Scanning electron microscopy of cavity margins finished with ultra-speed instruments.

The quality of the margins of the box portions of Class II cavities finished with rotating instruments at ultraspeed was assessed. In a closed row of teeth, an adequate finish was obtained at the embrasure margin where the burs rotated toward the tooth surface and into the cavity. The finish of the opposite embrasure margin and of the gingival margin was imperfect, regardless of the instrument used.