RESUMO
<p><b>OBJECTIVE</b>To investigate the stability of upper molars with the application of micro-screw implant anchorage during orthodontic treatment.</p><p><b>METHODS</b>Fifteen adult patients with severe maxillary protrusion were included. Upper first premolars were extracted and upper posterior anchorage was reinforced with micro-screw implant in all patients. The average treatment period to close the extraction space was 10.5 months. Cephalometric and cast analysis were carried out.</p><p><b>RESULTS</b>During the treatment, the micro-screw implants kept stable in sagittal plane; neither the mesial-distal movement nor the rotation or tipping of the upper molars during the treatment was of statistic significance (P > 0.05); the edge of upper incisors was retracted by 6.99 mm on average, and no significant vertical change was observed (P > 0.05).</p><p><b>CONCLUSIONS</b>Micro-screw implant could provide good anchorage control in the orthodontic treatment.</p>