SS Archwire Research Articles

Breakdown potential and repassivation ability of Ni–Ti and SS archwires

Breakdown potential and repassivation ability of Ni–Ti and SS archwires

A comparative study of frictional resistance during simulated canine retraction on typodont model.

Objectives:Frictional resistance is an important counterforce to orthodontic tooth movement during sliding mechanics. This study was carried out to evaluate the effect of different bracket-archwire-ligation combinations on “resistance to sliding” during simulated canine retraction on typodont model.Materials and Methods:the frictional resistance was tested between three modern orthodontic brackets-stainless steel, ceramic, and ceramic with metal slot (0.022-inch), and seven different archwires (0.019 × 0.025-inch)-stainless steel, nickel-titanium, Teflon coated stainless steel, stainless steel with the reverse curve of spee (RCS), Teflon coated stainless steel with RCS, Teflon coated nickel-titanium and nickel-titanium with RCS ligated with stainless steel ligature wire and regular clear elastomeric modules. All tests were carried out in a dry state on an Instron universal testing machine (crosshead speed: 0.5 mm/min). 10 measurements were made from each bracket-archwire-ligature combinations.Results:The highest mean frictional resistance was found in ceramic brackets with nickel-titanium RCS archwire ligated with elastomeric modules while minimum frictional resistance was found in stainless steel brackets with Teflon coated stainless steel archwire ligated with stainless steel ligature. Metal slot ceramic brackets generated significantly lower frictional forces than ceramic brackets, but higher values than stainless steel brackets. Teflon coated archwires shows highly significant reduction of the frictional resistance than their corresponding uncoated archwires. Archwires with RCS had the higher frictional resistance than normal counterpart archwires.Conclusion:Ceramic brackets with metal slot and Teflon coated SS archwires seem to be a good alternative to conventional stainless steel brackets and archwires in space closure with sliding mechanics in patients with esthetic demands.

Frictional forces between lingual brackets and archwires measured by a friction tester.

Frictional resistance tends to rapidly increase as the angle between a bracket and an archwire increases beyond a critical angle. The purpose of this study was to determine a new measuring method with a pin on disk friction tester for the measurement of the frictional force between lingual brackets and archwires. A lingual bracket is different from a labial bracket in dimensions and in some clinical aspects. The influence of artificial saliva was also surveyed. Two brands of lingual brackets and one brand of labial standard bracket with an 0.018-inch slot size were used. Archwires of three alloys (stainless steel [SS], Ormco; beta-Titanium [TM], Ormco; cobalt-chrome, [EL], RMO) with 0.016 x 0.022- and 0.017 x 0.025-inch dimensions were used. Measurements were conducted with an angular velocity of 0.6 degrees/s for 90 seconds and a normal force of 100 g at 25 degrees C in a dry and 34 degrees C in an artificial saliva environment. For SS and EL archwires, the frictional force with the FJT bracket was greater than that with ORM bracket (P < .01). Compared with SS and TM archwires, 0.016 x 0.022-inch EL archwire showed a higher frictional force with two lingual brackets (P < .01). Significant differences in frictional force existed between dry and artificial saliva environments (P < .05), and the effects varied by the bracket-archwire couples. The estimated critical contact angles were greater than the theoretical values. This new method can be a useful protocol for measurement of frictional force because it can measure the frictional force under the conditions of continuous angular change between bracket and archwire.

Effect of salivary viscosity on frictional coefficients of orthodontic archwire/bracket couples

Stimulated whole saliva samples were collected from 30 healthy individuals and analysed with a cone and plate viscometer. On the basis of these dynamic viscosity measurements saliva from patients, who represented the mean value and two standard deviations above and below the mean value, were selected for frictional force testing. Four archwire/bracket couples (SS/SS, SS/PCA, ~-Ti/SS, and I3-Ti/PCA) were each tested in these three salivas as well as in the dry state a total of five times, each at five different normal loads. With two exceptions no significant differences were found between any of the three wet states for any couple studied. When the dry state was compared to any of the wet states, the SS archwire couples showed a singificant increase in frictional forces, while the 13-Ti archwire couples showed a slight decrease in frictional forces, which was not statistically significant.