Mason M E, Triplett R G, Van Sickels J E, Parel S M
Department of Oral and Maxillofacial Surgery, University of Texas Health Science Center, San Antonio 78284.
J Oral Maxillofac Surg. 1990 Mar;48(3):311-7. doi: 10.1016/0278-2391(90)90401-m.
These case reports and review focus on three mandibular fractures that occurred through endosseous cylinder implant sites. The first patient, and most likely the second, had osteoporotic changes that affected their already atrophic mandibles. The third patient probably had an area of deficient mineralization or poorly consolidated bone in the region where the fracture developed. These bony conditions increased the potential for fracture. Although the exact mechanism by which such fractures occur is not known, an examination of past research suggests that stress concentration at the mandibular defect prepared for implant placement is a probable explanation. The site of an implant that has not yet osseointegrated acts as a site of tensile stress concentration and ultimately an area of weakness. Consequently, this area of weakness in a mandible with decreased bone density or mineralization is more prone to applied functional forces. Repeated submaximal functional forces in an area of bony weakness, such as an endosseous implant site, may lead to a spontaneous fracture with no associated trauma. With these factors in mind, several extra precautions should be taken when implants are placed in thin or weak mandibles.
这些病例报告及综述聚焦于发生在骨内柱状种植体植入部位的三例下颌骨骨折。首例患者，很可能第二例患者也一样，存在骨质疏松性改变，影响了其本就萎缩的下颌骨。第三例患者在骨折发生区域可能存在矿化不足或骨愈合不良的情况。这些骨质状况增加了骨折的可能性。尽管此类骨折发生的确切机制尚不清楚，但对以往研究的审视表明，为种植体植入准备的下颌骨缺损处的应力集中可能是一种解释。尚未实现骨整合的种植体部位会成为拉应力集中的部位，最终成为一个薄弱区域。因此，在骨密度或矿化程度降低的下颌骨中，这个薄弱区域更容易受到施加的功能力影响。在骨质薄弱区域，如骨内种植体部位，反复施加的次最大功能力可能导致无相关创伤的自发性骨折。考虑到这些因素，在将种植体植入薄或弱的下颌骨时应采取一些额外的预防措施。
