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.

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In this study, three-dimensional modeling and finite element analysis were used to evaluate and compare the stability of Le Fort I osteotomy fixed with titanium and resorbable fixation systems under molar and incisor bite forces. A three-dimensional model of 5-mm advanced hemimaxilla was generated. Contact analyses between the upper and lower segments were prescribed. Two L-plates were inserted on this model via simulation. Displacement, principal stresses, and principal elastic strains were evaluated under 44-N, 125-N incisor and, 250-N molar bite forces. These results suggest that Le Fort I osteotomies fixed with titanium miniplates and screws were stable under all tested forces. However, in resorbable group, under incisor bite forces greater than 44 N, there is a great risk of plate fracture, screw deformation, and/or failure.

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Objective: To evaluate the biomechanical properties of a standard and a newly designed platescrew orthodontic anchorage system. Materials and Methods: A three-dimensional model of the posterior maxilla, including the zygomatic buttress region, was prepared. Insertion of standard and newly designed plates was simulated on the three-dimensional model. The effect of 200 g of orthodontic force on the plate, screws, and zygomatic bone was evaluated in three-dimensional models by finite element analysis. To determine the force distribution, Von Mises stress, principal maximum and minimum stress, and principal maximum and minimum elastic strain values were evaluated. Results: In all plate models the highest stresses occurred on the threaded bone site where the force application unit was attached. Conclusion: Changing the plate configuration did not affect the stress distribution in the newly designed plates. To equalize the force distribution, new plate designs that change the location of the force application unit are required.

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