Galvanic corrosion of metal injection molded (MIM) and conventional brackets with nickel-titanium and copper-nickel-titanium archwires.
OBJECTIVE
To compare the galvanic coupling of conventional and metal injection molded (MIM) brackets with commonly used orthodontic archwires.


METHODS
Six of each type of bracket were suspended in lactic acid along with a sample of orthodontic wire (three nickel-titanium and three copper-nickel-titanium) for 28 days at 37 degrees C. The potential differences between the wires and brackets were recorded per second throughout the duration of the experiment.


RESULTS
The MIM brackets exhibited potential differences similar to those seen for the conventional brackets. The greatest potential difference was found for MIM brackets with nickel-titanium wires (512 mV), whereas MIM brackets with copper-nickel-titanium wires had the smallest difference (115 mV). Scanning electron microscope (SEM)-energy-dispersive spectroscopic analysis of the tie-wing area of each bracket type indicated similar elemental composition in both brackets, but in slightly different percentages by weight. The MIM bracket exhibited extensive internal porosity, whereas the conventional bracket was more solid internally.


CONCLUSIONS
The composition and manufacturing processes involved in fabricating MIM brackets impart corrosive properties similar to those seen in the bracket-wing area of conventional brackets and may provide a measurable benefit when taking into account the increased corrosion between the bracket and brazing alloy of conventional brackets.
Siargos
Barbara
B
Department of Orthodontics, Marquette University, Wisconsin, USA.
Bradley
Thomas G
TG
Darabara
Myrsini
M
Papadimitriou
George
G
Zinelis
Spiros
S
D003300:Copper / Q000737:chemistry*; D003343:Corrosion; D003722:Dental Alloys / Q000737:chemistry*; D004570:Electrogalvanism, Intraoral; D009532:Nickel / Q000737:chemistry*; D016910:Orthodontic Brackets; D009969:Orthodontic Wires; D013499:Surface Properties; D014025:Titanium / Q000737:chemistry*
C415948:Copper NiTi; D003722:Dental Alloys; C040654:titanium nickelide; D003300:Copper; D009532:Nickel; D014025:Titanium