外力直接撞击, 咀嚼咬到沙石、碎骨等硬物。be impacted by force,biting hard food. EtiologyClinic characteristics按部位分:冠折Crown fracture根折Root fracture冠根联合折Crown-root fracture按损伤和牙髓关系分:露髓不露髓冠折 crown fracture 前牙 : 横折、斜折Anterior tooth: horizontal or inclined后牙 : 斜折、纵折Posterior teeth:inclined or vertical根折 root fracture颈 1/3 、根中 1/3 、根尖 1/3cervix-thirds,middle-thirds,apical-thirds根折可有牙齿松动、叩痛、龈沟出血、粘膜触痛等。有的早期无明显症状，数日后出现。无根折外伤恒牙牙髓坏死率为 38 ％～59 ％根折牙牙髓坏死率为20 ％～24 ％，断端间隙利于炎症引流。X 片是诊断根折的重要依据Diagnosis can be carried out by radiographic examination冠根折 crown-root fracture以斜行多见，牙髓常暴露。The fracture will often be inclined with pulp exposure缺损少牙本质未暴露，磨光锐边。冠折 crown fractureWithout dentin exposure,selective grinding of the incisal edge is sufficient.牙本质暴露敏感者，盖髓树脂修复。Cover with Ca(OH)2 and composite resin restoration if dentin is expose and sensitive牙髓暴露，牙根发育完成者行活髓摘除术，牙根发育未完成者行活髓切断术。In case of a pulp exposure,pulpectomy is indicated if the root apical is developed,pulpotomy is sufficient if the root apical is developing. 根折 root fracture根中1/3 折，根尖1/3 折middle-thirds,apical-thirds用夹板固定三个月，如牙冠端有错位，在固定前应复位。Reposition the coronal fragment and use splinting for 3 months在治疗后1 、3 、6 、12 个月定期复查牙髓的活力状况，一旦发现牙髓有炎症或坏死趋势，则应作根管治疗术。Check for pulpal complications after 1 month,3 months,6 months and 12 months.If pulp necrosis occurs,root canal therapy should be done.颈1/3 折断：均先行根管治疗断端在龈上，根管治疗后桩核冠修复Cervix-thirds fracture:root canal therapy should be doneIf fracture surface above gingival level,a post-retained full crown is fabricated af...
