Distal Movement Research Articles

An Innovative and Conservative Approach to Molar Distalization

ABSTRACT Nonextraction approach in correcting Class II malocclusion has gained a lot of attention over the past few years. Clinicians prefer intraoral appliances as compared to extraoral appliances to achieve distal molar movement; the reason being intraoral appliances depends minimally on patient cooperation. In this article, a case report was presented in which a patient was treated with modified rapid maxillary expander, a concept designed from Veltri distalizer considering its advantages. Molar distalization of 4 mm was achieved with minimal anchorage loss on premolars and anteriors. Class I molar, canine relation was achieved with 2 mm of overjet and overbite. Modified appliance when used at appropriate timing was found to be an effective and conservative approach in distalization of maxillary first molars.

Influence of maxillary molar distalization with clear aligners on three-dimensional direction: molar distal movement, intrusion, distal tip and crown buccal torque

BackgroundThe aim of this study was to evaluate the distal movement, vertical movement, distal tipping and crown buccal torque of maxillary molars after the completion of distalization by comparing the predicted movement with the achieved movement using palatal rugae registration.MethodsThe study included 22 clear aligner patients (7 males and 15 females), and 79 molars were measured. Two digital models were generated before treatment and after molar distalization and were superimposed after selecting the palatal rugae area for registration in GOM inspect suite software 2022 (GOM; Braunschweig, Germany). The predicted and achieved movements of molar distalization, intrusion, distal tip and crown buccal torque were measured and compared.ResultThe achieved distalization (1.25 ± 0.79 mm vs. 2.17 ± 1.03 mm, P < 0.001; 1.41 ± 1.00 mm vs. 2.66 ± 1.15 mm, P < 0.001), intrusion (0.47 ± 0.41 mm vs. 0.18 ± 0.54 mm, P < 0.01; 0.58 ± 0.65 mm vs. 0.10 ± 1.12 mm, P < 0.01), distal tip (5.30 ± 4.56° vs. 1.53 ± 2.55°, P < 0.001; 4.87 ± 4.50° vs. − 1.95 ± 4.32°, P < 0.001) and crown buccal torque (1.95 ± 4.18° vs. − 1.15 ± 4.75°, P < 0.001; 0.43 ± 4.39° vs. − 4.27 ± 6.42°, P < 0.001) were significantly different from the predicted values in the two groups (first molar, second molar). Significant regression relationships were found between the achieved distal movement and deviational intrusion (R2 = 0.203, P < 0.0001), distal tip (R2 = 0.133, P < 0.001) and crown buccal torque (R2 = 0.067, P < 0.05). There was a significant correlation between the deviational movements of intrusion and the distal tip (R = 0.555, P < 0.0001).ConclusionApproximately 2 mm maxillary molar distalization was achieved in this study. Deviational movement of intrusion, distal tip and crown buccal torque beyond the clear aligner virtual design appeared to a certain degree after distalization. Thus, more attention should be given to molar intrusion and distal tip and crown buccal torque as the designed distalization increases.

Cervical headgear effectiveness in distalizing molars in relation to patient compliance.

The purpose of this study was to measure the effectiveness of the cervical headgear for distalizing first permanent maxillary molars in relation to hours of use. This was a one-centre, prospective, clinical study conducted at the Department of Orthodontics, School of Dentistry, National and Kapodistrian University of Athens, Athens, Greece. Participants (N = 26; 17 females, 9 males) were patients with no history of orthodontic treatment, no syndromes or clefts, and Angle's Class II malocclusion, where the treatment plan included a cervical headgear. They were instructed to wear the appliance for at least 12 h per day. A TheraMon® microsensor was embedded in the headgear's strap to objectively measure wear-time. To measure tooth movement, pre- and post-treatment digital models were superimposed, using the palate as a reference area; translation and rotation were measured along three axes. Superimposition and movement measurements were made with the Viewbox 4 software. Average treatment time and headgear wear were 130 days and 55 days, respectively, i.e. 10.1 h/day. During this period, distal movement averaged 1.75 mm with high variability (min 0.2 mm, max 4.5 mm). Distal tipping and rotation had an average of approximately 5 °C. Cumulative headgear wear was significantly correlated with distal movement (r2 = 0.32, P < .002), distal tipping (r2 = 0.27, P < .01), and distal rotation around the long axis of the tooth (r2 = 0.20, P < .05). Compliance is critical for having a successful clinical outcome. Distalization of the molar with a cervical headgear is correlated with the cumulative hours of appliance use, with hours per day being a weaker predictor.

