피로파절특성에 미치는 임플란트 지대주나사의 코팅영향

Abstract

Dental implant systems are subject to failure in the screw connection part which can occur due to screw loosening or fracture. For solving the problem of loosening, some researchers had carried out the TiN(titanium nitride) and WC(tungsten carbide) coating on the abutment screw, while fatigue failure may still be not researched as an issue of coating materials. In this study, fatigue test was performed to estimate the coating effects of abutment screw for implant system according to the ISO 14801. For this purpose, TiN and WC film coating was carried out on the abutment screw using EB-PVD and sputtering, respectively. In order to observe the coating surface of abutment screw, surfaces of specimens were observed by field emission scanning electron microscope(FE-SEM) and energy dispersive x-ray spectro- scopy(EDS). For the fatigue test, the implant fixture and abutment were tightened to a torque 32Ncm using digital torque gauge with a 0.1Ncm accuracy. The fatigue tests were carried out according to the ISO 14801. Each prepared samples were fixed to uniaxial sinusoidal cyclic loading machine(ADT-AV01k1, Shimadzu, Japan) under load control between 42-420N and 58-580N. Fractured surface was observed with FE-SEM. 1.The surface coated with TiN and WC showed the smooth surface at top, flank, valley of abutment screw. Whereas, the many scratches formed by the machine were observed on the surface of non-coated abutment screw. 2.The fatigue life of implant system used TiN(826,523 cycle) and WC(1,000,000 cycle) coated abutment screw was found to be relatively longer compared to 587,807 cycle of non-coated abutment screw at 420N. Whereas, fatigue life(41,451 cycle) of TiN coated sample showed longer than that of other samples. 3.From results of fatigue test at 420N, fatigue striations were showed on the fractured surface of non-coated abutment screw. The semi-cleavage surface was mainly observed on the TiN coated surface. Whereas, the fracture surface of semi-cleavage and ductile showed on the WC coated surface. 4.From results of fatigue test at 580N, the semi-cleavage surface was mainly observed on the TiN coated surface at crack initiation step, and fatigue striations were regularly appeared at crack propagation step with striation thickness of 0.5㎛/cycle. Whereas, In the case of WC coated abutment screw, slipbands and cracks moved into center of fracture surface with striation thickness of a few ㎛/cycle through three step of fracture; brittle crack pop-in and arrest, fatigue crack growth, and final ductile fracture. It is considered that the fracture behavior of abutment screw depended on coating materials on the abutment screw, and confirmed that TiN coating on the abutment screw can be improved the fatigue property by homogenizing the machined surface.