The thermomechanical properties of gutta-percha III. Determination of phase transition temperatures for gutta-percha ​

By Schilder H, Goodman A, Aldrich W

Date: 05/1974
Journal: Oral Surg Oral Med Oral Pathol.

Summary:  ​

  • Purpose: to demonstrate the phase transformations which occur in the crystalline structure of the polymer during thermal manipulation and to determine the temperature at which they take place. ​
  • N= 21 materials were evaluated. ​

Materials/Methods: 

  • A broad range of gutta-percha materials was evaluated, representing several brands of compounded and uncompounded dental-GP. ​
  • Refined, synthetic, and crude specimens from nondental commercial sources were also tested for comparison.​
  • Samples of GP were subjected to analysis with a Perkin-Elmer differential scanning calorimeter, ​
  • Heating rate  of 10oC per minute was satisfactory.​  ​

Most highlighted Results:

  1. Dental GP usually exists in a beta semicrystalline state. ​
  2. Dental compounds of GP had 2 crystalline phase transformations when heated from room temperature to 100° C ​
  3. The lower, beta to alpha transformation took place between 42O C. and 49O C. ​
  4. The higher, alpha to amorphous change occurred between 53O C. and 59O C ​
  5. Transformation temperatures for the refined, uncompounded dental materials occurred within the same limits. ​

Clinical significance:​

These phase transition temperatures are directly related to and responsible for the volumetric behavior of gutta-percha. ​