The Evaluation of Changes in Retention Force Values in Three-Element Telescopic Crown Systems using Simulated Load Cycles

The development of CAD/CAM technology created the possibility of using three-element telescopic crowns systems in various material combinations. Methods of verification of new solutions are necessary before their clinical use. The aim of the study was to develop a method of assessing the stability of the force retention in three-element telescopic crown systems in selected combinations of materials. Material and Methods: Material consisted of the three-element telescopic crown systems, collected in five groups: A (ZrOAuGalv-ZrO), B (ZrO-PMMA-ZrO), C (ZrO-AuGalv-CrCo), D (ZrO-PMMA-CrCo), E (ZrO-AuGalv-acrylic) and a control group (K: Au-AuGalv-CrCo). A fundamental part of the method was the special measuring device with software. The retention force was examined in the range of 0-30 000 cycles of engagement and disengagement of crowns. Results: There was no statistical significant differences between the changes of the retention force in groups A vs B and C vs D. The regression analysis showed that groups A and B are groups with the greatest stability. Conclusions: The telescopic crowns made from zirconia in CAD/CAM technology ensures the most stable retention force irrespective of the type of intermediate element. The special attention should be paid to the type of material from which the external crown will be made.