Friction resistance between edgewise brackets and archwires

This study quantified the dynamic frictional force encountered when TMA, Orthonol and multistranded stainless steel archwires were pulled a distance of 2mm through ceramic and stainless steel brackets. The current literature is inadequate and incomplete, for example, no data was found on rectangular multistranded archwires. The following factors were investigated: archwire material, archwire size, archwire-to-bracket angulation, bracket material, archwire and bracket slot surface roughness and lubrication in the form of artificial saliva. A total of 156 different combinations were investigated. A universal testing machine was used to pull the ligated archwires through the brackets, and record the friction. A four way analysis of variance with one nesting (archwire size) was carried out on 1,560 measurements to assess the results. All factors and interactions tested were significant in determining friction. Friction was found to increase with: archwire angulation and archwire size (exceptions were seen in some TMA archwires). Friction decreased with lubrication. There was a definite relationship between friction and archwire and bracket material. There was no definite relationship between archwire surface roughness and friction. Highest friction was observed with ceramic bracket and TMA archwire. The range of friction was 1.02 to 9.95 Newtons. The magnitude of the friction recorded is substantially larger than the forces applied in orthodontic movement clinically. It is proposed that the values recorded should be utilised as a means of comparing the effects of different factors, rather than for the quantification of friction in vivo.