Dashti Mohammad Hossein, Atashrazm Parsa, Emadi Mehdi Imani, Mishaeel Shiva, Banava Sepideh
Department Prosthodontics, Boston University School of Dental Medicine, Boston, MA 02118, USA.
Quintessence Int. 2013;44(8):585-90. doi: 10.3290/j.qi.a29753.
Two commonly used attachment systems for implant-retained overdentures are bar and ball systems. The aim of this study was to compare these two types of attachments on the basis of the stresses introduced to the mandibular posterior residual ridge by an overdenture retained by two implants.
A basic model was generated from the data provided by a CT scan of a patient's mandible, the diagnostic casts, and the existing overdenture. Two root-form implants were placed in the anterior mandible. Models were used to simulate two situations: The first model represented an edentulous mandible supporting an overdenture retained by two implants connected with a bar and plastic clip system, and in the second model two ball attachments with nylon caps were used as the retention mechanism. A 35 N vertical load was introduced to the first molar region of each group to simulate the occlusal forces of the maxillary complete denture. The stresses in the mandibular residual ridges under the first molar region were measured using Ansys software.
The bar-retained overdenture introduced higher stresses to the posterior mandibular residual ridge compared to the ball-retained overdenture (0.4 MPa and 0.1 MPa, respectively).
Within the limitations of this study, the ball system was shown to introduce a lower amount of stress to the posterior mandibular residual ridge compared to a bar and clip system.
用于种植体支持覆盖义齿的两种常用附着系统是杆式和球帽式系统。本研究的目的是比较这两种附着类型在由两颗种植体支持的覆盖义齿对下颌后牙区剩余牙槽嵴所产生应力方面的情况。
根据患者下颌骨的CT扫描数据、诊断模型以及现有的覆盖义齿生成一个基础模型。在下颌前部植入两颗根形种植体。模型用于模拟两种情况：第一个模型代表无牙下颌支持由杆和塑料夹系统连接的两颗种植体所支持的覆盖义齿，第二个模型使用带有尼龙帽的两个球帽附着体作为固位机制。在每组的第一磨牙区域施加35N的垂直载荷以模拟上颌全口义齿的咬合力。使用Ansys软件测量第一磨牙区域下方下颌剩余牙槽嵴的应力。
与球帽固位的覆盖义齿相比，杆固位的覆盖义齿对下颌后牙区剩余牙槽嵴产生的应力更高（分别为0.4MPa和0.1MPa）。
在本研究的局限性内，与杆和夹系统相比，球帽系统对下颌后牙区剩余牙槽嵴产生的应力较低。