Three-dimensional measurement and analysis of Mandibular Molar Distalization assisted by micro-implant anchorage combined with clear aligner.

To investigate the effect of micro-implant anchorage combined with a clear aligner on the efficiency of mandibular molar distalization and the protection of anterior teeth anchorage, provide reference for clinical scheme design. This is a prospective study. Seventeen patients who were treated in the Orthodontics Department of the Hospital of Stomatology affiliated to Fujian Medical University from 2019 to 2021 and used Invisalign clear aligners to move mandibular molars distally were included and divided into two groups according to anchorage types: Group-A and Group-B. Group-A (ten cases) were treated without micro-implant anchorage, while Group-B (seven cases) were treated with micro-implant anchorage nails for enhanced anchorage. The effect of micro-implant anchorage on crown and root distal movement of mandibular molars and the difference in three-dimensional movement between mandibular molars and mandibular central incisors were analyzed. The crown distalization efficiency of mandibular first and second molars in Group-B was 68.66% and 71.02%, respectively, which were higher than those in Group-A(p<0.05). The mandibular central incisors in Group-A showed labial displacement and a small amount of elongation, while those in Group-B showed less anchorage loss(p<0.05). In Group-A, the crown was tilted in the distal direction and moved in the buccal direction during mandibular molar distalization(p<0.05). While in Group-B, the crown was tilted in the distal directio (p<0.05) and the mandibular second molar was depressed(p<0.05). In the process of mandibular molar distalization assisted by micro-implant anchorage combined with a clear aligner, better protects the anchorage of the mandibular central incisor and improves the efficiency of the molar crown distalization.

Vertical changes in the hard tissues after space closure by miniscrew sliding mechanics: a three-dimensional modality analysis

ObjectivesThis study aimed to investigate vertical changes in the maxillary central incisor and the maxillary first molar, along with alterations in the mandibular plane angle during space closure using miniscrew sliding mechanics.MethodsTwenty adult patients treated at Peking University Hospital of Stomatology between 2008 and 2013 were included. Digital dental models and craniofacial cone-beam computed tomography (CBCT) scans were obtained at the start of treatment (T0) and immediately after space closure (T1). Stable miniscrews were used for superimposing maxillary digital dental models (T0 and T1), and vertical changes in the maxillary first molar and the maxillary central incisor were measured. Three-dimensional changes in the mandibular plane were assessed through CBCT superimposition.ResultsThe maxillary central incisor exhibited an average extrusion of 2.56 ± 0.18 mm, while the maxillary first molar showed an average intrusion of 1.25 ± 1.11 mm with a distal movement of 0.97 ± 0.99 mm. Additionally, the mandibular plane angle decreased by an average of 0.83 ± 1.65°. All three indices exhibited statistically significant differences.ConclusionDuring space closure using the miniscrew sliding technique, significant changes occurred in both the sagittal and vertical dimensions of the upper dentition. This included extrusion of the maxillary central incisors, intrusion of the maxillary first molars, and a slight counterclockwise rotation of the mandibular plane.

Three-dimensional finite element analysis of the uprighting movement of mandibular mesially inclined second molars

The mesially inclined mandibular second molar can be supported upright by the microimplant anchorage. This study established the finite element model to analyze the displacement trend and periodontal ligament (PDL) stress distribution of the uprighting mandibular second molar with the microimplant under different conditions. A 3-dimensional model of the mandible and dentition was established. The mesial inclination of the mandibular second molar was 30°, 45°, and 60°. Microimplants were implanted between the buccal side of the second premolar and the first molar and in the distal part of the mandibular second molar, respectively. Six groups were set, each loaded with 0.5 N of force. The second molar initial displacement trend and PDL stress distribution were evaluated. The PDL stress of mandibular second molars in all groups was within the physiological limit, and the PDL stress of mandibular second molars in the distal implant groups was lower than that of mandibular second molars in the mesial implant groups. PDL stress concentration in the cervical area. Tooth displacement decreased as the mesial inclination angle of the second molars increased. The sagittal displacement of mesial implant groups was larger, and there was a tendency of mesiobuccal torsion when standing uprighting; the vertical displacement of distal implant groups was larger, and there was a tendency of distal lingual torsion when standing uprighting. Distal microimplant has a better extrusion effect on the mesially inclined second molar, whereas mesial microimplant has a better effect on the distal movement. The optimal orthodontic force for microimplant traction on mesially inclined second molars is 0.5-0.8 N.

