A comparative in vitro study of frictional resistance between lingual brackets and stainless steel archwires

Abstract

Friction between archwires and labial brackets has received considerable attention; however, information on the frictional behaviour of commercially available lingual brackets is limited. The aim of this study was to investigate the frictional resistance resulting from a combination of lingual orthodontic brackets (7th Generation, STb, Magic, and In-Ovation L) and stainless steel archwires at 0, 5, and 10 degrees of second-order angulation. Each bracket type (n = 30) was tested with three different sizes of archwires. Static and kinetic frictional forces were evaluated with a universal testing machine. Statistical analysis of the data was performed with non-parametric Kruskal-Wallis and Dunn's multiple comparison tests. All tested brackets showed higher frictional forces as the wire size and second-order angulation increased. The lowest friction was found with In-Ovation L brackets and 0.016 inch archwires at 0 degrees angulation, and the greatest friction with a combination of STb brackets and 0.017 × 0.025 inch archwires at 10 degrees angulation. For all combinations, Magic and In-Ovation L brackets showed lower frictional resistance when compared with 7th Generation and STb brackets. The slot width (occluso-gingival dimension) of the brackets, measured using the optics of a microhardness machine, showed that all brackets were oversized and that Magic brackets had the largest slot width. Surface roughness of the brackets investigated using atomic force microscopy and scanning electron microscopy, demonstrated that the 7th Generation brackets had the greatest surface roughness.

In vitro assessment of competency for different lingual brackets in sliding mechanics

“…The archwire size and material has been standardized as 0.016″ × 0.022″ SS because it was widely used for space closure during sliding mechanics. [ 21 ] The archwires were cut into segments[ 17 ] of 25 cm each; two “U” shaped hooks (3.5 cm) were bent at the cut ends of the archwires. One was meant for hanging 200 g of counter weight[ 17 ] and the other was hooked to an acrylic block interface that was clamped to the movable upper crosshead arm.…”

“…[ 21 ] The archwires were cut into segments[ 17 ] of 25 cm each; two “U” shaped hooks (3.5 cm) were bent at the cut ends of the archwires. One was meant for hanging 200 g of counter weight[ 17 ] and the other was hooked to an acrylic block interface that was clamped to the movable upper crosshead arm. This pivoting joint like connection prevents any undue twist in the archwire during traction.…”

“…Friction in the perspective of ligation force and second order bracket angulations were extensively studied for labial brackets[ 2 3 4 5 6 7 8 9 10 11 12 13 14 15 ] but very few studies have been published on frictional behavior of lingual brackets[ 16 17 ] hence the aim and objectives of the present study are to evaluate and compare the frictional resistance of different lingual brackets at different second order angulations when coupled with stainless steel (SS) archwire in dry and wet conditions.…”

Wire Roughness Assessment of 0.016″ × 0.022″ the Technique Lingual Orthodontics

“…This allows good mechanical control because archwires of smaller caliber make it difficult to control the torque on anterior teeth, while larger caliber archwires, or those made of other metal alloys, such as nickel titanium or titanium molybdenum alloy, generating a large amount of friction in the retraction stage. 10,11,16 Topographical study of an orthodontic archwire surface is essential, because this property may have a strong influence on orthodontic mechanics. Rougher archwires induce greater friction and, therefore, retard dental movement.…”

“…[9][10][11] During sliding mechanics, the correct choice of brackets and archwires used is essential to obtain a better clinical result. Among the different factors to be evaluated, surface roughness of the orthodontic wire is primordial, since the increase in surface roughness may generate an increase in friction between the wire and bracket, thus leading to slower and less effective orthodontic treatment.…”