Distortion of three-unit implant frameworks during casting, soldering, and simulated porcelain firings.
OBJECTIVE
The aim of this study was to assess distortion inherent in casting, soldering, and simulated porcelain firings of screw-retained, implant-supported three-unit fixed partial dentures (FPDs).


METHODS
Ten wax patterns were fabricated on a die-stone cast containing two implants, 20 mm apart from center to center. Five specimens were cast in a high-palladium alloy, exposed to simulated porcelain firings, sectioned, and then soldered with low-fusing solder. Five specimens were cast, sectioned, soldered with high-fusing solder, and then exposed to simulated porcelain firings. For each specimen, two horizontal and six vertical distances between appropriately scribed reference points were measured with a traveling microscope. Comparisons were made among the various measurements taken after wax-pattern fabrication, casting, high- and low-fusing soldering, and each porcelain firing. Data were analyzed using a repeated-measures factorial ANOVA (alpha = 0.05).


RESULTS
Significant difference was detected in the amount of horizontal distortion during casting (53 +/- 24 microns) and high-fusing soldering (-49 +/- 50 microns), as well as in the amount of horizontal distortion during high-fusing soldering (-49 +/- 50 microns) and low-fusing soldering (17 +/- 26 microns). However, no clinically significant difference was found in the amount of horizontal distortion during casting, low-fusing, and high-fusing soldering. The greatest amount of distortion during the simulated porcelain firings took place during the oxidizing cycle.


CONCLUSIONS
Soldering did not improve the casting misfit of a three-unit implant-retained FPD model. Metal-ceramic implant frameworks should be oxidized before intraoral fit evaluation.
Zervas
P J
PJ
Ohio State University, College of Dentistry, Columbus 43210-1241, USA.
Papazoglou
E
E
Beck
F M
FM
Carr
A B
AB
D000704:Analysis of Variance; D000044:Dental Abutments; D003735:Dental Casting Technique; D003776:Dental Porcelain; D019094:Dental Prosthesis, Implant-Supported; D012994:Dental Soldering; D003779:Denture Design; D003830:Denture, Partial, Fixed; D006801:Humans; D016876:Metal Ceramic Alloys / Q000737:chemistry*
D016876:Metal Ceramic Alloys; D003776:Dental Porcelain