Factors influencing the efficacy of invisalign in molar distalization and tooth movement.

Introduction: The work aims to establish and analyze the factors influencing the efficacy of Invisalign in molar distalization and tooth movement. Objectives of the study: 1) identify factors contributing to molar distalization and tooth movement; 2) analyze the effectiveness of Invisalign technology in molar distalization and tooth movement. Methods: The study was conducted in 2020-2022 in Baoding (PRC) based on Baoding's first central hospital. Forty patients (mean age 28.5 ± 1.5 years, 18-35 years; 20 women and 20 men) participated in the study. Results: All patients had mild to moderate degrees of tooth crowding, with an angle class II malocclusion, as well as maxillary third molars. Before and after the therapy, the condition of the alveolar bone, soft tissues, and facial height were measured. Fixation of the anterior teeth was performed. Calculations of the distal molar movement were performed. For orthodontic procedures, the secondM of the upper jaw were moved, and then the first molars were moved. Discussion: Distalization of the upper molars was found to be an effective movement, with an efficiency of about 83% when vertical rectangular attachments were used. The first molar was moved distally by 2.85mm without significant tilt or movement in the vertical plane.

Effective contribution ratio of the molar during sequential distalization using clear aligners and micro-implant anchorage: a finite element study

IntroductionThis study aims to investigate the biomechanical effects of anchorage reinforcement using clear aligners (CAs) with microimplants during molar distalization. And also explores potential clinical strategies for enhancing anchorage in the sequential distalization process.MethodsFinite element models were established to simulate the CAs, microimplants, upper dentition, periodontal ligament (PDL), and alveolar bone. In group set I, the 2nd molars underwent a distal movement of 0.25 mm in group set II, the 1st molars were distalized by 0.25 mm after the 2nd molars had been placed to a target position. Each group set consisted of three models: Model A served as the control model, Model B simulated the use of microimplants attached to the aligner through precision cuts, and Model C simulated the use of microimplants attached by buttons. Models B and C were subjected to a series of traction forces. We analyzed the effective contribution ratios of molar distalization, PDL hydrostatic stress, and von Mises stress of alveolar bone.ResultsThe distalization of the 2nd molars accounted for a mere 52.86% of the 0.25-mm step distance without any reinforcement of anchorage. The remaining percentage was attributed to the mesial movement of anchorage teeth and other undesired movements. Models B and C exhibited an increased effective contribution ratio of molar distalization and a decreased loss of anchorage. However, there was a slight increase in the undesired movement of molar tipping and rotation. In group set II, the 2nd molar displayed a phenomenon of mesial relapse due to the reciprocal force produced by the 1st molar distalization. Moreover, the efficacy of molar distalization in terms of contribution ratio was found to be positively correlated with the magnitude of force applied. In cases where stronger anchorage reinforcement is required, precision cuts is the superior method.ConclusionsThe utilization of microimplants in conjunction with CAs can facilitate the effective contribution ratio of molar distalization. However, it is important to note that complete elimination of anchorage loss is not achievable. To mitigate undesired movement, careful planning of anchorage preparation and overcorrection is recommended.

Dentoalveolar and Soft Tissue Changes Following en-Masse Anterior Retraction With Different Force Vectors in Subjects With Bidental Protrusion: A Retrospective Evaluation.

