- 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.
- 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:
- Dental GP usually exists in a beta semicrystalline state.
- Dental compounds of GP had 2 crystalline phase transformations when heated from room temperature to 100° C
- The lower, beta to alpha transformation took place between 42O C. and 49O C.
- The higher, alpha to amorphous change occurred between 53O C. and 59O C
- Transformation temperatures for the refined, uncompounded dental materials occurred within the same limits.
These phase transition temperatures are directly related to and responsible for the volumetric behavior of gutta-percha.