Basic and clinical research for root fracture

通过对X线片上根尖周射线可透性的新指标复杂度和径向SD进行评价，以鉴别根尖周炎和牙根纵裂。新的指标可能有助于牙根纵裂的诊断。如何分析牙科X线片的培训是非常重要的鉴别诊断牙根纵裂和根尖周炎。临床经验对正确诊断无显著影响，但医师专业差异有显著性。在牙科成孔显微镜下去除牙骨质后检测到不完全垂直骨折，并评价根管治疗后使用树脂涂层技术抑制冠渗漏的情况。观察桩核预备、树脂涂层、暂时化处理对染料渗透的影响，并评价咬合力与功能性牙位移的关系。上颌第一磨牙的牙体位移方向与咬合力方向基本一致，均为沿着腭尖方向。下颌第一磨牙咬合力的方向为根尖方向，牙齿位移路径为沿着舌向。评价牙槽骨水平对桩核修复后牙根抗折强度的影响。在正常骨模型下，铸造桩核的抗折强度最高。在骨吸收模型中，铸造桩核与纤维桩复合树脂的抗折强度无显著性差异，残牙结构对牙根折裂起重要作用，制备大锥度桩孔易引起牙根折裂。

New indexes, Complexity and Radial SD using periapical radiolucency were evaluated to make a differential diagnosis between apical periodontitis and vertical root fracture on a radiograph. New indexes could be useful for the diagnosis of vertical root fractures. Training on how to analyze dental radiographs is very important for the differential diagnosis between vertical root fracture and periapical inflammation. Whereas clinical experience had no significant effect on the correct diagnosis, the specialty of dentists showed a significant difference. An incomplete vertical fracture was detected after removing cementium under a dental poreating microscope.Coronal leakage inhabitation using a resin-coating technique after endodontic treatment was evaluated. The dye penetration was influenced by post space preparation, resin coating, and temporization.The relationship between occlusal force and tooth displacement in function was evaluated. The direction of the tooth displacement and that of the occlusal force of the upper first molar almost coinceded and they were along ahte palate-apical direction. In the lower first molar, the direction of occlusal force was in the apical direction, and the tooth displacement path was along the lingual direction. The influence of alveolar bone level on the fracture resistance of root restored with post and core was evaluated. With normal bone model, cast post and core showed the highest fracture resistance. In the resorbed bone model, there was no significant difference in fracture resistance between cast post and core and fiber post with composite resin.The remaining tooth structure played an important role in the root fracture and preparation of a post hole with a large taper easily caused root fracture.