Miniscrews for upper incisor intrusion.

The aim of this study was to investigate if true incisor intrusion can be achieved using miniscrews. Eleven patients (three males and eight females; mean age: 19.8 +/- 4.8 years) with normal vertical dimension showing a pre-treatment deep bite of 5.9 +/- 0.9 mm and a 'gummy' smile were enrolled in the study. After levelling of the maxillary central and lateral incisors with a segmental arch, an intrusive force of 80 g using closed coil springs was applied from two miniscrews placed between the roots of the lateral and canine teeth. The amount of incisor intrusion was evaluated on lateral cephalometric headfilms taken at the end of levelling (T1) and at the end of intrusion (T2). Statistical analysis of the data was performed using a paired t and Wilcoxon signed rank tests. A significance level of P < 0.05 was predetermined. The mean upper incisor intrusion was 1.92 mm and the mean overbite decrease 2.25 +/- 1.73 mm in 4.55 months. Upper incisor angulation resulted in a 1.81 +/- 3.84 degree change in U1-PP angle and a 1.22 +/- 3.64 degree change in U1-NA angle. However, these were not statistically significant (P > 0.05). True intrusion can be achieved by application of intrusive forces close to the centre of resistance using miniscrews. However, studies with a larger number of subjects and long-term follow-up are necessary.