Celik Gozde, Uludag Bulent
University of Ankara, Faculty of Dentistry, Department of Prosthodontics, Ankara, Turkey.
J Prosthet Dent. 2007 Apr;97(4):229-35. doi: 10.1016/j.prosdent.2007.02.006.
There are various stress transfer studies of 2- or 4-implant-retained mandibular overdenture designs. However, the influence of various types of attachments and implant inclination on stress distribution of 3-implant-retained mandibular overdenture designs has not been sufficiently assessed.
The purpose of this study was to compare the load transfer characteristics of 4 attachment systems for 3-implant-retained mandibular overdenture designs for vertically oriented and inclined implants.
Two photoelastic mandibular models were fabricated having 3 screw-type implants (3.7 x 14 mm with 4.8-mm diameter abutment platform) embedded in the interforaminal region. In the first model, the implants were parallel to each other and vertically oriented. In the second model, 1 implant in the midline was vertically oriented, and the other 2 implants were positioned 20 degrees divergent from the center implant. Four retention mechanisms were studied for each model--the Locator, Swissplus ball, Bredent bar, and Bredent bar-ball. The bar design connected the 3 implants, and the bar-ball design used the bar in a similar fashion but additionally incorporated distally placed ball attachments. A vertical force of 135 N was applied unilaterally to the central fossa of the right first molar. The resultant stresses that developed in the supporting structure were monitored photoelastically and recorded photographically.
For the splinted and unsplinted 3-implant-retained overdenture designs evaluated, moderate and low level stresses were observed with different attachment systems. For both the vertically oriented and inclined implants, the bar-ball attachment system produced the lowest stress level.
For vertical and inclined implant designs, lowest stress was transferred to all implants with the bar-ball attachment system, while moderate stresses were observed in implants on the loaded side with unsplinted attachment systems. The highest stress level observed with all attachment systems was moderate. For the vertical implant design, the observed stresses were distributed to all implants except with the ball attachment system, which demonstrated little discernible stresses on the non-loaded side implant.
已有多项关于两颗或四颗种植体支持的下颌覆盖义齿设计的应力转移研究。然而，各类附着体及种植体倾斜度对三颗种植体支持的下颌覆盖义齿设计中应力分布的影响尚未得到充分评估。
本研究旨在比较用于垂直和倾斜种植体的三颗种植体支持的下颌覆盖义齿设计的四种附着系统的负荷传递特性。
制作了两个光弹性下颌模型，在孔间区域植入三颗螺钉型种植体（直径3.7×14 mm，基台平台直径4.8 mm）。在第一个模型中，种植体相互平行且垂直排列。在第二个模型中，中线处的一颗种植体垂直排列，另外两颗种植体与中间种植体呈20度发散排列。对每个模型研究了四种固位机制——Locator、Swissplus球、Bredent杆以及Bredent杆 - 球。杆式设计连接三颗种植体，杆 - 球式设计以类似方式使用杆，但额外在远端设置了球附着体。向右侧第一磨牙的中央窝单侧施加135 N的垂直力。通过光弹性监测并摄影记录支持结构中产生的合成应力。
对于所评估的联合支持和非联合支持的三颗种植体支持的覆盖义齿设计，不同附着系统观察到中等和低水平应力。对于垂直和倾斜种植体，杆 - 球附着系统产生的应力水平最低。
对于垂直和倾斜种植体设计，杆 - 球附着系统将最低应力传递至所有种植体，而在非联合支持附着系统的负荷侧种植体中观察到中等应力。所有附着系统观察到的最高应力水平为中等。对于垂直种植体设计，除球附着系统外，观察到的应力分布于所有种植体，球附着系统在非负荷侧种植体上几乎未显示出可察觉的应力。
