IADR Abstract Archives
In-vitro Study on the Behaviour of Retention Forces of Double-crown Systems Over the Time
Objectives:
The aim of this in-vitro study was to compare the development of the retention forces of different double crown systems after 10.000 insertion and separation cycles.
Methods:
Five different groups of double crowns were tested (n=10/group ):
1. Primary crown: Zirconium-dioxide (0°) / electroplated formed matrice
2. Primary crown: Zirconium-dioxide (2° cone angle) / electroplated formed matrice
3. Primary crown: Au-Pt- alloy / Matrice: Au-Pt-alloy
4. Primary crown: Cast chromium-cobalt alloy / Matrice: Cast chromium-cobalt alloy
5. Marburg double crown system
To prove standardized identical dimensions not only the zirconium-dioxide primary crowns but also the resin patterns for the cast primary crowns were fabricated by a CAD/CAM system. Each of the 50 double crowns was subjected to 10.000 insertion / separation cycles in a universal testing machine. For each specimen about 450 measurements of the retention force were recorded. To minimize the influence of tensile stress during the testing program, the primary and secondary crowns were mounted in a custom-made device which ensured axial loading.
Results:
The double crowns consisting of zirkonium-dioxide and electroplated galvanogold showed constant retentive forces during all insertion / separation cycles. The final retention force in group 3 (Au-Pt- alloy / Au-Pt-alloy) was about 10 % lower than the initial measurement. The non-precious cobalt-chromium-alloy showed a decrease of about 40 % after 10.000 cycles. The measurements of the Marburg double crown system decreased 40 to 50 %. Different traces of wear could be investigated by a light and a scanning electron microscope.
Conclusions:
All double crown systems showed a clinical sufficient wear behaviour. Concerning long time wear differences between the tested materials could be observed. It seemed to be that the combination of Zirconia/electroplated gold is most promising to achieve even retention forces over the time.
The aim of this in-vitro study was to compare the development of the retention forces of different double crown systems after 10.000 insertion and separation cycles.
Methods:
Five different groups of double crowns were tested (n=10/group ):
1. Primary crown: Zirconium-dioxide (0°) / electroplated formed matrice
2. Primary crown: Zirconium-dioxide (2° cone angle) / electroplated formed matrice
3. Primary crown: Au-Pt- alloy / Matrice: Au-Pt-alloy
4. Primary crown: Cast chromium-cobalt alloy / Matrice: Cast chromium-cobalt alloy
5. Marburg double crown system
To prove standardized identical dimensions not only the zirconium-dioxide primary crowns but also the resin patterns for the cast primary crowns were fabricated by a CAD/CAM system. Each of the 50 double crowns was subjected to 10.000 insertion / separation cycles in a universal testing machine. For each specimen about 450 measurements of the retention force were recorded. To minimize the influence of tensile stress during the testing program, the primary and secondary crowns were mounted in a custom-made device which ensured axial loading.
Results:
The double crowns consisting of zirkonium-dioxide and electroplated galvanogold showed constant retentive forces during all insertion / separation cycles. The final retention force in group 3 (Au-Pt- alloy / Au-Pt-alloy) was about 10 % lower than the initial measurement. The non-precious cobalt-chromium-alloy showed a decrease of about 40 % after 10.000 cycles. The measurements of the Marburg double crown system decreased 40 to 50 %. Different traces of wear could be investigated by a light and a scanning electron microscope.
Conclusions:
All double crown systems showed a clinical sufficient wear behaviour. Concerning long time wear differences between the tested materials could be observed. It seemed to be that the combination of Zirconia/electroplated gold is most promising to achieve even retention forces over the time.
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