COMPARISON OF SURFACE ROUGHNESS AND FRICTIONAL FORCES OF VARIOUS BRACKET AND ARCHWIRE COMBINATIONS – AN IN VITRO STUDY : Surface roughness and friction of bracket–archwire combinations

Abstract

Frictional resistance at the bracket–archwire interface opposes tooth movement during
sliding mechanics and is influenced by the surface roughness of the materials in contact.
This in vitro study compared the surface roughness and the static and kinetic frictional
forces of pre-adjusted edgewise Stainless Steel and Cobalt-Chromium brackets coupled
with Stainless Steel, Elgiloy and Titanium-Molybdenum Alloy archwires, before and
after subjecting them to friction. Ninety brackets and ninety archwires were tested in
six combinations of fifteen samples each. Friction was measured on a Universal Testing
Machine in the dry state. Surface topography of the bracket slots and the wires was
examined by Scanning Electron Microscopy and quantified with a non-contact optical
profilometer. Static friction exceeded kinetic friction in every combination. The Cobalt-
Chromium bracket with Stainless Steel archwire produced the least friction and the
Stainless Steel bracket with Titanium-Molybdenum Alloy archwire the most. Cobalt-
Chromium brackets were rougher than Stainless Steel brackets, and Titanium-
Molybdenum Alloy wires were roughest, both before and after friction; roughness
increased in every combination after sliding. Archwire material influenced frictional
behaviour more than bracket material, and the Cobalt-Chromium bracket with Stainless
Steel archwire appears the most favourable combination for sliding mechanics,
especially in nickel-sensitive patients.