Influence of tungsten carbide/carbon coating of implant-abutment screw on screw loosening

Park, Jae Kyoung; Jeong, Chang Mo; Jeon, Young Chan; Yoon, Ji Hoon

Abstract

STATEMENT OF PROBLEM: Dental implant procedure has been recognized as a very effective treatment to rehabilitate fully or partially edentulous patients. However, mechanical failures such as screw loosening, screw fracture have been still reported frequently. PURPOSE: The purpose of this study was to evaluate the influence of tungsten carbide/carbon coating, which has superior hardness and frictional wear resistance, on implant-abutment screw loosening of three different joint connections after one million cyclic loading. MATERIAL AND METHODS: The values of detorque before and after loading were measured in three different joint connections (Osstem Implant, Korea), one external butt joint, US II implant system and two internal cones, SS II and GS II system. The values of detorque before loading was analyzed by one-way ANOVA, and two-way ANOVA and Scheffe'test were performed for the value of detorque after loading.
RESULTS
1. The values of initial detorque of tungsten carbide/carbon coated Ti alloy screw were smaller those of Ti alloy screw (P<.01), and there were no differences among implant systems in each screw (P>.05). 2. In comparison of loss rate of detorque value after cyclic loading, US II system was greater than SS II and GS II system but there was no difference between SS II and GS II system (P<.01). 3. Loss rates of detorque value after cyclic loading decreased consistently at tungsten carbide/carbon coated Ti alloy screw comparing with Ti alloy screw in all implant systems (P<.01), and there were no differences among three systems in reduction of loss rates by using tungsten carbide/carbon coated Ti alloy screw (P>.05).
CONCLUSION
Tungsten carbide/carbon coating to increase preload with reduction of friction resistance was a effective way to decrease screw loosening by functional loading.