Accuracy of implant-supported prostheses in the edentulous jaw: analysis of precision of fit between cast gold-alloy frameworks and master casts by means of a three-dimensional photogrammetric technique.

Distortions of 15 routine implant-supported prostheses were measured in relation to the master casts after completion by means of a 3-dimensional (3-D) photogrammetric technique. All prostheses were designed as one-piece gold-alloy castings with resin teeth. Five of the prostheses were placed in the edentulous maxilla, and the remaining were placed in the lower jaw. Distortion of the cylinders was mostly observed in the horizontal plane (x- and y-axis) while the vertical aspect seemed to be more stable. The mean 3-D center point distortion was 42 (SD 15) and 74 (SD 38) microns for the upper and lower jaws, respectively. The measurements revealed a range of 3-D center point distortion from 16 to 80 and 15 to 165 microns for the different jaws, respectively. The corresponding 3-D mean angular distortion of the cylinders was 51 (SD 35) microns in lower and 70 (SD 75) microns in the upper jaws. A correlation was found between 3-D center point distortion and the width as well as the curvature of the implant arch, indicating more displacement the wider and the more curved the arch was. The 3-D center point distortion was also significantly higher in the upper jaws which could possibly be explained by the curvature of the implant arch and higher numbers of implants in the upper jaws. Further problems with the fit of upper jaw castings could be related to more alloy in the castings and poor alignment of implants.