Microscopic study of surface roughness of four orthodontic arch wires

Aim/purpose Comparative evaluation of surface roughness of stainless steel (SS), nitinol (NiTi), titanium molybdenum alloy (TMA) and copper nitinol (Cu NiTi) orthodontic arch wires before and after clinical use to find the smoothest wire surface best used in orthodontic sliding mechanics. Materials and methods Surface roughness of 40 arch wires divided into four groups (group 1: 10 SS arch wires, group 2: 10 NiTi arch wires, group 3: 10 TMA arch wires and group 4: 10 Cu NiTi arch wires) were measured at five different points for each wire before and after its clinical use in oral cavity for 4 weeks using atomic force microscope and optical digital microscope. All obtained data was statistically tested. Results SS arch wires had the smoothest surface (average roughness: 17.38 μm for new wires and 104.1 μm for used wires) and Cu NiTi arch wires had the roughest surface (average roughness: 221.12 μm for new wires and 499 μm for used wires) with high significant differences between both groups either new or used arch wires (P 0.001). High significant difference was found between new and used wires for all groups. NiTi wires had greater surface roughness (average roughness: 211.8 μm for new wires and 313.8 for used wires) than TMA wires (average roughness: 138.5 μm for new wires and 221.2 μm for used wires). Conclusion SS orthodontic arch wires exhibited the least amount of surface roughness and advocated to be used in sliding mechanics to minimize the friction during orthodontic tooth movements.