Konus crown 내관의 종류와 외관의 형성 방법에 따른 유지력 비교 연구

Abstract

The purpose of this study was to find the way to guarantee a long-term retention by evaluating the change of retentive force after repeated insertion/separation cycles and the retentive force acquired from single tooth according to the type of inner crown(Au-Ag-Pd Alloy, Zirconia) and the formatting method of outer crown(Casting, GES) of in vitro Konus crown. 4 groups of inner & outer crown were fabricated on the die formed by taking impression of the ideally prepared premolar resin tooth model with silicone rubber. 4 groups were as follows; Gold 1 group-gold inner crown and gold outer crown, Gold 2 group- gold inner crown GES outer crown, Zirconia 1 group- zirconia inner crown, gold outer crown, zirconia 2 group-zirconia inner crown, GES outer crown. In this study, all the other factors that affect retentive force except the type of inner crown and the formatting method of outer crown are unified with 6mm height , 2° of axial convergency, 1mm thickness of inner crown and 1mm width occlusal bevel of inner crown. Inner and outer crown were connected using static load compression tester with 5Kgf load. After 1, 100, 200, 300, 500, 1000, 3000, 5000, 7000, 10000 times of manual insertion/separation, retentive force was measured 5 times at each frequency using universal testing machine(Instron, Mssachusetts, USA).

The results were as follows:

1. Retentive force was increased in the order of Zirconia 2 group, Zirconia 1 group, Gold 2 group, Gold 1 group.

2. In all groups, reduction of retentive force was statistically significant according to the number of insertion/separation cycles (p<0.05).

3. In case of gold alloy inner crown, gold alloy outer crown was better than GES outer crown in retentive force. However, retentive force of gold alloy outer crown was decreased more than that of GES outer crown and became to be almost the same with that of GES outer crown after 10,000 times of insertion/ separation. In case of Zirconia inner crown, Gold alloy outer crown and GES outer crown had similar initial retentive force and decrement of retentive force, therefore they showed similar retentive force after 10,000 times of insertion/separation.

4. In case of gold inner crown, the amount of retentive force reduction decreased in a small portion with application of GES, but in case of zirconia inner crown, there was little difference with application of GES.