Accuracy of positioning three types of self-ligating brackets compared with a conventionally ligating bracket

The aim of this study was to determine whether the morphology of three different self-ligating brackets affects the accuracy of their positioning when compared with a conventionally ligating bracket.

An ex vivo prospective comparison of the accuracy of positioning self-ligating brackets with conventionally ligating brackets.

Orthodontic Department, Eastman Dental Institute, London, UK.

Twenty-five clinicians with 2 or more years experience of bracket placement bonded four identical typodont malocclusions with Damon MX(TM), In-Ovation System R(TM) and SmartClip(TM) self-ligating brackets and also Victory Series(TM) conventionally ligating brackets. Four hundred brackets of each type were positioned. Vertical, horizontal and angular bracket position errors were assessed by reference to the FA point and FACC respectively, using digital images and image analysis software.

Method error analysis showed no evidence of bias and minimal random error. The Victory Series brackets were the most accurately positioned. Although the amount of positioning error for all the self-ligating brackets was small, a greater number were positioned outside vertical and horizontal tolerance limits compared to the conventionally ligated brackets (P<0·001). The Damon MX bracket type was nearly 10 times more likely to be inaccurately placed relative to the FA point compared with the Victory Series bracket. The differences relating to angular positioning error were not statistically significant (P>0·05).

The findings indicate that the positioning of three types of self-ligating brackets was less accurate than the conventional pre-adjusted edgewise bracket, when using a direct bonding technique. This may have implications for their clinical application.