Surface Friction Behaviour of Anodized Commercially Pure Titanium Screw Assemblies

Dental implant abutment fixation by screw requires a prescribed preload (tensile screw load) for structural and implant performance purposes. This paper investigates the effect of surface modification on the apparent frictional behaviour of commercially pure Grade 4 titanium bolt assemblies by anodizing. 4 mm screws are anodized at various anodizing voltages to control the oxide layer thickness. Fixation torque is measured along with the corresponding tensile load in the screw and used to determine the dynamic surface friction coefficient for fastening and the static surface friction coefficient for untightening. Surface hardness is measured and linked to the frictional behaviour. The reduction in the apparent frictional behaviour are presented and discussed.