Friedman C M, Sandrik J L, Heuer M A, Rapp G W
J Dent Res. 1975 Sep-Oct;54(5):921-5. doi: 10.1177/00220345750540052901.
Gutta-percha endodontic filling points were found to contain approximately 20% gutta-percha (matrix), 66% zinc oxide (filler), 11% heavy metal sulfates (radiopacifier), and 3% waxes and/or resins (plasticizer). The mechanical properties were indicative of a partially crystalline viscoelastic polymeric material. They were found to obey Hooke's law and displayed a prominent upper and lower yield point when stressed beyond the proportional limit. The essential differences in mechanical properties of individual brands were found to be a function of the gutta-percha and zinc oxide concentration.
牙胶尖根管充填尖被发现含有约20%的牙胶（基质）、66%的氧化锌（填料）、11%的重金属硫酸盐（射线阻射剂）以及3%的蜡和/或树脂（增塑剂）。其机械性能表明它是一种部分结晶的粘弹性聚合材料。研究发现它们符合胡克定律，并且在应力超过比例极限时会呈现出明显的上屈服点和下屈服点。各品牌机械性能的本质差异被发现是牙胶和氧化锌浓度的函数。
