Frictional Forces of Conventional and Improved Superelastic NiTi-Alloy Orthodontic Archwires in Stainless Steel and Plastic Brackets

Abstract

AbstractThis study evaluated the static and kinetic frictional forces produced between different combination of orthodontic archwires and brackets. Three types of archwires were examined: (1) stainless steel, (2) conventional NiTi alloy, and (3) improved superelastic NiTi alloy. Two types of brackets were tested: (1) stainless steel and (2) plastic. Both static and kinetic frictional forces were measured on a customdesigned apparatus under elastic ligature in the dry state. Each archwire-bracket combination was subjected to 20 independent evaluations. All data were statistically analyzed using two-way analysis of variance and Duncan’s test. The experimental results indicated that the static frictional force was significantly higher than the kinetic frictional force in all archwire-bracket combinations. The frictional force was lower for the stainless steel bracket than for the plastic bracket with stainless steel wire and the improved superelastic NiTi-alloy wire. The frictional force was lower for the improved superelastic NiTi-alloy wire than for NiTi wire with the stainless steel bracket, but higher for NiTi wire with the plastic bracket. The frictional force was lowest for stainless steel wire for both two types of bracket. This study demonstrates that the frictional forces of brackets are influenced by different combinations of bracket and archwire, and that the improved superelastic NiTi-alloy wire does not exhibit “low friction” (as claimed by the manufacturers) in all cases.KeywordsFrictional forceNiTi-alloy wireimproved superelastic NiTi-alloy wirestainless steel bracketplastic bracket