Department of Removable Prosthodontics and Gerodontology, Tokyo Dental College, 1-2-2 Masago, Mihama-ku, Chiba city, Chiba, 261-8502, Japan.
J Prosthodont Res. 2010 Oct;54(4):179-84. doi: 10.1016/j.jpor.2010.04.004. Epub 2010 May 10.
The All-on-4 is used in the therapy of edentulous mandibles. However, few studies have investigated the effect of such implants on supporting bone. To clarify differences in stress in peri-implant cortical bone between 2-patterns of 6 implants and 8-patterns of 4 implants with change in inclination angle based on the All-on-4.
Three-dimensional finite element analysis models based on the mean value of the Japanese edentulous mandible were constructed. Implants 13 or 15 mm in length were inserted between the mental foramina. In the 6-implant model, implants were inserted in parallel. In the 4-implant model, the 2 anterior implants were inserted in parallel and the 2 posterior implants in parallel or on a slant. Implants were splinted with a superstructure. A 50 N load was applied to the occlusal surface under condition A, at 2mm distal from the distal implant, or condition B, at the distal end of the superstructure. Maximum von Mises stress on cortical bone was measured.
Stress was concentrated around the posterior-most implant on the right side. Under condition A, stress increased with 4 implants and increase in angulation. At 45°, stress increased by 23% of that in the 6-implant model. Under condition B, stress increased with 4 implants, although stress decreased with increase in angulation. At 45°, stress decreased by 45% of that in the 6 implants.
The use of 4 implants or inclined implants increased stress on peri-implant cortical bone. However, when used in conjunction with a short cantilever, inclined implants decreased stress on peri-implant cortical bone.
All-on-4 被用于无牙颌下颌骨的治疗。然而，很少有研究调查这些种植体对支持骨的影响。为了阐明基于 All-on-4 的两种 6 种植体模式和 8 种植体模式（种植体倾斜角度不同）在种植体周围皮质骨中的应力差异。
基于日本无牙颌下颌骨的平均值构建了三维有限元分析模型。长度为 13 或 15mm 的种植体插入颏孔之间。在 6 种植体模型中，种植体平行插入。在 4 种植体模型中，前 2 个种植体平行插入，后 2 个种植体平行或倾斜插入。种植体用上部结构连接。在条件 A（距远侧种植体 2mm 处的牙合面施加 50N 负载）或条件 B（在上部结构末端施加 50N 负载）下，测量皮质骨上的最大 von Mises 应力。
应力集中在右侧最靠后的种植体周围。在条件 A 下，随着 4 个种植体和角度增加，应力增加。在 45°时，应力增加了 6 种植体模型的 23%。在条件 B 下，随着 4 个种植体的使用，尽管角度增加导致应力减小，但应力仍增加。在 45°时，应力减少了 6 种植体的 45%。
使用 4 个种植体或倾斜种植体增加了种植体周围皮质骨的应力。然而，当与短悬臂结合使用时，倾斜种植体减少了种植体周围皮质骨的应力。
