Treatment effects and anchorage potential of sliding mechanics with titanium screws compared with the Tweed-Merrifield technique

The purposes of this study were to quantify the treatment effects of titanium screws on en-masse retraction of 6 anterior teeth and to compare the anchorage potential of treatment with titanium screws with the Tweed-Merrifield technique, which requires patient compliance with a high-pull J-hook. Sixteen nongrowing patients (14 women, 2 men; ages, 22.5 ± 4.8 years) who had been treated orthodontically for bialveolar protrusion were selected. All patients had 2 maxillary first premolars extracted, 13 had mandibular first premolars extracted, and 3 had second premolars extracted. Maxillary titanium screws were placed in all patients to provide anchorage for retraction of 6 anterior teeth. Screws were placed in 8 patients to apply intrusive force to the mandibular posterior teeth. To compare the anchorage potential with a high-pull J-hook, 14 nongrowing patients (11 women, 3 men; ages, 22.9 ± 4.0 years) who were treated with the Tweed-Merrifield technique and had an excellent compliance with a high-pull J-hook were used. There was more anchorage loss of the maxillary posterior teeth in the Tweed-Merrifield group than in the titanium screw group. Both groups had excellent vertical control of the maxillary posterior teeth. There was a skeletal effect on the maxilla—reduction of A-point in the titanium screw group; this contributed to improvement of the facial profile. Treatment time in the titanium screw group was less compared with the Tweed-Merrifield technique. The success rate for the titanium screws was 87% in 25.6 ± 5.5 months. These results suggest that titanium screws can provide acceptable and reliable anchorage and might produce skeletal effects on the maxilla.