OBJECTIVETo compare the regional load deflection rate (LDR) of multiloop edgewise arch wire (MEAW) of three dimensions with coupled use of two dimension brackets in the individual interbracket span, to understand the mechanical properties of MEAW.

METHODSThe MEAW arch wires of stainless steel of three dimensions, 0.41 mm x 0.56 mm, 0.43 mm x 0.64 mm and 0.46 mm x 0.64 mm, were bent into single L-loop. The study was performed with the coupled use of 0.41 mm x 0.56 mm wires with 0.46 mm x 0.64 mm bracket (A bracket) and 0.43 mm x 0.64 mm, 0.46 mm x 0.64 mm wires with 0.56 mm x 0.71 mm bracket (B bracket). The LDR of each L-loop at the individual interbracket span when loading and unloading was measured. The data were analysed by SPSS 11.0.

RESULTSCompared the regional LDR for the couple of 0.41 mm x 0.56 mm L-loop with A bracket with those for the couple of 0.43 mm x 0.64 mm L-loop with B bracket, the former showed lower value than the latter at regions between the upper central and lateral incisor, the lower central and lateral incisor, and between the lower lateral incisor and canine (P < 0.05). For the rest regions, the two couples exhibited similar value to the regional LDR (P > 0.05). The regional LDR for the couple of 0.41 mm x 0.56 mm L-loop with A bracket were lower at all regions than those for the couple of 0.46 mm x 0.64 mm L-loop with B bracket (P < 0.05) except that at the region between the lower first and second molars which showed similar value between the two couples.

CONCLUSIONThe coupled use of B bracket with 0.43 mm x 0.64 mm MEAW arch wire and A bracket with 0.41 mm x 0.56 mm MEAW arch wire exhibited similar mechanical properties.