所有选取的对象均无全身系统性疾病、无颌面部手术史及放、化疗史、无中、重度牙周炎及明显的口腔黏膜病。

None of these selected objects had the systemic disease, a history of maxillofacial surgery and radiotherapy and chemotherapy, moderate or severe periodontitis and significant oral mucosal disease.

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研究结果表明，在相同致伤条件下，伴有下颌骨骨折的颌面部火器伤的颅脑伤发生率高于无下颌骨骨折的颌面伤。

It was found that under the same wounding condition, the rate of cerebral damages was higher when the mandible was fracture than when the mandible was intact.

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结论：咬颌创伤，牙周疾病，牙髓无活力等是导致牙根纵裂的重要原因。

CONCLUSION: Traumatic occlusal force, periodontal lesions, teeth with root canal therapy are the major causes that led to vertical root fractures.

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