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
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