*Domingo Santos Pantaleón, DDS, MSD, PhD, professor (retired) of prosthodontics, School of Dentistry, Autonomous University of Santo Domingo, Santo Domingo, Dominican Republic.
Fabio M. Valenzuela, DDS, associate professor of prosthodontics, School of Dentistry, Autonomous University of Santo Domingo, Santo Domingo, Dominican Republic.
Oper Dent. 2021 Nov 1;46(6):669-679. doi: 10.2341/20-164-L.
To investigate the effect of a cervical cavity extending 1 mm apical to the cemento-enamel junction (CEJ) on fracture resistance and failure mode of maxillary central incisors that have been treated endodontically, present with complete and incomplete ferrules, and are restored with and without a fiber post.
50 intact human maxillary central incisors were divided into five groups (n=10): CG (control group) 6-mm fer-rule height, no cervical cavity, and without post; (CO) 6-mm ferrule height without post, with a cervical cavity (access to root canal and cervical cavity restored with composite resin), cervical cavity; and post with ferrule heights of 1 mm (CP1), 2 mm (CP2), and 6 mm (CP6) restored with fiberglass post and composite resin core. After complete metal crowns were cemented on all specimens, they were subjected to thermal cycling (6000 cycles, 5°C/55°C), followed by immediate testing of fracture resistance. After failure, the specimens were sectioned buccolingually to evaluate and identify the mode of failure. The data were analyzed with an analysis of variance (ANOVA) and the Student-Newman-Keuls multiple comparison tests (α =0.05).
A 1-mm ferrule height (CP1) fracture resistance was significantly lower (531±125 N) compared to the 6-mm ferrule height (CP6) (769±175 N) (p<0.05). With respect to the groups with similar residual dentin, with and without a cervical cavity, CG (667±119 N) and CO (668±119 N), the presence of a post (CP6) increased the resistance to fracture, although no statistically significant difference was demonstrated. Partial decementation was observed in all specimens of CG and CP6, in nine of CP1 and CP2, and in three in CO. Root fractures occurred in 23 specimens. The root surface was exposed 2 mm below the CEJ to simulate bone level. Propagation of subosseous cracks occurred in four specimens in CG and CP2, in seven specimens in CP6, in two specimens in CP1, and in six specimens in CO. All were considered catastrophic failures.
Within the limitations of this study it is suggested that, when restoring an endodontically treated maxillary central incisor that has a cervical lesion and needs to be restored with a complete crown, a fiber post is cemented to improve fracture resistance.
研究牙冠延长 1mm 对根管治疗后、有完整或不完整肩台、并使用纤维桩或不使用纤维桩修复的上颌中切牙抗折强度和破坏模式的影响。
将 50 颗完整的人上颌中切牙分为 5 组（n=10）：CG（对照组），6mm 肩台高度，无颈腔，无桩；（CO）无桩，有颈腔（进入根管和颈腔用复合树脂修复），颈腔；和纤维桩高度为 1mm（CP1）、2mm（CP2）和 6mm（CP6）的带桩修复，并用玻璃纤维桩和复合树脂核修复。所有标本均用全金属冠粘固后，进行热循环（6000 次，5°C/55°C），然后立即进行抗折强度测试。失效后，标本沿颊舌向进行剖切，以评估和确定失效模式。使用方差分析（ANOVA）和 Student-Newman-Keuls 多重比较检验（α=0.05）对数据进行分析。
颈腔高度 1mm（CP1）的抗折强度（531±125N）明显低于颈腔高度 6mm（CP6）（769±175N）（p<0.05）。对于具有相似剩余牙本质的组，有颈腔和无颈腔，CG（667±119N）和 CO（668±119N），使用桩（CP6）增加了抗折强度，尽管没有统计学意义。所有 CG 和 CP6 标本均观察到部分牙冠折，CP1 和 CP2 各 9 个标本，CO 各 3 个标本。23 个标本发生根折。将根面暴露在牙骨质界下 2mm 处模拟骨水平。CG 和 CP2 中有 4 个标本出现骨下裂纹扩展，CP6 中有 7 个标本，CP1 中有 2 个标本，CO 中有 6 个标本。所有这些都被认为是灾难性的失败。
在本研究的限制范围内，建议对于需要全冠修复的有颈病变并需要进行根管治疗的上颌中切牙，使用纤维桩可提高抗折强度。
