Force decay of elastomeric ligatures: influence on unloading force compared to self-ligation.
OBJECTIVE
To compare elastomeric ligatures (EL) vs self-ligating (SL) brackets in terms of their effects on the unloading force of a 0.014-inch CuNiTi aligning wire.


METHODS
By simulating the alignment of a lingually malposed canine and using a full-arch design, three ligation methods -- SL, EL, and "relaxed" elastomeric ligature (REL) -- were tested with 30 wires per group. Each test was conducted in a dry field within a Plexiglas case at 35 +/- 2 degrees C. Eleven brackets were affixed from first molar to first molar site on a steel plate with a space created at the location of the left canine. The wire was deflected 3 mm then was unloaded at a speed of 2 mm per minute. Data were gathered from four points along the unloading plot generated during each test and then were compared by using the Kruskal-Wallis one-way analysis of variance. Mann-Whitney tests were used to compare combinations of groups.


RESULTS
Wires ligated with EL and REL produced an average unloading force equal to 56% and 88%, respectively, of the same wire in an SL bracket.


CONCLUSIONS
The unloading forces produced by a wire after force decay of the elastomers are not statistically different from the forces present in self-ligating systems.
Petersen
Alan
A
Department of Orthodontics, Saint Louis University, St Louis, MO, USA.
Rosenstein
Sheldon
S
Kim
Ki Beom
KB
Israel
Heidi
H
D003300:Copper; D003722:Dental Alloys; D003799:Dental Stress Analysis; D020724:Elastomers; D017276:Friction; D003765:Models, Dental; D009532:Nickel; D016382:Orthodontic Appliance Design; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D014025:Titanium
C415948:Copper NiTi; D003722:Dental Alloys; D020724:Elastomers; D003300:Copper; D009532:Nickel; D014025:Titanium