Effect of moisture and aging on gutta-percha.

The purpose of this article was to study the plasticizing effect of controlled levels of different humidities on native and commercial gutta-percha samples. It was expected that the results might provide the practicing endodontist with invaluable insight into the mechanical properties of commercial gutta-percha cones (i.e. retrievability, malleability, flexibility, torsional, and bending ability). The "conditioning" of the gutta-percha samples depended greatly on the percentage of compatible and incompatible substances. Mixtures of native gutta-percha with compatible substances (e.g. wax) showed greater elongation, tensile strength, and number of rotations but lower deformation angle than mixtures of native gutta-percha with incompatible substances (e.g. salts, metal oxides). The observed lower values for tensile strength and torsional strain and higher value for elongation and number of rotations for wet samples compared with the dry ones were attributed to the plasticizing effect on gutta-percha of the insertions of water molecules in the polymer chains.