Adjunct Professor, School of Dentistry, Autonomous University of Santo Domingo, Santo Domingo, Dominican Republic.
Research Associate, Department of Bioscience Research, College of Dentistry, University of Tennessee Health Science Center, Memphis, Tenn.
J Prosthet Dent. 2018 Mar;119(3):390-396. doi: 10.1016/j.prosdent.2017.05.007. Epub 2017 Jul 27.
Limited information is available on the effect of an incomplete ferrule because of the varying residual axial wall heights and the volume of residual tooth structure on the fracture resistance of endodontically treated and restored maxillary incisors.
The purpose of this in vitro investigation was to examine the effect of varying residual axial wall heights, residual coronal tooth structure, and the absence of 1 proximal axial wall on the fracture resistance and failure mode of endodontically treated teeth restored with metal posts.
Sixty intact human maxillary central incisors were divided into 6 groups (n=10): no ferrule (NF), 2-mm complete ferrule (CF2), 2-mm (IF2), 3-mm (IF3), and 4-mm (IF4) incomplete ferrules missing a single interproximal wall, and a control group that had a 6-mm incomplete ferrule (IF6). Cast metal post-and-cores were placed in all experimental specimens except for controls. Control specimens received 1 interproximal cavity preparation extending to the root canal access and a composite resin restoration. Complete metal crowns were then cemented on all specimens. Completed specimens were subjected to thermocycling (6000 cycles, 5°C/55°C) followed by the immediate testing of fracture resistance. Failed specimens were sectioned buccolingually and evaluated to identify the failure mode. The data were analyzed with an analysis of variance (ANOVA) and the Student-Newman-Keuls multiple comparison test (α=.05).
An incomplete ferrule (IF2) with 1 interproximal wall missing had significantly reduced fracture resistance (697 N) compared with a complete ferrule (932 N). An increase of 3 to 4 mm of remaining wall height improved fracture resistance, from 844 N (IF3) to 853 N (IF4). Partial decementation was noticed in 8 NF and 5 IF2 specimens. IF3 and IF4 had no decementations. Radicular fractures and cracks (catastrophic failure) were observed in all IF2, IF3, and IF4, 9 CF2, and 6 NF specimens. In 7 specimens without posts (IF6, control), composite resin foundation and/or coronal dentin fracture were observed and the failure was considered repairable.
The results of this in vitro study indicated that specimens with a 2-mm ferrule of uniform height were more resistant to fracture than specimens with a 2-mm ferrule and 1 missing interproximal wall. An increased wall height of 3 or 4 mm was associated with a significant increase in fracture resistance and can compensate for the missing interproximal wall.
由于剩余轴向壁高度和剩余牙体结构的体积不同，有关不完全金属全冠对根管治疗和修复后的上颌切牙抗折能力影响的信息有限。
本体外研究的目的是检查不同剩余轴向壁高度、剩余冠部牙体结构以及单个近中轴壁缺失对用金属桩修复的根管治疗牙抗折能力和失败模式的影响。
将 60 颗完整的人上颌中切牙分为 6 组（n=10）：无金属全冠（NF）、2mm 完整金属全冠（CF2）、2mm （IF2）、3mm （IF3）和 4mm （IF4）不完全金属全冠缺失单个近中轴壁，以及一个有 6mm 不完全金属全冠（IF6）的对照组。除对照组外，所有实验标本均放置铸造金属桩核。对照组接受 1 个邻面洞制备，延伸至根管入口，并用复合树脂修复。然后将所有标本用全金属冠粘固。完成的标本进行热循环（6000 次循环，5°C/55°C），然后立即进行抗折能力测试。失败的标本进行颊舌向剖面并进行评估，以确定失败模式。使用方差分析（ANOVA）和学生-纽曼-凯斯（Student-Newman-Keuls）多重比较检验（α=.05）对数据进行分析。
与完整金属全冠（932N）相比，缺失 1 个邻面的 1 个近中轴壁的不完全金属全冠（IF2）的抗折能力显著降低（697N）。剩余壁高度增加 3 至 4mm 可提高抗折能力，从 844N（IF3）增加到 853N（IF4）。8 个 NF 和 5 个 IF2 标本中注意到部分脱粘。IF3 和 IF4 没有脱粘。所有 IF2、IF3 和 IF4、9 个 CF2 和 6 个 NF 标本均观察到根折和裂缝（灾难性失败）。7 个无桩（IF6、对照组）标本观察到复合树脂基底和/或冠部牙本质断裂，认为该失败可修复。
本体外研究结果表明，具有均匀高度 2mm 金属全冠的标本比具有 2mm 金属全冠和 1 个缺失邻面的标本更能抵抗折裂。壁高度增加 3 或 4mm 与抗折能力的显著增加相关，并可补偿缺失的邻面。
