Fracture of polycarbonate edgewise brackets: a clinical and SEM study.

Fracture experience and fracture form of polycarbonate edgewise brackets, were assessed in a clinical study using four force controlled mechanical systems. The incidence and types of bracket fracture were investigated macroscopically and by Scanning Electron Microscopy (SEM). It was concluded that the engagement of both round and square archwires and stainless steel ligaturing were aetiological factors in bracket fracture.