Types of coating effects on the load deflection of three types of Stainless Steel archwires with fluoride application.

Nowadays, in the market, there are many coatings placed on the basic archwires to reduce the contact of Nickel-Titanium and stainless steel with saliva and oral tissue, improve aesthetics and decrease friction (Katić et al., 2015). Topical fluoride prophylactic agent significantly decreases the mechanical characteristics of the conventional archwire and may cause damage to the surface of the archwire, as a result, it would likely cause prolongation of orthodontic treatment (Shaza et al., 2012). The aim of this study was to evaluate and compare the effect of coating on load deflection with the use of acidulated phosphate fluoride agent for three types of stainless steel arch wires. Sixty cut pieces of 0.018 inches round arch wires were supplied from IOS Company, USA, twenty pieces were taken from each type of arch wires. These 60 cut pieces were arranged into 3 groups with 20 pieces for each group, half of each group were tested in dry conditions and the other half were tested in wet conditions following immersing in acidulated phosphate fluoride solution at 37˚C for sixty minutes. with the use of Instron universal testing machine, the Three-point bending test was done, each cut piece of arch wire loaded on the machine and tested at different deflections (0.5, 1.0, 1.5, 2.0) mm. with the use of computer-controlled software program (Tinius Horizon software), Load-deflection was recorded for each specimen. Then, the obtained data were analyzed using ANOVA and post hoc Tukey's test. A significant decrease was noticed in the loading forces of the conventional stainless steel arch wires following immersion in acidulated phosphate fluoride solution. On the other hand, acidulated phosphate fluoride did not show any effects on the load deflection and mechanical features of Rhodium coated arch wires. Gold-plated stainless steel archwires have been characterized of not being long-lasting and, as a result, have a tendency to rub off or deteriorate stainless steel core exposed. In conclusion, conventional stainless steel archwires deteriorated with acidulated phosphate fluoride; while gold layer was rub off from the gold-plated archwires, in contrast, Rhodium coating protected the archwire from the effect of acidulated phosphate fluoride and fluoride did not have significant effect on the loading force of these archwires.  Hence, the patient and the dentist should carefully use the fluoride containing products.