The thermomechanical properties of gutta-percha. I. The compressibility of gutta-percha.

Sample wafers of compounded dental gutta-percha and uncompounded dental-grade gutta-percha were compression tested to 20,000 pounds in uniaxial and triaxial systerns. Unrestrained flow in the uniaxial series prevented development of stress levels sufficient to produce molecular compression. Negligible molecular compression did occur in the triaxial series but only above a stress level of approximately 2,000 p.s.i. Below this level there was a reduction in volume due to consolidation and collapse of voids. Compressibility values for compounded dental gutta-percha proved to be less than that of water, considered for all practical purposes to be incompressible. Gutta-percha material undergoes compaction and not true compression during its clinical application; therefore, no molecular “spring-back” can be expected to assist in the seal at the dentin-gutta-percha interface. Reduction in apparent volume is due to consolidation and collapse of voids.