Effectiveness of screw surface coating on the stability of zirconia abutments after cyclic loading.
OBJECTIVE
Different surface treatments have been developed in attempts to prevent the loosening of abutment screws. The aim of the current study was to compare the effectiveness of titanium alloy screws with tungsten-doped diamond-like carbon (W-DLC) coating and uncoated screws in providing stability to zirconia (ZrO2) ceramic abutments after cyclic loading.


METHODS
Twenty prefabricated ZrO2 ceramic abutments on their respective external-hex implants were divided into two groups of equal size according to the type of screw used: uncoated titanium alloy screw (Ti) or titanium alloy screw with W-DLC coating (W-DLC/Ti). The removal torque value (preload) of the abutment screw was measured before and after loading. Cyclic loading between 11 and 211 N was applied at an angle of 30 degrees to the long axis of the implants at a frequency of 15 Hz. A target of 0.5 X 106 cycles was defined. Group means were calculated and compared using analysis of variance and the F test (α = .05).


RESULTS
Before cyclic loading, the preload for Ti screws was significantly higher than that for W-DLC/Ti screws (P = .021). After cyclic loading, there was no significant difference between them (P = .499).


CONCLUSIONS
Under the studied conditions, it can be concluded that, after cyclic loading, both abutment screws presented a significant reduction in the mean retained preload and similar effectiveness in maintaining preload.
Department of Dental Materials and Prosthodontics, Araraquara Dental School, UNESP - Universidade Estadual Paulista, São Paulo, Brazil. mariana_basilio@yahoo.com.br
Mariana de Almeida
Mde A
Basílio
Luis Eduardo
LE
Butignon
João  Neudenir
J
Arioli Filho
D001863:Bone Screws; D002516:Ceramics; D000044:Dental Abutments; D003799:Dental Stress Analysis; D016876:Metal Ceramic Alloys; D008855:Microscopy, Electron, Scanning; D014025:Titanium; D019415:Torque; D017973:Tungsten Compounds; D015040:Zirconium
D016876:Metal Ceramic Alloys; D017973:Tungsten Compounds; D015040:Zirconium; D014025:Titanium; C028541:zirconium oxide