Introduction The aim of the study is to determine the effects of different vertical force vectors acting on dentoalveolar and soft tissues while applying a retraction force using various anchorage sources and their effects on these tissues. Material andmethods Based on the selection criteria, a total of 35 patient case records with Angle's Class I bidental malocclusion and incompetent lips treated with four premolar extractions were included. Retraction was achieved using a NiTi coil spring with two different force vectors. The anchorage in group 1 was enhanced by a transpalatal arch (TPA)and Lower Stabilizing Arch(LSA) in the upper and lower arch, respectively, with a force vector parallel to the occlusal plane,whereas in group 2, the force vector using Temporary Anchorage Devices (TADs) was 15 - 20 degrees to the occlusal plane. The skeletal, dental, and soft tissue were obtained using 40 parameters. Intra-group comparisons between pre- and post-treatment records were conducted using a paired t-test, while inter-group comparisons were conducted using an independent t-test. Result Significant anchor loss was observed in group 1, indicated by mesial movement of molar crowns by (-2.10±0.50) in the maxillary arch and (-1.75±0.38) in the mandibular arch. Distal movement of incisors following premolar extractions with both studied force vectors resulted in an improvement in lip procumbency and incisor inclinations, without any significant skeletal changes.Molar mesial movement was observed in subjects treated with conventional anchorage. Conclusion En masse anterior retraction did lead to anchorage loss when carried out without TADs.Altering the force vector did not produce significant changes in tooth movement along the vertical plane.

Effects of three types of attachments in the displacements, and distribution of stress and plastic deformation, and trough finite elements (FEM)

Objectives: The aim of the study was to evaluate the effect of resin attachments on the displacement and deformation pattern of the aligner plastic, determine the center of rotation and stress distribution in the upper canine during space closure using the finite element method (FEM), and evaluate the plastic Aligner deformation. Materials and Method s: A computer-assisted design model of the superior right hemiarch was constructed with the simulation of a first premolar extraction and a canine distalization, recreating the periodontal ligament and alveolar bone. FEMs were created to analyze the behavior of stress and displacement of the upper right canine with aligners in four situations, one without attachment, and three with bonded attachments (vertical rectangular, rectangular beveled, optimized root control). In addition, the plastic deformation of the aligner was evaluated. Results: In the simulation without attachment, there was no apical movement, while with vertical rectangular and rectangular beveled the behavior was similar with crown distal displacement and mesial apex displacement. The optimized attachment had a better movement control of the canine body respecting the crown and apical movement toward the same direction. The mayor plastic deformation was shown without attachment and no deformation was evidenced with optimized attachment. Conclusion: The FEM showed that nevertheless the optimized attachment produced a distal crown and apical displacement with the use of plastic aligners during the space closure, the apex only moved ¼ of the distal crown movement. Our results suggest that to obtain a pure translation of the canine with aligners, it would be necessary the use of auxiliars which complement the needed biomechanics.

Effect of applying intermittent force with and without vibration on orthodontic tooth movement.

This study aimed to determine whether orthodontic tooth movement could be accelerated by applying an intermittent force protocol. It also examined the effect of applying additional vibrational forces on orthodontic tooth movement and root resorption rates. This study included 24patients (16males and 8females) who underwent orthodontic treatment involving first premolar extraction and distal movement of the canines in the maxilla.A Hycon device (Adenta GmbH, Gilching, Germany) was used for canine distalization in all patients. The patients were randomly divided into two groups: one group received 20 min of vibration per day using the AcceleDent device (OrthoAccel Technologies, Inc., Bellaire, TX, USA), while the other group received no vibration. In addition, asplit-mouth design was used: an activation-only force protocol was applied on one side, and an intermittent activation-deactivation-activation (ADA) protocol was applied on the other. The duration required for complete canine tooth distalization on each side was calculated. In addition, the effect of vibration on the orthodontically induced root resorption was examined. The intermittent ADA protocol significantly accelerated orthodontic tooth movement compared to the activation-only protocol (p < 0.05). The application of additional vibration did not affect the orthodontic tooth movement rate (p > 0.05). Using aHycon device and following an ADA protocol provided significantly faster canine distalization than the activation-only protocol (p < 0.05). This intermittent force method proved very effective in closing the spaces. However, vibration did not significantly affect the orthodontic tooth movement rate (p > 0.05).

Three-dimensional finite element study of mandibular first molar distalization with clear aligner.

