Mahidol University, Bangkok, Thailand.
J Prosthet Dent. 2011 Oct;106(4):266-71. doi: 10.1016/S0022-3913(11)60128-5.
Common complications of implant restorations are abutment screw loosening and screw fracture. The geometry of the implant-abutment connection may affect stresses generated from loading, and these stresses may have a role in screw loosening or fracture.
This study compared the load transfer characteristics of a complete-arch restoration supported by 4 implants with external and internal implant-abutment connections. Loads were applied to the prostheses in 3 positions.
Two-dimensional photoelastic models were used to simulate bone. Two types of implants (ReplaceSelect Internal-Interface Tapered Implants and ReplaceSelect External-Interface Tapered Implants) were placed in the photoelastic models. Complete-arch metal frameworks were fabricated on the abutments. Artificial teeth were arranged on the framework, and the prosthesis was screwed onto the abutments. The specimens were analyzed at 2 levels (implant-abutment level and apical to the implant level) with 3 loading conditions (4-point load; 2-point anterior load; and 2-point lateral load). The numbers of fringe orders were recorded and compared.
With the 4-point load, no stress differences occurred between the external-implant abutment connection and internal-implant abutment connection at the connection level and at the apical level. With the 2-point anterior load, the internal-implant abutment connection resulted in lower stresses at the connection level both in the loaded and non-loaded areas. With the 2-point lateral load, the internal-implant abutment connection resulted in lower stresses at the connection level at the non-loaded area.
When loaded off-center, the internal-implant abutment connection produced less stress when compared with the external-implant abutment connection.
种植体修复的常见并发症是基台螺丝松动和螺丝断裂。种植体-基台连接的几何形状可能会影响加载产生的应力，这些应力可能在螺丝松动或断裂中起作用。
本研究比较了 4 个种植体支持的全弓修复体的外部和内部种植体-基台连接的负载传递特性。将负载施加到修复体的 3 个位置。
使用二维光弹模型模拟骨。将两种类型的种植体（ReplaceSelect Internal-Interface Tapered Implants 和 ReplaceSelect External-Interface Tapered Implants）放置在光弹模型中。在基台上制作全弓金属框架。在框架上排列人工牙齿，然后将修复体拧到基台上。在 2 个水平（种植体-基台水平和种植体根尖水平）和 3 个加载条件（四点加载；两点前加载；和两点侧向加载）下分析标本。记录和比较条纹数。
四点加载时，连接水平和根尖水平的外部种植体-基台连接和内部种植体-基台连接之间没有产生应力差异。两点前加载时，内部种植体-基台连接在加载和未加载区域的连接水平上产生的应力较低。两点侧向加载时，内部种植体-基台连接在未加载区域的连接水平上产生的应力较低。
当加载偏心时，与外部种植体-基台连接相比，内部种植体-基台连接产生的应力较小。
