Tan K B, Rubenstein J E, Nicholls J I, Yuodelis R A
Department of Restorative Dentistry, National University of Singapore.
Int J Prosthodont. 1993 Jul-Aug;6(4):346-63.
The three-dimensional distortions of implant frameworks of two designs, reflecting the early "Toronto" U-shaped design and a current L-shaped design, were measured. A conventional commercial laboratory one-piece casting method, using a silver-palladium alloy, was used. Distortion was defined by five displacement variables for the centroids of each of five gold cylinders incorporated in each casting: three orthogonal translational displacements (dx, dy, and dz) and two rotational displacements (d theta x and d theta y). A computerized coordinate measuring machine was used. Overall translational displacements measured were -17.4 +/- 15 microns for dx, 6.1 +/- 7.1 microns for dy, and -0.1 +/- 1.7 microns for dz. The overall global translational displacement, dR, was 20.2 +/- 14.5 microns. Overall rotational displacements were -0.098 +/- 0.109 degrees for d theta x and -0.020 +/- 0.097 degrees for d theta y, giving an average absolute angular change, d theta R, of 0.158 +/- 0.077 degrees. No significant differences were found between U- and L-shaped castings, except for dy values for cylinders 2, 3, and 4, and d theta x values for cylinder 1. Cylinder location within the arch was associated with a specific direction and magnitude of translational and rotational displacement. Even small rotational displacements may manifest large gap appearances with the one-screw test because of the "moment arm" effect. However, other rotational displacements may be hidden, depending on the direction of tilt and the moment arm length.
测量了两种设计的种植体框架的三维变形情况，这两种设计分别反映了早期的“多伦多”U形设计和当前的L形设计。采用了传统的商业实验室一体式铸造方法，使用银钯合金。变形由每个铸件中包含的五个金圆柱体的质心的五个位移变量定义：三个正交平移位移（dx、dy和dz）和两个旋转位移（dθx和dθy）。使用了计算机化坐标测量机。测量得到的总体平移位移，dx为-17.4±15微米，dy为6.1±7.1微米，dz为-0.1±1.7微米。总体全局平移位移dR为20.2±14.5微米。总体旋转位移，dθx为-0.098±0.109度，dθy为-0.020±0.097度，平均绝对角变化dθR为0.158±0.077度。除了圆柱体2、3和4的dy值以及圆柱体1的dθx值外，U形和L形铸件之间未发现显著差异。牙弓内圆柱体的位置与平移和旋转位移的特定方向和大小相关。由于“力臂”效应，即使是小的旋转位移在单螺钉测试中也可能表现出较大的间隙外观。然而，其他旋转位移可能会被隐藏，这取决于倾斜方向和力臂长度。
