Thermal behavior and viscoelastic properties of gutta-percha used for back-filling the root canal

• Published in: Journal of dental sciences 2020-03, Vol.15 (1), p.28-33
• Main Authors: Hsu, Yung-Hao, Wang, Hsin-Hui, Shen, Yung-Kang, Gutmann, James L., Hsieh, Sung-Chih
• Format: Article
• Language: English
• Subjects: Differential scanning calorimetry; Gutta-percha; Original; Root canal obturation; Viscoelastic substances
• ISSN: 1991-7902; 2213-8862
• DOI: 10.1016/j.jds.2019.10.002

In clinical operations, qualitative differences in the texture and operational feeling of the regular type and soft type back-filled gutta-percha are readily discernible. This study aimed to investigate and compare the thermal behavior and physical properties of the two gutta-percha materials. The chemical compositions of regular and soft type Gutta-Percha Obturator® pellets were examined via energy dispersive X-ray spectroscopy. The thermal behaviors of the pellets during heating and cooling were evaluated using a differential scanning calorimeter. Finally, the viscoelastic properties of the two materials during cooling were assessed using a modular compact rheometer. The soft type gutta-percha contained a greater atomic percentage of zinc than the regular type material. In addition, the soft type gutta-percha exhibited exothermic peaks during cooling, whereas the regular type gutta-percha did not. The two materials exhibited different viscoelastic behaviors under cooling. In particular, the rate of change of the loss factor for the soft type gutta-percha was more than that of the regular type gutta-percha at temperature lower than 80°C. The soft type gutta-percha underwent significant crystallization during cooling, and therefore exhibited pronounced volume shrinkage. Furthermore, the soft type gutta-percha underwent a greater rate of change in viscoelasticity under cooling than the regular type gutta-percha, and exhibited poorer physical stability. Consequently, in the back-packing procedure, soft type gutta-percha must be compacted more often over time than regular type gutta-percha to ensure the same quality of root canal obturation.