Detachment of Biofilm from Used Orthodontic Arch Wires

Objectives: Sliding mechanics is a treatment technique applied in orthodontic tooth movement. The prevailing notion is that resistance to sliding is mainly caused by friction. Friction is usually related to the type of material and norm load on the wire/bracket interface. This study investigated whether the intraoral accumulation of biofilm on orthodontic arch wires increases the resistance to tooth sliding.
Methods: Used and unused stainless steel (SS) and Nitinol (NiTi) rectangular orthodontic wires (0.016X0.022”, 0.017X0.025”) were divided into four groups of 15 used and 10 unused arch wires each. The used arch wires were intraorally maintained for at least one month. An Adhesion Accumulation Measuring Device (AAMD) was designed. The AAMD is composed of two perpendicular digital vernier calipers, which can be adjusted precisely to the desired rectangular-shaped aperture size. The AAMD was assembled on a universal testing machine. A straight piece of arch wire was attached to a load-cell and pulled (10 mm/min) through the AAMD. The force was acquired along 11mm.
Results: The force pattern of used arch wires of both types (SS, NiTi) was characterized by an inconsistent level of force with peaks when detachment of the biofilm occurred as compared to an almost constant plateau pattern of the unused arch wires. The mean force needed to pull the wires through the AAMD was 50% higher in the used vs unused arch wires (p<0.001). Peak force was 85% higher in the used vs unused arch wires (p<0.001). No difference in pulling force was found between alloys in unused arch wires. Arch wire size didn't affect the pulling force magnitude.
Conclusions: Biofilm build up on orthodontic arch wires is a key factor in resistance to orthodontic sliding technique. It should be removed from the arch wire prior to reactivation of tooth sliding mechanics.