The effect of timing of archwire placement on in vivo bond failure

At the commencement of fixed appliance therapy the operator has the choice of either placing bands, brackets, and archwires at one visit, and hence loading the brackets within an hour of initial placement, or placing the brackets and separators at one visit, and the bands and archwires at a subsequent visit. In the case of the latter, the brackets will only be loaded intermittently during the intervening period, for example during mastication. The present study investigated the effect of loading bonded brackets for 2 weeks prior to measuring shear debonding force in vitro, and compared the results with in vivo bond failure rates for two groups of patients whose brackets were loaded by the archwire either immediately after bonding, or not less than 1 week later. Shear testing and survival analysis indicated in vitro loading prior to testing had no significant effect on the shear debonding force. When the in vivo data were studied there was no significant difference in the rate of bond failure between those patients whose archwires were placed at the time of fitting the appliance, and those whose archwires were placed no less then 1 week after bracket placement.