Precision of Fit of Titanium and Cast Implant Frameworks

Objectives: Among the aspects believed to affect the life-time survival of dental implants is the accuracy of the prosthesis framework. This study evaluated and compared the precision of fit of a CAD/CAM one-piece titanium fixed complete denture frameworks to that of conventional cast frameworks.

Methods: Ten Procera titanium substructures were fabricated using a CAD/CAM technique. Five cast implant frameworks of high noble metal (Palladium-Gold) were fabricated by 5 different dental laboratories. Laboratories were instructed to use their preferred technique to obtain the optimum fit. Using a Zeiss Coordinate Measuring Machine and CALYPSO measuring software, positions of implant replicas in the gypsum model were determined. Positions were then matched to the measured positions of the framework cylinders.

All samples were analyzed measuring the position of the replicas in the A translation matrix calculated by the rigid body transformation method. This method translates the cylinder positions and minimizes the point-to-point distance between the two data sets. The best fit between the replica and the framework was completed by making each corresponding cylinder the origin (0,0,0). This was done systematically until there were six best fit data sets from which the minimum gap data set was chosen. All the data were transformed into the coordinate system: Cylinder#1(0,0,0), #6(x,0,0), #3(x,y,0) prior to making comparisons.

Results: The following are the Centroid, MaxGap, MiniGap and the maximum minus minimum angular gap measurements between the implant replicas and the corresponding titanium and cast framework cylinders.

Method          Centroid        MaxGap         MiniGap         Maximum-Minimum

Cast                21.3                25.6                17.1                            8.5

Titanium          6.8                  7.6                  6.0                            1.7

Conclusions: CAD/CAM one-piece titanium fixed complete denture frameworks provide a more accurate precision of fit over that of cast frameworks.

<>Supported by NobelBiocare/ University of Michigan Center for Excellence