Hsu Yung-Hao, Wang Hsin-Hui, Shen Yung-Kang, Gutmann James L, Hsieh Sung-Chih
School of Dentistry, College of Oral Medicine, Taipei Medical University, Taipei, Taiwan.
Department of Dentistry, Taipei Municipal Wan-Fang Hospital, Taipei, Taiwan.
J Dent Sci. 2020 Mar;15(1):28-33. doi: 10.1016/j.jds.2019.10.002. Epub 2019 Dec 24.
BACKGROUND/PURPOSE: 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.
背景/目的：在临床操作中，普通型和柔软型回填牙胶在质地和操作手感上的质性差异很容易辨别。本研究旨在调查和比较这两种牙胶材料的热行为和物理性能。
通过能量色散X射线光谱法检测普通型和柔软型牙胶尖充填器颗粒的化学成分。使用差示扫描量热仪评估颗粒在加热和冷却过程中的热行为。最后，使用模块化紧凑型流变仪评估两种材料在冷却过程中的粘弹性性能。
柔软型牙胶中锌的原子百分比高于普通型材料。此外，柔软型牙胶在冷却过程中出现放热峰，而普通型牙胶则没有。两种材料在冷却时表现出不同的粘弹性行为。特别是，在温度低于80°C时，柔软型牙胶的损耗因子变化率大于普通型牙胶。
柔软型牙胶在冷却过程中发生了显著的结晶，因此表现出明显的体积收缩。此外，柔软型牙胶在冷却时的粘弹性变化率比普通型牙胶更大，并且物理稳定性较差。因此，在回填过程中，随着时间的推移，柔软型牙胶必须比普通型牙胶更频繁地压实，以确保相同的根管充填质量。
