Obermayr G, Walton R E, Leary J M, Krell K V
Department of Endodontics, University of Iowa, College of Dentistry, Iowa City.
J Prosthet Dent. 1991 Aug;66(2):181-7. doi: 10.1016/s0022-3913(05)80045-9.
There are several speculated etiologies of vertical root fractures such as pressure exerted during post placement and excessive forces during lateral condensation. However, there are no reports comparing these two forces by use of the same measurement system. This study determined and compared on single-rooted teeth (1) the amount of strain to the root that occurs during obturation and post cementation and (2) the incidence of incomplete and complete vertical root fractures occurring during the aforementioned procedures. Canals of 32 extracted maxillary central incisors were step-back prepared. Teeth were randomly divided into negative and positive controls and experimental groups. The amount of root distortion was recorded with a strain gauge during each of the following procedures: (1) lateral condensation, and (2) lateral condensation plus cementation of a cast gold post. Relative deformations were compared statistically. Teeth were examined by transillumination and stereomicroscopy for incomplete and complete fractures and compared among groups. Data showed significantly more relative deformation with placement of a post and loading than with obturation alone. The accumulation of strain from both procedures did not significantly increase incidence of vertical root fractures. The results indicate that stresses from cementation of posts is more likely to cause relative deformation of roots.
垂直根折有多种推测的病因，如桩置入过程中施加的压力以及侧向加压时的过大力量。然而，尚无使用相同测量系统比较这两种力量的报告。本研究针对单根牙确定并比较了：（1）根管充填和桩黏固过程中牙根产生的应变大小，以及（2）上述操作过程中发生不完全和完全垂直根折的发生率。对32颗拔除的上颌中切牙进行逐步后退法预备根管。将牙齿随机分为阴性和阳性对照组以及实验组。在以下每个操作过程中用应变片记录牙根变形量：（1）侧向加压，以及（2）侧向加压加铸造金桩黏固。对相对变形进行统计学比较。通过透照法和体视显微镜检查牙齿有无不完全和完全根折，并在各组之间进行比较。数据显示，与单纯根管充填相比，桩置入和加载时的相对变形明显更多。这两个操作过程中应变的累积并未显著增加垂直根折的发生率。结果表明，桩黏固产生的应力更有可能导致牙根的相对变形。
