Abstract
BackgroundThe aim of this study is to investigate the relative stiffness of straight and mushroom lingual archwires of different diameters, cross sections and alloys, plotting their load/deflection graphs and using a modified three-point bending test.MethodsFujita’s mushroom archwires and straight lingual archwires of different diameters, cross sections and alloys were derived by a virtual set-up of an equal malocclusion and were cut at their straight distal portion. These distal portions were tested using a modified three-point bending test by an Instron 4467 dynamometer and the forces, were exerted at 1-mm deflection and were compared on each resulting load/deflection curve by means of ANOVA (p < 0.05).ResultsAll upper lingual mushroom wires exerted significantly lower forces than the straight wire. Lower mushroom archwires were stiffer than their upper counterparts, which were longer and featured inset bends. In the lower arch, similar levels of forces were recorded for the two types of wire. Load-deflection curves were higher for the straight wires, and stiffness increased proportionally with their diameter.ConclusionsThe stiffness of an archwire is a function of its diameter, length and the alloy it is made from. In lower lingual wires, there is little difference in stiffness between mushroom and straight wires, but in upper wires, the straight version is considerably stiffer. The greater bearing effect exhibited by the straight wire in the working and finishing phases makes it less susceptible to bowing effect and therefore preferable for sliding mechanics during en masse retraction, particularly in the upper arch.
Highlights
The aim of this study is to investigate the relative stiffness of straight and mushroom lingual archwires of different diameters, cross sections and alloys, plotting their load/deflection graphs and using a modified three-point bending test
¥ For a given deflection, straight archwires exerted greater force with respect to mushroom wires (UMW and Lower lingual Muschroom Wire (LMW)) of the same section and alloy (Fig. 5). ¥ The difference between Upper lingual Muschroom Wire (UMW) and Upper lingual Straight wire (USW) in the force exerted at the same amount of deflection was statistically significant, but the difference between LMWs and Lower lingual Straight wire (LSW) did not always reach statistical significance (Table 3). ¥ All straight wires (SW) and MWs showed a tendency for the force exerted to increase with increasing archwire diameter. ¥ Titanium molybdenum alloy (TMA) wires are much softer than stainless steel wires (SS) and exert far less force
Lingual straight archwires should be preferred during frictional space closure by virtue of their major stiffness, capable to take under control bow side effects
Summary
The aim of this study is to investigate the relative stiffness of straight and mushroom lingual archwires of different diameters, cross sections and alloys, plotting their load/deflection graphs and using a modified three-point bending test. In 1995, the lingual orthodontics was revolutionised by Scuzzo and Takemoto’s lingual straight wire [3] As this technique evolved, new brackets with a lower profile (with shorter mesiodistal diameters and a thinner bracket pad) began to appear on the market, alongside new prescriptions and new straight wires (SW) designed for the lingual archform, squarer than the rounder version launched in the 1990s. New brackets with a lower profile (with shorter mesiodistal diameters and a thinner bracket pad) began to appear on the market, alongside new prescriptions and new straight wires (SW) designed for the lingual archform, squarer than the rounder version launched in the 1990s These innovations improved the reliability and speed of lingual orthodontics, not to mention patient comfort during the treatment [4]. One of the most important advantages of using the lingual straight wire technique is that sliding mechanics enable extraction spaces to be closed without the need for difficult modelling of the closing loop used in nonfrictional extraction space closure [3, 5]
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