Mechanisms of vertical root fracture and clinical approach

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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