Friction forces generated by aesthetic Gummetal(R) (Ti-Nb) orthodontic archwires: A comparative in vitro study.

OBJECTIVE: The aim of this in vitro study was to compare friction forces generated by the following archwires: rhodium-plated aesthetic Gummetal(R) (E-GM), Gummetal(R) (GM), stainless steel (SS) and titanium-molybdenum alloy (TMA), according to bracket-wire angulation and archwire cleanliness. METHODS: One hundred and ninety-two samples of four orthodontic alloys (E-GM, GM, SS, and TMA) were prepared. The samples were divided into two groups: uncleaned and cleaned using 99% isopropanol in an ultrasonic bath, then subdivided into three subgroups according to bracket-wire angulation: 0 degrees , 5 degrees and 10 degrees . Using a universal testing machine, the wires were pulled through SS maxillary right canine brackets to test static friction forces according to bracket-wire angulation and wire cleanliness. Representative specimens were evaluated to assess surface morphology and roughness. RESULTS: There were significant differences in static friction forces between archwires when analysed by bracket-wire angulation and cleanliness (P<0.001) except for the 0 degrees uncleaned group. Overall, TMA archwires produced the highest friction while SS wires showed the lowest friction at 0 degrees and 5 degrees . E-GM wires showed comparable friction to SS at 0(o) (cleaned and uncleaned), but significantly higher friction than SS at 5(o) (uncleaned) and 10 degrees (cleaned). GM wires had comparable friction to SS at 0 degrees (cleaned and uncleaned), but significantly less friction at the 5 degrees (cleaned) and 10 degrees (cleaned and uncleaned). Compared to GM, E-GM had significantly higher friction at 5(o) and 10 degrees (cleaned and uncleaned). Cleaning wires reduced surface roughness but increased overall friction. CONCLUSION: E-GM wires generate higher frictional resistance forces compared to GM and SS, especially at higher bracket-wire angulations and when cleaned. GM friction forces are comparable to SS and thus could be used for space closure with sliding mechanics. However, E-GM wires are not ideal for the same purpose.