Dimensional Changes of 3-Unit Implant-Supported Zirconia Frameworks of Two CAD/CAM Systems from Scanning to Sintering
Objectives: Internal fit of implant frameworks is an important factor determining the long-term success of dental implant restorations. This in vitro study aimed to evaluate dimensional changes of implant-supported zirconia frameworks fabricated by two computer-aided design/computer-aided manufacturing (CAD/CAM) systems from scanning to sintering.
Materials and Methods: A master model of a three-unit fixed partial denture was fabricated with two implant abutments. In each CAD/CAM system (AmannGirrbach and Zirkonzahn), the master model was scanned 12 times and data were saved as STL files (scanning groups). Using semi-sintered zirconia, 12 real-size frameworks (milling groups) and 12 enlarged frameworks which were then sintered (sintering groups) were made by each system. Dimensions of the master model and frameworks in each phase were measured. Dimensional changes (compared to the master model) were calculated. Data were analyzed using repeated measures ANOVA, independent t-test, and paired sample t-test at α = 0.05 of significance.
Results: Comparison of the two CAD/CAM systems revealed that although dimensional changes were greater in the Zirkonzahn system in the milling phase, they were greater in AmannGirrbach system in the sintering phase. Evaluation of fabrication phases in each system revealed greater dimensional changes in the milling phase compared to other phases in Zirkonzahn system (P<0.05). However, in AmannGirrbach system, the values were not significantly different between the milling and sintering phases (P>0.05).
Conclusion: Within the limitations of this study, the results showed that fabrication phases, type of CAD/CAM system and size of abutments had significant effects on dimensional changes.
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