Mechanisms of vertical root fracture and clinical approach

从牙髓学、牙外科、正畸学和牙材学的角度对牙根垂直骨折进行了研究。应用光学相干断层扫描（OCT）诊断牙根断裂。探讨胶粘剂是否能预防离体牙根垂直断裂。根管充填后，用胶粘剂充填根管，根管垂直加载。观察牙根断裂情况，认为粘接剂不能预防牙根垂直断裂。对于垂直牙根骨折，临床建议采用树脂粘接的牙片再植来保护断裂的牙。本研究的目的是评估牙根断片再植的粘接材料对牙本质粘接长期耐久性的影响。在本研究中使用了三种牙本质粘接剂系统以及复合芯材料和三种mma基树脂胶结剂。从人类门牙上切下的牙根碎片用一种胶粘剂粘接，在水中浸泡一年，测量了微拉伸粘接强度。结果表明，黏合剂体系的选择对牙本质黏结的耐久性有一定的影响。采用人拔牙载荷试验、光弹性分析和有限元分析三种方法，对不同类型桩核冠根管治疗后的牙内应力分布进行评估。结果表明桩核结合和冠对防止根内应力集中起着重要的作用。对于具有高弹性模量的桩和核采用高弹性模量制作的冠，以及对于具有低弹性模量的桩和核采用低弹性模量制作的冠，可以防止应力集中。实验纤维增强聚合物根管点可提高根管垂直断裂的抵抗能力，尤其是根尖制备较大时。人工垂直断牙的裂缝长度随时间延长，但使用粘接剂根管封闭剂时，裂缝长度延长的比例较小。设计了一种施加根管壁载荷的垂直断裂模拟系统，但该系统对根管充填材料的影响不显著。纤维桩有望减少根管垂直断裂。因此，我们研究了纤维桩对根管空间中胶凝物聚合的影响。不同产品的聚合能力有显著差异。少

Vertical root fracture was investigated from the view of endodontics, operative dentistry, orthodontics and dental materials.Optical Coherent Tomography (OCT) was applied to diagnose root facture. It was investigated if adhesive sealer could prevent vertical root fracture in vitro. After root canal filling, roots with adhesive sealer, roots were loaded vertically. Root fracture was observed, and it was concluded that adhesive could not prevent vertical root fracture.For vertical root fracture, replantation of tooth fragments bonded with an adhesive resin cement isproposed as a clinical treatment to preserve the fractured tooth. The purpose of this study was to evaluate the effect of adhesive materials for replantation of the root fragments on long-term dentin bond durability. Three dentin adhesive systems along with a composite core material and three MMA-based resin cements were used in this study. Root fragments sectioned from human incisors were bonded with one of the adhesive syste … More ms. The microtensile bond strengths were measured over one year immersed in water. It was found that the dentin bond durability was influenced by selection of the adhesive systems.Stress distribution within the enndodonticaly treated teeth with various kind of post and core and crowns were evaluated with three kinds of methods, that is, loading test with human extracted teeth, photoelastic analysis and finite element analysis. As a result, it has been clarified the combination of the post and core and the crown plays an important role in preventing the stress concentration within the root. Stress concentration can be prevented by using the crown fabricated with a high elastic modulus for the post and core with a high elastic modulus, and the crown fabricated with a low elastic modulus for the post and core with a low elastic modulus.Experimental fiber reinforced polymer-based root canal points improved resistance for vertical root fracture especially when the root apex was prepared larger. Crack lengths of artificially vertical-fractured teeth extended with time, but extension ratio of crack length was smaller when adhesive root canal sealer was used. New vertical fracture simulation system applying load from the root canal wall was designed, but the effect of root canal filling material using this new system was not significant. Fiber posts were expected to reduce vertical root canal fracture. Therefore, effects of fiber posts on polymerization of luting cement in root canal space were examined. Ability of polymerization was significantly different among the products used. Less