The purpose of this study was to examine the corrosion characteristics and the stability of each abutment screw according to coating materials. The 16 implant fixtures and the 16 titanium abutment screws of AVANA implant system(Soomin synthesis dental materials Co., Korea) were selected for this study, and the fixtures were 11.5 mm long and 3.75 mm diametric ones with external hexa-structure. Among the abutment screws, 4 screws were coated with Ti, 4 screws were coated with TiN, and 4 screws were coated with Ti/TiN by means of physical vapor deposition method. After that, the surfaces of abutment screws were observed, the unscrewing force of the screws were measured, the corrosion test of the screws was done and the crevice corrosion behaviors of the screws were observed through SEM.
The results were as follows :
1. Befor corrosion test, the unscrewing force of each abutment screw according to coating materials was 14.2 Ncm. That is to say, the unscrewing force of a titanium abutment screw, a Ti coated abutment screw and a TiN coated abutment screw was all the same. On the other hand, the unscrewing force of a Ti/TiN coated abutment screw was 13.6 Ncm.
2. After corrosion test, the unscrewing force of titanium abutment screw was 12.2 Ncm, that of a Ti coated abutment screw was 12.8 Ncm, that of a TiN coated abutment screw was 12.2 Ncm and that of a Ti/TiN coated abutment screw was 13.8 Ncm. thus the unscrewing force of a Ti/TiN coated abutment screw was the highest among them.
3. As the result of measuring the unscrewing force of the same abutment screw before and after corrosion test, a titanium abutment screw showed significantly lower unscrewing force after corrosion test than before corrosion test (p<0.05).
4. The corrosion potential of each abutment screw increased in the order of a titanium abutment screw, a Ti coated abutment screw, a TiN coated abutment screw and Ti/TiN coated abutment screw. On the other hand, re-passivation of each abutment screw was fast in the same order and the current density of each abutment screw decreased in the same order.
5. The gap between fixture and abutment screw and crevice corrosion decreased in the order of a titanium abutment screw, a Ti coated abutment screw, a TiN coated abutment screw, and a Ti/TiN coated abutment screw. On the other hand, the products of corrosion increased in the same order.
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