Berry K A, Loushine R J, Primack P D, Runyan D A
U.S. Army Dental Activity, Fort Gordon, GA, USA.
J Endod. 1998 Nov;24(11):752-4. doi: 10.1016/S0099-2399(98)80167-2.
Placement of endodontic spreaders to within 1 to 2 mm of the root canal working length has been advocated for optimum gutta-percha obturation. Due to their stiffness, stainless-steel (SS) spreaders will often fail to achieve this position in curved canals. Newly marketed nickel-titanium (NiTi) spreaders may offer an advantage in this regard due to the increased flexibility of these instruments. Seventy mesial and distal mandibular molar canals were instrumented to a #35 master apical file size. Measurements of the canal curvature were made from preoperative radiographs. Canal curvature angles ranged from 0 to 51 degrees. The teeth were placed in a radiographic mount to ensure a constant focal length, and postoperative radiographs were exposed with comparably sized SS and NiTi spreaders inserted into each prepared canal. Measurements of spreader tip to apex distance were made with a micrometer to the nearest 0.02 mm on the radiographs. Using a t test for paired samples, it was shown that NiTi spreaders penetrated to a significantly greater depth than SS spreaders in curved canals (p < 0.001).
为实现最佳的牙胶充填效果，提倡将根管扩大器放置在距根管工作长度1至2毫米范围内。由于不锈钢（SS）扩大器的硬度，在弯曲根管中它们常常无法达到这一位置。新上市的镍钛（NiTi）扩大器可能在这方面具有优势，因为这些器械的柔韧性有所增加。对70个下颌磨牙的近中根管和远中根管进行预备，达到#35主尖锉尺寸。从术前X光片测量根管弯曲度。根管弯曲角度范围为0至51度。将牙齿放置在X光片定位架中以确保焦距恒定，在每个预备好的根管中插入尺寸相当的SS和NiTi扩大器后拍摄术后X光片。在X光片上用千分尺测量扩大器尖端到根尖的距离，精确到最接近的0.02毫米。使用配对样本t检验表明，在弯曲根管中，NiTi扩大器比SS扩大器穿透的深度明显更大（p < 0.001）。
