J Korean Acad Prosthodont.  2008 Oct;46(5):500-510. 10.4047/jkap.2008.46.5.500.

Detorque force and surface change of coated abutment screw after repeated closing and opening

• Jang JS
• Kim HJ
• Chung CH

• KMID: 2000407
• DOI: http://doi.org/10.4047/jkap.2008.46.5.500

Abstract

STATEMENT OF PROBLEM: Recently researches about WC/C (Tungsten Carbide/Carbon) or TiN (Titanium Nitride) coating on abutment screws are going on. It decreases friction coefficient, resistance against corrosion and withdrawal of physical fragility when the coating is applied to the metal surfaces. It is reported that coated abutment screws improved abrasion, adaptability and detorque force. PURPOSE: This study is about the effects of coated 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 uncoated titanium abutment screws (Group A) and coated abutment screws with WC/C (Group B) and TiN (Group C). Each group was made up of 10 abutment screws. RESULTS: 1. Before repeated closing and opening, Somewhat rough surface with regular direction was observed in Group A. Coated granules were observed in group B and group C and overall coated layer appeared in regular and smooth form. 2. Before repeated closing and opening, The coated surface showed bigger and thicker size of coated granules in Group C than Group B. 3. After repeated closing and opening, abrasion and deformation of abutment screw surface was observed in Group A and Group B. Exfoliation phenomenon was observed in Group B. 4. Group A showed biggest range of decrease when the weight changes of abutment screws were measured before and after repeated closing and opening. Group C showed less weight changes than Group B but there was no statistical difference between two groups. 5. Group B and Group C showed higher average detorque force than Group A and there was statistical difference. 6. Group A showed more prominent decrease tendency of average detorque force than Group B and Group C. CONCLUSION: Coated abutment screws with WC/C or TiN did not show prominent surface changes than uncoated titanium 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.

Keyword

Detorque force; Abutment screw; TiN; WC/C

MeSH Terms

Corrosion
Friction
Tin
Titanium
Tin
Titanium

Figure

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  Fig. 1. Kind of abutment screws used in this study. (Left: titanium screw, Middle: WC/C coated screw, Right: TiN coated screw)

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  Fig. 2. Torque wrench and digital device for the measurement of detorque force.

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  Fig. 3. SEM micrographs and EDX showing surface of each group. (Left: ×100, Middle: ×10,000, Right: EDX)

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  Fig. 5. Change of the abutment screw weight comparison between groups (∗: P < .05, One-way ANOVA; Turkey test).

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  Fig. 4. SEM micrographs and EDX showing surface of each groups. (Left: ×10,000, Middle: ×500,000, Right: EDX)

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  Fig. 6. Comparison with mean detorque forces.

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  Fig. 7. Comparison with mean detorque force between groups (∗: P < .05, One-way ANOVA; Turkey test).

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