This study aimed to construct the finite element model of the mandibular first molar with the invisible appliance and explore the dentition movement characteristics of the mandibular first molar when using micro-implant anchorage and different initial positions of the first molar. Models of the mandible, tooth, periodontal membrane, and invisible appliance were constructed using cone beam computed tomography (CBCT) data. The two groups were divided into the non-anchorage group and the micro-implant group (between the roots of the first molar and the second molar) based on whether the elastic traction of the micro-implant was assisted or not. The two groups were divided into the following conditions based on the starting position of the first molar: Working condition 1: the distance between the first molar and the second premolar was 0 mm; working condition 2: the distance between the first molar and the second premolar was 1 mm; working condition 3: the distance between the first molar and the second premolar was 2 mm; working condition 4: the distance between the first molar and the second premolar was 3 mm. The data characte-ristics of total displacement and displacement in each direction of dentition were analyzed. In the non-ancho-rage group, all the other teeth showed reverse movement except for the first molar which was moved distally. Meanwhile, in the micro-implant group, except for a small amount of mesial movement of the second molar in wor-king condition 1, the whole dentition in other working conditions presented distal movement and anterior teeth showed lingual movement, among which the distal displacement of the first molar in working condition 4 was the largest. With the change of the initial position of the first molar to the distal, the movement of the first molar to the distal, the premolar to the mesial, and the anterior to the lip increased, while the movement of the second molar to the mesial decreased. The micro-implant can effectively protect the anterior anchorage, increase the expression rate of molar distancing, and avoid the round-trip movement of the second molar. The initial position of the first molar movement is related to the amount of distancing and the remaining tooth movement.

Using digital image correlation to measure displacement and strain during involving distal movement of anterior teeth with clear aligner.

To investigate methods to suppress the bowing effects of lingual inclination and anterior tooth extrusion, digital image correlation (DIC) was used to evaluate aligner displacement in three-dimensions through comparing the distal movement of six and four anterior teeth. Computed tomography scans were used to measure aligner thickness and shape. Based on displacement direction and magnitude, a desirable deformation mode with minimal lingual inclination and extrusion was observed during distal movement of four anterior teeth. The aligner had a rigid "constriction zone" between the lateral incisor and the canine, facilitating control localized to the anterior teeth and minimizing the reaction of the molars. The mechanical behavior of aligners was greatly affected by the method of anterior teeth movement and the shape of aligners. DIC-based displacement measurements are useful in investigating correction directionality.

Empirical Myoelectric Feature Extraction and Pattern Recognition in Hemiplegic Distal Movement Decoding.

In myoelectrical pattern recognition (PR), the feature extraction methods for stroke-oriented applications are challenging and remain discordant due to a lack of hemiplegic data and limited knowledge of skeletomuscular function. Additionally, technical and clinical barriers create the need for robust, subject-independent feature generation while using supervised learning (SL). To the best of our knowledge, we are the first study to investigate the brute-force analysis of individual and combinational feature vectors for acute stroke gesture recognition using surface electromyography (EMG) of 19 patients. Moreover, post-brute-force singular vectors were concatenated via a Fibonacci-like spiral net ranking as a novel, broadly applicable concept for feature selection. This semi-brute-force navigated amalgamation in linkage (SNAiL) of EMG features revealed an explicit classification rate performance advantage of 10-17% compared to canonical feature sets, which can drastically extend PR capabilities in biosignal processing.

Enriched Rehabilitation Reduces Abnormal Motor Synergies and Enhances Motor Plasticity Following Severe Stroke in Rats.

Stroke results in loss of upper motor neuron control over voluntary movements and emergence of abnormal synergies. Presently, it is unclear to what extent poststroke recovery reflects true recovery (restitution), compensation, or some combination of these processes. Here, we investigated this question using behavioral and kinematic analyses of skilled reaching in rats subjected to severe stroke that affected both the forelimb motor cortex and dorsolateral striatum. After stroke, male rats either spontaneously recovered or received enriched rehabilitation. We assessed forelimb motor recovery using behavioral and kinematic outcome measures. To provide insights into the mechanisms underlying the effects of rehabilitation on behavior, we used intracortical microstimulation and FosB (protein fosB) immunostaining techniques. Enriched rehabilitation significantly improved food pellet retrieval in the staircase-reaching task. Rehabilitation resulted in several poststroke flexion synergies returning to prestroke patterns, and across subjects, these changes correlated with the intensity of rehabilitation. Enriched rehabilitation increased the proportion of distal movement representation in the perilesional cortex and increased use-dependent activation in the ipsilesional red nucleus. These results provide evidence that enriched rehabilitation enhances recovery, at least in part, by restitution of forelimb function following severe stroke. Furthermore, the restitution of function is associated with changes in multiple motor-related structures at different levels of the central nervous system. A better understanding of the processes that underlie improved motor performance, along with the identification of midbrain circuits activated by rehabilitation, represent new insights and potential targets for optimizing poststroke recovery.

