Frictional resistance between Begg and Tip-Edge brackets and archwires

Abstract

The present in vitro study aims to measure the frictional resistance between Begg and Tip Edge brackets and some commonly used arch wire combinations. The combinations simulated the various stages in the Begg and Tip Edge technique. A testing apparatus was specially designed to measure the dynamic frictional resistance of both the metal and ceramic Begg and Tip Edge brackets. This apparatus creates second order deflections to be offset from 0.00mm to 0.75mm in increments of 0.25mm. Two pairs of brackets are aligned vertically at the 0.00mm offset initially and the arch wire is connected to the brackets with either lock pins in Begg brackets or steel ligatures and elastomeric modules in Tip Edge brackets. The arch wires included Australian Wilcock stainless steel wires, nickel-titanium wires and TP Co-Ax@ braided stainless steel wires. An Instron Universal testing machine is used to slide the wire through the brackets at a rate of 5mm/min for a period of 2 minutes with measurements plotted on a computer. Each combination was tested 3 times. Each set of combinations was first tested in a dry environment and then again tested after lubrication with artificial saliva (wet environment). A total of 50 combinations were tested. The data were analyzedwith arepeated measures analysis of variance testing the main effects of l) arch wire/bracket combinations, 2) environment, 3) deflections and 4) method of ligation, The level of significance was predetermined at p<0.01. Begg Stage I with Co-Ax@ wire produced the lowest friction while the Australian stainless steel produced the highest frictional resistance with the ribbon arch brackets. A wet environment with artihcial saliva signihcantly increased the frictional resistance with only the metal Begg bracket. Steel ligatures produced a signihcantly higher frictional resistance than elastomeric modules with the metal Tip Edge bracket. At higher deflections, Stage III with rectangular wire produced higher frictional resistance than with round wires. An increase in deflection increased the frictional resistance in all the brackets tested. It should be recognized that since there are many variables affecting friction in the various bracket and arch wire combinations, it is difficult to design an in vitro study and extrapolate its findings to an in vivo or clinical situation.