Roughness of Orthodontic Archwires: An MEV and AFM Study

Objectives: Evaluate the topographic surface of orthodontic archwires through Scanning Electron Microscopy (SEM) and Atomic Force Microscopy (ATM) to provide useful information to support clinical decisions.
Methods: For this purpose three alloys used to manufacture archwires (.019 "x .025") were used: stainless steel (SS), nickel-titanium (NiTi) and beta-titanium (TMA), manufactured by Dental Morelli, Brazil (MOR); Ormco, USA (Ormco); Smart Beijing Technology, China (BST); TP Orthodontics, USA (TP) and G&H Orthodontics, USA (GH). Segments collected from each sample units were grouped into 12 groups according to the alloy and the manufacturer: G1 SS (MOR); G2 SS (ORMCO); G3 SS (GH); G4 SS (TP); G5 NiTi (MOR); G6 NiTi (ORMCO); G7 NiTi (BST); G8 NiTi (TP); G9 TMA (MOR), G10 TMA (ORMCO); G11 TMA (BST) and G12 TMA (TP). In the beta-titanium wires groups one of them with coatings by ion implantation (G12) were used for comparison purposes and the others three was uncoated archwires (G9, G10 and G11). All 120 segments were evaluated as received from the manufacturer by SEM analyses (SSX-550, Shimadzu, Japan) and two digital images (100x, 1000x) of each sample obtained of randomly chosen regions. Tree samples in each group underwent performed AFM analysis (SPM-9500J3 SHIMADZU) operating in contact mode with silicon nitride probes (NANOSENSORS), scanner were performed with vertical variation of 8 μm and 20x20 μm area reading average roughness (Ra/μm) and processed by J Image software.
Results: Variance Analysis according to two-way (factors "brands" and "alloy") and Tukey complementary comparison method between groups (α = 5%) were used. Only the type of alloy was significant factor (p = 0.002). Data for different group alloy type independent of brands demonstrated that TMA (30.73 ± 11.93, mean ± SD, respectively) showed significantly higher values of Ra (p <0.05) than NiTi (16.50 ± 11.96) and SS (15.19 ± 5.93) alloys. It should be noted that there was no statistically significant difference Ra between standard TMA and TMA ion-implanted wires.
Conclusions: It was concluded that orthodontic archwires manufactured with beta titanium alloy have higher roughness, which suggests that its use may involve the effectiveness of tooth movement, corrosion behavior and aesthetics.