EFFECTS OF 2x4 APPLIANCE AND NiTi OPEN SPRING ON MIXED DENTITION

Background/Objectives: The mixed dentition period is the best time to guide the occlusion and intercept a malocclusion. Among the preventive orthodontic procedures, space recovery is considered extremely important for the biogenesis of the occlusion to follow its normal course. Several orthodontic appliances indicated for space recovery in mixed dentition are mentioned in the literature and among them, mechanics with a fixed 2x4 partial appliance.This study aimed to evaluate changes in the dimensions of the upper arch after using a 2x4 fixed partial appliance with expanded CuNiTi wires and open NiTi springs. Material and Methods: Twenty-four children (±9 years) were assessed who had no space for the eruption of permanent teeth in the upper arch, treated with a 2x4 fixed partial appliance. Lateral teleradiography imaging, panoramic radiography and cast models were used before and after the treatment. The results were compared to a control group of 24 children who did not receive treatment and had their documents assessed for growth-related changes. The following changes were evaluated: dimension of arch perimeter, arch depth, intermolar distance, and inclination and displacement of permanent upper molars and incisors. Student’s t-test was used to assess the differences between pre- and post-treatment times, with significance level of 5%. Results: Increases were observed in arch perimeter (p=0) and arch depth (p=0) due to a distal movement of the crown (p=0) and the root of molars (p=0.004), and maintenance of the spatial position of the incisors, without protrusion (p=0.37) or vestibular movement (p=0.13). Limitations: the limitation of the present study was not to randomize the sample and not to use a control group identical to the group that received treatment. Conclusion: 2x4 fixed partial appliance was effective for the recovery of mixed dentition space, increasing the arch perimeter and depth through a distal movement of the upper molar and maintenance of incisor position.

Comparison of the Bone-Anchored Pendulum Appliance and the Bone-Anchored Intraoral Bodily Molar Distalizer: An Original Research.

With the advent of mini-implants, Class II correction has become routine. The study's goal was to compare the "Bone-Anchored Pendulum Appliance (BAPA)" to the "Bone-Anchored Intraoral Bodily Molar Distalizer (BAIBMD)" in terms of clinical efficacy. Five boys and five girls were among the 10 patients in this split-mouth trial who had to have their molars distalized. On one side, BAPA Construction, and on the other, BAIBMD was piloted. A titanium mini-screw was used to secure both appliances to the bone since this was a spilled-mouth technique. The first molar bands to apply 200 g of force were used for both devices, as with all the other components that were similar for both appliances. For both sides, the nature, duration, and rate of tooth movement were compared. Using the Wilcoxon signed-rank test, descriptive statistics for several parameters were examined. Distalization was accomplished on both sides with clinical success. The rate of distalization did not show any significant variation. Less time was needed for distalization with BAPA, as evidenced by the statistically substantial variances in treatment duration between the two groups. Molar tipping was noticed in BAPA, and it was statistically significant. While the pace of distalization was equal for both appliances, BAIBMD required more time than BAPA but resulted in a distal tooth movement that was mostly translatory in nature.

The identification of possible reference planes on a CBCT scan taken with a small FOV—an observational analytical study

