The effect of simulated erosive conditions on the frictional behavior of different orthodontic bracket-wire combinations

Background.Frictional resistance is an important parameter in orthodontics that influences the effectiveness of archwire-guided tooth movement.Since the consumption of dietary acids has increased considerably over the last 2 decades, there is a rationale for investigating the process of degradation of orthodontic materials in an acidic environment and its effect on clinical efficiency.Objectives.The aim of this study was to evaluate the effect of simulated erosive conditions on the frictional behavior between the brackets of 3 different materials and 3 different wire alloys.Material and methods.Three types of twin orthodontic brackets (stainless steel (SS), monocrystalline ceramic and titanium) and 3 types of archwires of the same dimension (SS, nickel-titanium (Ni-Ti) and beta-titanium (titanium-molybdenum alloy -TMA) were tested in 9 different combinations under simulated erosive and non-erosive conditions (18 groups, n = 10).Bracket-wire specimens in the erosive-condition groups were subjected to a pH cycling regimen with 1% citric acid and artificial saliva for 5 consecutive days.Bracket-wire specimens from the non-erosive-condition groups were incubated only in artificial saliva for 5 days.Static and kinetic friction were determined by measuring the force needed to move the wire through the bracket.A three-way analysis of variance and pairwise comparisons with the Student-Newman-Keuls test were performed.Results.Irrespective of the conditions, SS brackets with SS wire demonstrated significantly lower mean static and kinetic frictional resistance than other bracket-wire combinations (p < 0.01).Ceramic and titanium brackets generated high frictional forces with all 3 types of wire tested.Erosive conditions did not significantly influence static and kinetic frictional resistance in all bracket-wire groups.Conclusions.Erosive conditions do not affect the frictional behavior of SS, Ni-Ti and TMA orthodontic archwires at a clinically significant level.