were submitted to in vitro tests to evaluate the effects of degradation on mechanical, thermal, and structural properties, as well as molar mass variation. The pins were molded and immersed in a phosphate buffer solution (pH=7.4) for 6 months. The results showed pins with greater crystallinity lost their mechanical properties more quickly, although an increase in the degree of crystallinity for both types of pins was observed over time. Structural analyses showed both superficial and internal erosion after two months of degradation. The greater retention of mechanical properties of the less-crystalline PLLA-A should prove useful in the production of implants where the stimulation of osteosynthesis is desired.