코팅된 지대주 나사의 반복 착탈 후 표면변화와 풀림력에 관한 연구

Abstract

At present, some implant makers are selling coated screws to prevent loosening of screws. But repeated closing and opening of screws induce abrasion of coated surface, so the effects may decrease. Recently researches about WC/C (Tungsten Carbide/Carbon) or TiN (Titanium Nitride) coating on screws are going on. It is reported that those coated screws improved abrasion, adaptability and detorque force. This study was to evaluate the effects of WC/C or TiN coated screws for solving the loosening phenomenon of screws which is a clinical problem. Surface changes and detorque values were compared with uncoated titanium screws (Group A) or WC/C coated screws (Group B) or TiN coated screws (Group C) after 10 times of repeated closing and opening test respectively. The results were follows; 1.Before repeated closing and opening of screws, somewhat rough screw surface with regular direction was observed in Group A. But coated granules with regular and smooth form were observed in Group B and Group C. 2.After repeated closing and opening of screws, abrasion and deformation of screw surface was observed in Group A and Group B. and exfoliation of coated granules was observed in Group B. But screw surface in Group C was little changed and relatively stable. 3.Weight loss of screws between before and after repeated closing and opening in Group A was bigger than that in Group B or Group C (P<0.05). 4.Detorque force in Group B or Group C was higher than that in Group A (P<0.05), and detorque force in Group C was higher than that in Group B but it was not a statistically significant level. 5.In all Groups, detorque force was increased in 3th or 4th repeated closing and opening of screws. After that, detorque force was decreased and Group A showed more prominent decrease tendency of detorque force than Group B and Group C. Conclusively, coated screws with WC/C or TiN did not show prominent surface changes than uncoated titanium screws even though they were repeatedly used. And they showed excellent resistance against friction and high detorque force. TiN coated screws showed better mechanical properties when it was compared with WC/C coated screws but it was not a statistically significant level. Thus it is considered that adaptation of WC/C or TiN coating on screws will decrease the screw loosening problem.