In Vitro Comparison Of The Different Retention Adjustment Of Telescopic Crowns

Objective The research conducts experiment in vitro mainly through the slit telescopic crown technology, the gold-plating technology in the internal surface of the outer crowns and the conventional precious metal and the none-precious metal telescopic crown, approaching and consummating the retention readjustment and the remedial measure of the non-precious metal dual overlap system, extending the service life.Methods A total of 27 cylinder dies is in standard size of diameter 6mm, height 10mm.18 dies of them casted with Co-Cr alloy, 9 dies casted with Au-Pd alloy, standard metal dies were prepared by lathe, random divided into three groups: conventional Co-Cr alloy group, Co-Cr alloy slit telescopic crown group, Au-Pd alloy group, 9 dies every group, 4.5mm cervical diameter, 5mm height, 4o axial convergence. Co-Cr alloy slit telescopic crown group had 0.25mm depth concave on shoulder. Three groups substituted the preparation bodies of the base teeth and the inner crowns , the outer crowns made with the same material alloy. The slit telescopic crown group made a slit on the corresponding to the concave. The thickness of the outer crowns was 0.5mm. The metal dies and the outer crowns distinctly were fixed with autopolymerizing acrtlic resin. To measured all of dies using the electronic universal testing machine, and record the pulling force. After repeated insertion/separation cycles, the retention of The conventional Co-Cr alloy crown was dropped, plating gold in the internal surface of the outer crowns, then to measure the pulling force again.Results The retention of Au-Pd crown group and Co-Cr alloy slit telescopic crown was larger than that of conventional Co-Cr alloy crown group and gold-plating group, there were statistical significant(p<0.05).The max retention of Co-Cr alloy slit telescopic crown group was larger than gold-plating group, there were statistical significant(p<0.05). Between the group of conventional Co-Cr alloy crown and gold-plating crown, there were not any statistical significantthe (p>0.05). Between Au-Pd crown group and Co-Cr alloy slit telescopic crown group, the retention of 800 procedures was not any statistical significant (p>0.05). The retention of other all procedures was statistical significant (p<0.05).Conclusions The Co-Cr alloy slit telescopic crown technology enable the effect which the telescopic crown the retention drops with the precious metal to be similar; After repeated insertion/separation cycles, the retention of The conventional Co-Cr alloy crown was dropped, the gold-plating technology made the retention to increase, and the effect of dropping was similar with conventional Co-Cr alloy crown group.