Department of Endodontics, Fluminense Federal University, Niterói, Rio de Janeiro, Brazil.
Department of Dentistry II, Federal University of Maranhão, São Luís, Maranhão, Brazil.
Int Endod J. 2020 Nov;53(11):1506-1515. doi: 10.1111/iej.13370. Epub 2020 Sep 24.
To investigate a potential cause-effect relationship between dentinal microcracks and fracture resistance of mandibular incisors that had not been endodontically treated.
Sixty mandibular incisors with circular-shaped canals were selected based on micro-computed tomographic scans to create a homogeneous sample. The cross-sectional images of the specimens were screened to identify and quantify the presence of dentinal microcracks. Then, teeth were embedded in polystyrene resin and subjected to axial compressive loading using a universal testing machine. After fracture, the roots were re-scanned and fractography analysis was performed by inspection of 3D models to verify crack propagation. Spearman's rank correlation was used to assess the correlation between the number of microcracks and force required to fracture.
Dentinal microcracks were detected in 79% of the specimens (n = 44). The incidence of microcracks varied between teeth from 6% to 42% of the total slices per sample (average of 14 ± 17%). The number of microcracks per sample varied from 0 to 1605, with an average of 412 ± 484 (median = 221 and IQR 25% = 15/75% = 658). The load at failure values varied from 227 to 924 N, with an average of 560.3 ± 168.1 N (median = 561 and IQR 25% = 458/75% = 694). The Spearman correlation coefficient (rho) equalled 0.065.
There was no cause-effect relationship between the number of dentinal microcracks and the fracture resistance of nonendodontically treated mandibular incisors. The presence and quantity of microcracks did not make these roots more prone to fracture.
研究未经根管治疗的下颌切牙牙本质微裂纹与抗折能力之间是否存在潜在的因果关系。
根据微计算机断层扫描，选择 60 颗具有圆形根管的下颌切牙，以创建同质样本。对标本的横截面图像进行筛选，以识别和量化牙本质微裂纹的存在。然后，将牙齿嵌入聚苯乙烯树脂中，并使用万能试验机进行轴向压缩加载。断裂后，重新扫描牙根，并通过 3D 模型检查进行断口分析，以验证裂纹扩展。采用 Spearman 秩相关评估微裂纹数量与断裂所需力之间的相关性。
在 79%的标本（n=44）中检测到牙本质微裂纹。微裂纹的发生率在牙齿之间变化，每个样本的总切片中有 6%至 42%的牙齿存在微裂纹（平均 14±17%）。每个样本的微裂纹数量从 0 到 1605 不等，平均 412±484（中位数为 221，IQR 25%=15/75%=658）。断裂时的载荷值从 227 到 924N 不等，平均 560.3±168.1N（中位数为 561，IQR 25%=458/75%=694）。Spearman 相关系数（rho）为 0.065。
下颌切牙未经根管治疗的牙本质微裂纹数量与抗折能力之间无因果关系。微裂纹的存在和数量并未使这些牙根更容易发生断裂。
