Friction Forces Generated by Esthetic TiNbTaZr (GUMMETAL) Orthodontic ArchWires

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Objectives: To evaluate the friction forces generated by TiNbTaZr (GUMMETAL) and rhodiumplated TiNbTaZr (esthetic GUMMETAL) archwires in comparison to conventional orthodontic archwires, analyzed according to bracket-wire angulation and archwire cleaning condition. Materials & Methods: A total of 192 samples of four different orthodontic archwires with dimensions of 0.019 x 0.025-inch were prepared. The archwires were stainless steel (SS), betatitanium (commercially known as titanium molybdenum alloy [TMA]), TiNbTaZr (commercially known as GUMMETAL), and rhodium-plated TiNbTaZr (commercially known as esthetic GUMMETAL). The samples were divided into two groups (N=96 per group): uncleaned and cleaned using 99% isopropanol. Then they were subdivided into three subgroups (N=8 per group) according to bracket-wire angulation: 0˚, 5˚, and 10˚. 0.022-inch slot SS maxillary right canine twin brackets with MBT prescriptions were used to test static and kinetic friction forces of the archwires according to bracket-wire angulation and cleaning condition. The wires were slid through the bracket slots vertically at a rate of 10mm/minute using a universal testing machine (Dillion Quantrol TC2i, Mecmesin) with a 100 N load cell and 150g weight to simulate clinical forces to retract a canine. Additionally, 0.5 % carboxymethyl cellulose artificial saliva drops with PH=7.0 were applied on every bracket-wire interface. Surfaces of representative specimens from each group were evaluated by scanning electron microscopy (SEM). Statistical analysis was performed using the Kruskal-Wallis test followed by pairwise comparisons of static and kinetic friction forces in uncleaned wires, cleaned wire, and between cleaned and uncleaned wires analyzed by wire-bracket angle using analysis of variance (ANOVA) with Tukey Honestly Significant Difference (HSD) adjustment for multiple comparisons with significance set at P<0.05. Results: Overall, there was a noticeable increase in static and kinetic friction forces among the archwire groups as the bracket-wire angle increased, irrespective of the cleaning condition. vi There were statistically significant differences in static and kinetic friction forces between archwires when analyzed by bracket-wire angulation and cleaning condition with the exception of the 0-degree uncleaned group where the differences between archwires were not statistically significant (P=0.010 for static friction and P=0.007 for kinetic friction). Friction forces were significantly different between cleaned and uncleaned wires within each bracket-wire angulation group. GUMMETAL wires had the lowest static and kinetic friction forces among all wires in the 0-, 5-, and 10-degree angulations. On the other hand, esthetic GUMMETAL wires showed significantly higher levels of friction at the 10-degrees angulation as compared to the 0- and 5- degrees. SEM analysis revealed that cleaning wires mildly altered the surface roughness of wire materials, with the exception of the esthetic GUMMETAL wire, it appeared that cleaning the wire with 99% isopropanol in an ultrasonic bath affected the rhodium plating and exposed the underlying surface. Conclusions & Clinical Implications: Overall, the static and kinetic friction forces of the GUMMETAL and esthetic GUMMETAL wires are comparable to SS. Esthetic GUMMETAL wires showed significantly higher friction forces than GUMMETAL, especially when the bracket-wire angulation was increased to 10-degrees and when they were cleaned with 99% isopropanol. Cleaning wires before their clinical use decreased observed surface roughness and the appearance of pits and fissures on the wires. The findings of this study suggest that GUMMETAL wires could be used for space closure with sliding mechanics, however, esthetic GUMMETAL wires are not ideal for the same purpose. Keywords: Fric