Biomechanical analysis of fractures in the mandibular neck (collum mandibulae)

After treatment of fractures in the neck of the mandible by means of immobilization of the dentition, often more or less severe manifestations of malocclusion remain. It was hypothesized that this is caused by an altered articulation in the jaw joint on the affected side. Furthermore, it was hypothesized that an anteriorly displaced condyle, as observed frequently as a side effect of the treatment, is caused by pull of the lateral pterygoid muscle, despite maxillomandibular fixation.Intervention experiments were performed in silico to test these hypotheses. With a biomechanical model of the human masticatory system alterations were applied mimicking a fractured mandibular neck and configurations that had been observed after healing.It was predicted that the altered articulation in the jaw joint caused asymmetrical jaw movements despite symmetrical muscle activation. The jaw was predicted to close with an open bite similar to clinical observations. The predicted laterodeviations, however, were not in accordance with clinical observations. Despite maxillo-mandibular fixation the lateral pterygoid muscle was able to pull the mandibular condyle out of its fossa in anterior direction. Consequently, despite some methodological limitations, in general the predictions corroborated the hypotheses.     

不同剂量电离辐射对大肠癌细胞株HCT-8的多柔比星敏感性的研究

目的研究不同剂量电离辐射作用后多柔比星（阿霉素）对大肠癌多药耐药细胞株HCT-8细胞毒活性的影响,进一步探讨逆转大肠癌多药耐药性的方法.方法体外培养大肠癌细胞株HCT-8,以400 ng/ml阿霉素作为HCT-8细胞耐药模型刺激浓度制备细胞耐药模型.实验模型分为5组：假照射组;大剂量组（2 Gy）;0.05 Gy＋2 Gy组;0.1 Gy＋2 Gy组;0.2 Gy＋2 Gy组.采用MTT法测定给予阿霉素后大肠癌多药耐药细胞株HCT-8的存活率.结果与假照射组相比,2 Gy大剂量照射组及0.2 Gy＋2 Gy组照射后HCT-8细胞存活率明显降低（P＜0.05）,先给予低剂量照射（0.05 Gy,0.1 Gy）后,再给予大剂量照射,HCT-8细胞存活率降低更明显（P＜0.01）.与单纯2 Gy大剂量照射组比较,0.1 Gy＋2 Gy组HCT-8细胞存活率明显降低（P＜0.05）.结论先给予低剂量照射（0.1 Gy）后,再给予大剂量照射,可提高大肠癌多药耐药细胞株HCT-8对阿霉素的敏感性.