Influence of Diverse Surface Finishes on the Frictional Resistance of Nitinol Wire

Nitinol wire is commonly used in Orthodontic appliances due to its large strain recovery, which enables efficient tooth movement. The objective of this study is to determine the influence of five commercially available surface finishes on the frictional resistance and surface roughness of Nitinol rectangular wire in a common orthodontic size. Various samples were shape set to simulate archwire heat treatment, and etched to remove surface oxides. Frictional testing was performed in a cross cylinder mode with a vertical load of 300 mN applied and the bottom specimen was moved over 3 mm with a 1 mm/s velocity in a reciprocating mode for 4 cycles. Friction force (Fx) and normal force (Fz) were recorded during the test. Coefficient of friction (COF) was obtained from the ratio of Fx to Fz. Surface roughness testing was performed by a non-contact, longitudinal vision method and 3D-RMS values were recorded. This study will detail the methods utilized in analyzing the results and the potential impact on surface finish selection for Orthodontic applications.