Synergic action of aging and moisture on native and different grades of commercial gutta-percha (trans-polyisoprene)

The aim of this paper was to study the plasticizing effect of subjecting native/commercial gutta-percha samples to controlled levels of different humidities. It was expected that this study would provide the practicing endodontist with invaluable insight into the mechanical properties of commercial gutta-percha cones (i.e., retrievability, malleability, flexibility, and torsional and bending ability). The “conditioning” of the gutta-percha samples depended greatly on the percentage of compatible/incompatible substances. The mixtures of native gutta-percha with compatible (i.e., wax) showed greater elongation, tensile strength, and number of rotations, but lower deformation angle than the mixtures of native gutta-percha with incompatible substances (i.e., salts, metal oxides). The observed lower values for tensile strength and torsional strain, relative energy to break, and the Young's modulus and the higher values for elongation and number of rotations for wet samples compared to the dry ones were attributed to the plasticizing effect of gutta-percha due to the insertion of water molecules in the polymer chains. © 1993 John Wiley & Sons, Inc.