Department of Dentistry, Pontifical Catholic University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil.
School of Medicine, University of Buenos Aires, Buenos Aires, Argentina.
J Endod. 2021 Jul;47(7):1157-1165. doi: 10.1016/j.joen.2021.04.016. Epub 2021 Apr 24.
The present study aimed to describe an in vitro study model to investigate root surface strain (RSS) and its correlation with the initiation/propagation of microcracks during different endodontic procedures.
Four lower human incisors extracted microcrack free were selected by micro-computed tomographic imaging. Two strain gauges were bonded to the root surface of each incisor. Then, the teeth were prepared to reproduce the periodontal ligament artificially. The gauges were attached to a data acquisition system. The RSS was recorded during the entire endodontic procedure, which consisted of accessing the endodontic cavity, cleaning, shaping preparation with an Mtwo rotary system (VDW, Munich, Germany), and filling with a standardized technique. Each incisor was submitted to a different retreatment protocol and supplementary cleaning method as follows: (1) Reciproc (RC, VDW) + Flatsonic (FS; Helse, Santa Rosa de Viterbo, Brazil), (2) RC + XP-endo Finisher (XPF; FKG Dentaire, La Chaux-de-Fonds, Switzerland), (3) Mtwo retreatment (MR) + FS, and (4) MR + XPF. Finally, the teeth were rescanned to establish the postoperative microcrack formation by 2 well-trained and blinded examiners.
The maximum and minimum RSS values were -120 and 510 microstrains, respectively, for all of the files. RC showed the highest RSS values during endodontic retreatment compared with MR. FS demonstrated a higher variation between the minimum and maximum RSS than XPF. No microcracks were observed in the specimens.
This preliminary study proposed an experimental model that would combine 2 methods to evaluate the effects of endodontic systems on dentin. Although strain gauges would provide data on the stresses created, the pre- and postoperative evaluation of micro-computed tomographic images would enable microcrack formation to be determined.
本研究旨在描述一种体外研究模型，以研究不同根管治疗过程中根面应变（RSS）及其与微裂纹起始/扩展的相关性。
通过微计算机断层扫描成像选择 4 颗无微裂纹的下颌切牙。将两个应变片粘接到每个切牙的根面。然后，将牙齿制备以人工再现牙周膜。在整个根管治疗过程中记录 RSS，该过程包括进入牙髓腔、清洁、用 Mtwo 旋转系统（VDW，慕尼黑，德国）进行形状准备以及采用标准化技术进行填充。每颗牙齿都采用不同的再治疗方案和补充清洁方法进行处理，具体如下：（1）Reciproc（RC，VDW）+Flatsonic（FS；Helse，Santa Rosa de Viterbo，巴西），（2）RC+XP-endo Finisher（XPF；FKG Dentaire，La Chaux-de-Fonds，瑞士），（3）Mtwo 再治疗（MR）+FS，和（4）MR+XPF。最后，由 2 名经过良好培训且盲法的检查者对牙齿进行重新扫描，以确定术后微裂纹的形成情况。
所有锉的最大和最小 RSS 值分别为-120 和 510 微应变。与 MR 相比，RC 在根管再治疗过程中显示出最高的 RSS 值。FS 显示的最小和最大 RSS 值之间的变化比 XPF 更大。在标本中未观察到微裂纹。
本初步研究提出了一种实验模型，该模型将结合 2 种方法来评估根管系统对牙本质的影响。尽管应变片可以提供关于产生的应力的数据，但在术前和术后进行微计算机断层扫描图像评估可以确定微裂纹的形成。
