OBJECTIVE: The purposes of this study were to measure the orthodontic forces generated by thermoplastic aligners and investigate the possible influences of different activations for lingual bodily movements on orthodontic forces, and their attenuation. METHODS: Thermoplastic material of 1.0-mm in thickness was used to manufacture aligners for 0.2, 0.3, 0.4, 0.5, and 0.6 mm activations for lingual bodily movements of the maxillary central incisor. The orthodontic force in the lingual direction delivered by the thermoplastic aligners was measured using a micro-stress sensor system for the invisible orthodontic technique, and was monitored for 2 weeks. RESULTS: Orthodontic force increased with the amount of activation of the aligner in the initial measurements. The attenuation speed in the 0.6 mm group was faster than that of the other groups (p < 0.05). All aligners demonstrated rapid relaxation in the first 8 hours, which then decreased slowly and plateaued on day 4 or 5. CONCLUSIONS: The amount of activation had a substantial influence on the orthodontic force imparted by the aligners. The results suggest that the activation of lingual bodily movement of the maxillary central incisor should not exceed 0.5 mm. The initial 4 or 5 days is important with respect to orthodontic treatment incorporating an aligner.
Incisor* ; Relaxation

Maxillary protaction is most commonly used for the treatment of growing skeletal class Ⅲ patients with a maxillary deficiency. The present article reviewed the advances in the use of maxillary protraction, including the case selection, the timing of the treatment, the effectiveness of rapid maxillary expansion, the pattern of the maxillary protraction and the long-term stability.

Objective To measure the orthodontic forces exerted on the upper right central incisor with the increase of the distance of tooth movement and the thickness of the aligner.Methods The labial movement of upper right central incisor at various distances (0.3,0.6,0.9,1.2,1.5,1.8 mm) was designed and the stereolithography model (2 times bigger than the original model) was created with 3-D scanning and tomography output.These models were used to fabricate the aligners with different thicknesses (0.8,1.0,1.5 and 2.0 mm) of the thermoplastic materials (6 samples for various distances of tooth movement and thicknesses).Orthodontic forces exerted on the upper right central incisor were measured with the micro-stress sensor measurement system.Results The orthodontic forces increased with the increase of the thickness of the aligner at the same distance of tooth movement (P ＜ 0.05).The orthodontic force was (1.237 ± 0.082),(1.543 ± 0.059),(3.602 ± 0.102),(6.734 ± 0.063) N when the labial movement of upper right central incisor was 0.3 mm with the aligner of 0.8,1.0,1.5,2.0 mm.The orthodontic forces also increased with the increase of the distance of the tooth movement at the same thickness of the aligner (P ＜ 0.05).The orthodontic force of the aligner of 0.8 mm were (1.354 ± 0.039),(1.288 ± 0.037),(1.479 ± 0.031),(1.799 ± 0.039) N when the upper right central tooth labial movement at 0.6,0.9,1.2,1.5 mm.Conclusions The orthodontic forces increased with the increase of the distance of tooth movement and the thickness of the aligner.

Orthodontic treatments have increasingly become accepted by adults. However, the treatment therapies and philosophies for adults and adolescents have numerous differences. Orthodontic treatment for adults requires more careful planning, flexible management, interdisciplinary cooperation, and rational expectations. New techniques, such as mini-screw implants, invisalign, and self-ligating brackets, have recently been used to update treatments and widen the application of adult orthodontics by improving the treatment results. However, orthodontists still face a number of risks and challenges.

Orthodontic treatments have increasingly become accepted by adults. However, the treatment therapies and philosophies for adults and adolescents have numerous differences. Orthodontic treatment for adults requires more careful planning, flexible management, interdisciplinary cooperation, and rational expectations. New techniques, such as mini-screw implants, invisalign, and self-ligating brackets, have recently been used to update treatments and widen the application of adult orthodontics by improving the treatment results. However, orthodontists still face a number of risks and challenges.
Adolescent ; Adult ; Humans ; Orthodontics

Objective:To compare the clinical efficacy of customized titanium plate and conventional maxillary protraction treatment in patients with skeletal class Ⅲ malocclusion during growth spurt.Methods:During growth spurt, skeletal class Ⅲ patients with maxillary hypoplasia who were treated in the Department of Orthodontics, Capital Medical University School of Stomatology from August 2018 to July 2021 were prospectively enrolled. They were treated with maxillary protraction using customized titanium plates (customized titanium plate group) and conventional methods (conventional protraction group), respectively. Lateral cephalometric radiographs were collected before and after treatment for conventional cephalometric analysis, including SNA angle (angle between Sella, Nasion and A point), ANB angle (angle between A point, Nasion, and B point), FH-MP angle (mandibular plane angle), Y-axis angle, U1-L1 angle (upper to lower central incisor angle), U1-SN angle (upper incisor to SN plane angle), anterior and lower height, maxillary length, etc. The stable basicranial line (SBL) was used as the reference line to measure the distance from each reference point (ANS point, A point, Prn point, Sn point, UL point etc.) to the stable basicranial vertical line (VerT, the perpendicular line of the skull base line at the intersection point of the anterior wall of the sella image and the inferior edge of the anterior bed process). Paired t-tests were performed on the cephalometric data before and after maxillary protraction treatment in the two groups, and two independent samples t-tests were performed to compare the differences in the efficacy of the two maxillary protraction methods. Results:A total of 20 patients (9 males and 11 females), aged (10.8±1.3) years, were included in the personalized titanium plate group. A total of 20 patients (8 males and 12 females), aged (10.5±1.1) years, were included in the conventional protraction group. The SNA angle, ANB angle, FH-MP angle, Y-axis angle, anterior lower height, maxillary length, ANS-VerT distance, A-VerT distance, Prn-VerT distance, Sn-VerT distance, and UL-VerT distance were significantly higher than those before treatment in the two groups ( P<0.05). The changes of SNA angle, ANB angle and A-VerT before and after treatment in the personalized titanium plate group [3.15°±2.28°, 4.64°±1.40°, (4.41±3.43) mm, respectively] were significantly higher than those in the traditional group [2.13°±2.69°, 2.81°±1.10°, (3.13±4.76) mm, respectively]( P<0.05), and the changes of U1-L1 angle and U1-SN angle before and after treatment (-0.76°±7.42° and 1.74°±6.38°, respectively) was significantly lower than that of the control group (-5.14°±6.62° and 4.57°±5.24°, respectively, P<0.05). Conclusions:Maxillary protraction can effectively improve skeletal class Ⅲ relationships in growing patients. The linear measurements using the SBL line as a reference plane visualize the sagittal improvement in sagittal relationship after maxillary protraction. The customized titanium plate maxillary protraction treatment has a clear therapeutic effect on patients with skeletal class Ⅲ deformities, and its dental effect is relatively small.