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KMID : 0362420080460050500
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Journal of Korean Academy of Prosthodontics
2008 Volume.46 No. 5 p.500 ~ p.510
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Detorque force and surface change of coated abutment screw after repeated closing and opening
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Jang Jong-Seok
Kim Hee-Jung
Chung Chae-Heon
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Abstract
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Statement of problem: Recently researches about WC/C (Tungsten Carbide/Carbon) or TiN (Titanium Nitride) coating on abutment screws are go-ing on. It decreases friction coefficient, resistance against corrosion and withdrawal of physical fragility when the coating is applied to the metal sur-faces. It is reported that coated abutment screws improved abrasion, adaptability and detorque force.
Purpose: This study is about the effects of coat-ed abutment screws on loosening of screw and for the purpose of solving the loosening phenomenon of abutment screws which is clinical problem.Material and methods:
Detorque force and surface changes are compared when 10 times of repeated closing and opening are applied to both un-coated titanium abutment screws (Group A) and coated abutment screws with WC/C (Group B) and TiN (Group C). Each group was made up of 10abutment screws.
Results: 1. Before repeated closing and opening, Somewhat rough surface with regular direction was observed in Group A. Coatedgranules were observed in group B and group C and overall coated layer appeared in regular and smooth form. 2. Before repeated closing and open-ing, The coated surface showed bigger and thicker size of coated granules in Group C than Group B. 3. After repeated closing and opening, abrasionand deformation of abutment screw surface was observed in Group A and Group B. Exfoliation phenomenon was observed in Group B. 4. Group Ashowed biggest range of decrease when the weight changes of abutment screws were measured before and after repeated closing and opening. GroupC showed less weight changes than Group B but there was no statistical difference between two groups. 5. Group B and Group C showed higher av-erage detorque force than Group A and there was statistical difference. 6. Group A showed more prominent decrease tendency of average detorqueforce than Group B and Group C.
Conclusion: Coated abutment screws with WC/C or TiN did not show prominent surface changes than uncoatedtitanium abutment screws even though they were repeatedly used. And they showed excellent resistance against friction and high detorque force.Thus it is considered that adaptation of WC/C or TiN coating on abutment screws will improve the screw loosening problem.
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KEYWORD
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Detorque force, Abutment screw, TiN, WC/C
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