Test methodology for characterizing in vitro biodegradation

Abstract

—In this paper mechanical tests for the characterization of the time-dependent behaviour of absorbable osteosynthetic materials are described. The tensile test is performed according to International Standard Organization (ISO) 3268/1978 and provides Young's modulus, tensile strength, elongation at tensile strength, and rupture force. The bending test is performed according to ISO 178/1975 and gives the flexural stress at various deflections, the force and deflection at break and the initial bending modulus. The torsional test is carried out according to ISO 458-1 and gives torsional load. The bending and torsional stress relaxation are measured. Relaxation modulus and the creep compliance are then determined. The parameters to be recorded in a cyclic bending test include the number of cycles or, in the case of sample survival, the remaining force at break at a bending test. The cyclic torsion test is carried out according to ISO 537/1989. The parameters to be recorded are the number of cycles or, in case of sample survival, the remaining force at a torsional test at 45 deg. Simulation tests provide a comparative assessment of the degradation phenomena under cyclic mechanical loading in bending or in torsion at elevated temperatures.

Keywords:

• Osteosynthetic bioabsorbable materials
• biodegradation
• in vitro test methodology
• mechanical tests