Abstract Objectives Unlike a CBCT scan which has a large field of view (FOV), a scan with a small FOV may not involve the base of the skull. Therefore, routinely used reference planes may not be available to evaluate treatment outcome. The present study was undertaken to determine if the palatal plane and a molar occlusal plane may be used as reference planes to measure the change in the axial inclination of the maxillary central incisor and the maxillary first permanent molar towards the end of orthodontic treatment on a CBCT scan captured with a small FOV. Materials and methods A lateral cephalogram and a CBCT scan with a small FOV were taken for fifteen young adults prior to, and six months after, mini-implant supported, distal movement of the maxillary arch. CBCT multi-planar slices were sequentially viewed to obtain an image that contained the entire length of the maxillary central incisor and the maxillary first permanent molar in the tangential view. The axial inclination of the maxillary central incisor and the maxillary first permanent molar was measured from the palatal plane and the molar occlusal plane on both sides. The same parameters were evaluated on the lateral cephalogram using the palatal plane as a reference. An independent t test (p = 0.05) was conducted to compare the results. A Bland–Altman plot with linear regression was constructed to measure accuracy, method agreement and reliability. Results There was no statistically significant difference when a change in the axial inclination of the maxillary central incisor and the maxillary first permanent molar was measured using the two reference planes. The change in axial inclination of the maxillary central incisor and maxillary first permanent molar had a 95% confidence interval of -1.82 to 4.19 and -4.48 to 3.05 and a p-value of 0.425 and 0.701 on the right side, respectively, and a 95% confidence interval of -1.76 to 4.79 and -4.41 to 2.79 and p-value of 0.350 and 0.650 on the left side. Conclusions The molar occlusal plane and the palatal plane may be used as reference planes for measuring change in the axial inclination of the maxillary central incisor and the first permanent molar in a CBCT scan taken with a small FOV.

Three-dimensional changes after maxillary molar distalization with a miniscrew-anchored cantilever.

To evaluate the changes after maxillary molar distalization in Class II malocclusion using the miniscrew-anchored cantilever with an extension arm. The sample included 20 patients (9 male, 11 female; mean age 13.21 ± 1.54 years) with Class II malocclusion, treated with the miniscrew-anchored cantilever. Lateral cephalograms and dental models obtained before (T1) and after molar distalization (T2) were evaluated using Dolphin software and 3D Slicer. Superimposition of digital dental models using regions of interest on the palate was performed to evaluate three-dimensional displacement of maxillary teeth. Intragroup change comparisons were performed using dependent t-test and Wilcoxon test (P < 0.05). The maxillary first molars were distalized to overcorrected Class I. The mean distalization time was 0.43 ± 0.13 years. Cephalometric analysis demonstrated significant distal movement of the maxillary first premolar (-1.21 mm, 95% confidence interval [CI]: -0.45, -1.96) and maxillary first (-3.38 mm, 95% CI: -2.88, -3.87) and second molars (-2.12 mm, 95% CI: -1.53, -2.71). Distal movements increased progressively from the incisors to the molars. The first molar showed small intrusion (-0.72 mm, 95% CI: 0.49, -1.34). In the digital model analysis, the first and second molars showed a crown distal rotation of 19.31° ± 5.71° and 10.17° ± 3.84°, respectively. The increase in maxillary intermolar distance, evaluated at the mesiobuccal cusps, was 2.63 ± 1.56 mm. The miniscrew-anchored cantilever was effective for maxillary molar distalization. Sagittal, lateral, and vertical movements were observed for all maxillary teeth. Distal movement was progressively greater from anterior to posterior teeth.

Effect of attachment type on distal bodily movement of the maxillary canine in aligner orthodontics: a finite element study.

To clarify the effect of attachment types on bodily movement of the maxillary canine in aligner orthodontics. Using an aligner, the canine was moved bodily by 0.1 mm distally as a target position. Orthodontic tooth movement was simulated using the finite element method (FEM). The alveolar socket was displaced in the same manner as the initial movement caused by elastic deformation of the periodontal ligament. First, the initial movement was calculated, and then the alveolar socket was displaced in the same direction and with the same magnitude as the initial movement. These calculations were repeated to move the teeth after placement of the aligner. The teeth and the alveolar bone were assumed to be rigid bodies. A FEM model of the aligner was made based on the crown surfaces. The thickness of the aligner was 0.45 mm, and its Young's modulus was 2 GPa. Three types of attachments-semicircular couple, vertical rectangular, and horizontal rectangular-were placed on the canine crown. Regardless of the type of attachment, upon placement of the aligner on the dentition the crown of the canine moved to the target position, while the apex hardly moved. That is, the canine tipped and rotated. After repeating the calculation, the canine became upright and moved bodily regardless of the attachment type. In the aligner without an attachment, the canine did not become upright. There was almost no difference among attachment types in terms of achieving bodily movement of the canine.