Efficiency of the distal screw in the distal movement of maxillary molars.

Conventionally, noncompliance distal movement of molars relies exclusively on intraoral anchorage. The distal screw, a distal jet appliance supplemented by two paramedian mini-implants, is an innovative alternative. The aim of this study was to evaluate the suitability of this device to move molars bodily and distally.The effects of the distal screw were evaluated in a sample of 18 consecutively treated preadolescent and adolescent individuals (nine females and nine males; mean age at the start of treatment, 11.2 years). Two conical mini-implants (length 11.0 mm, diameter 1.5 to 2.2 mm) were placed in the anterior paramedian area of the palate of each patient. The coil springs of the device were activated to deliver a force of 240 cN per side. The dental and skeletal effects were investigated on pre- and posttreatment cephalometric radiographs.The distal screw produced a Class I occlusion of the first molars by moving them distally 4.7 mm, which is more than conventional appliances can accomplish. Although this took longer than conventional devices (9.1 months), it had the advantage of a roughly 2.1-mm premolar distal movement (ie, no anchorage loss as with traditional techniques).The distal screw anchored by two palatal mini-implants allows not only translatory molar distal movement, but also distal movement of the maxillary first premolars, thereby avoiding characteristic anchorage loss