Vertical Tooth Movement Research Articles

Comparison between 2D cephalometric and 3D digital model superimpositions in patients with lateral incisor agenesis treated by canine substitution

This study aimed to assess the reliability of measurements obtained after superimposing 3-dimensional (3D) digital models by comparing them with those obtained from lateral cephalometric radiographs in patients with lateral agenesis space closure by mesialization. Data were collected from premaxillary and postmaxillary dental casts and lateral cephalometric radiographs of 26 patients presenting lateral incisor agenesis and treated with rapid maxillary expanders and space closure by mesialization of the lateral sectors. Sagittal and vertical movements of the incisors and the maxillary molars were evaluated with lateral cephalometric radiographs and digitized 3D models superimposed on the palatal area. Paired sample ttests were used to determine if any significant difference existed between the 2 measuring techniques and between 2 different localizations of superimpositions. Cephalograms and 3D digital model measurements were statistically similar in molars and incisor movements according to anteroposterior and vertical planes. Regarding incisor movements in the anteroposterior plane, measurements derived from second ruga 3D models were significantly greater than those derived from third ruga 3D digital models. The 3D model superimposition method using the palate as a reference area is clinically reliable for assessing anteroposterior and vertical tooth movement as cephalometric superimposition in patients treated with rapid maxillary expanders and space closure by mesialization.

Natural reference structures for three-dimensional maxillary regional superimposition in growing patients

BackgroundAssessment of growth-related or treatment-related changes in the maxilla requires a reliable method of superimposition. Such methods are well established for two-dimensional (2D) cephalometric images but not yet for three-dimensions (3D). The aims of this study were to identify natural reference structures (NRS) for the maxilla in growing patients in 3D, opportunistically using orthodontic mini-screws as reference; and to test the applicability of the proposed NRS for maxillary superimposition by assessing the concordance of this approach with Björk’s ‘stable reference structures’ in lateral projection.MethodsThe stability of the mini-screws was tested on longitudinal pairs of pre- and post-orthodontic cone-beam computed tomography (CBCT) images by measuring the distance changes between screws. After verifying the stability of the mini-screws, rigid registration was performed for aligning the stable mini-screws. Then, non-rigid registration was used to establish the dense voxel-correspondence among CBCT images and calculate the displacement of each voxel belonging to the maxilla relative to the mini-screws. The displacement vectors were transformed to a standardized maxillary template to categorize the stability of the internal structures statistically. Those voxels that displaced less relative to the mini-screws were considered as the natural reference structures (NRS) for the maxilla. Test samples included another dataset of longitudinal CBCT scans. They were used to evaluate the applicability of the proposed NRS for maxillary superimposition. We assessed whether aligning the maxilla with proposed NRS is in concordance with the maxillary internal reference structures superimposition in the traditional 2D lateral view as suggested by Björk. This was quantitively assessed by comparing the mean sagittal and vertical tooth movements for both superimposition methods.ResultsThe stability of the mini-screws was tested on 10 pairs of pre- and post-orthodontic cone-beam computed tomography (CBCT) images (T1: 12.9 ± 0.8 yrs, T2: 14.8 ± 0.7 yrs). Both the loaded and the unloaded mini-screws were shown to be stable during orthodontic treatment, which indicates that they can be used as reference points. By analyzing the deformation map of the maxilla, we confirmed that the infraorbital rims, maxilla around the piriform foramen, the infrazygomatic crest and the hard palate (palatal vault more than 1 cm distal to incisor foramen except the palatal suture) were stable during growth. Another dataset of longitudinal CBCT scans (T1: 12.2 ± 0.63 yrs, T2: 15.2 ± 0.96 yrs) was used to assess the concordance of this approach with Björk’s ‘stable reference structures’. The movement of the maxillary first molar and central incisor showed no statistically significant difference when superimposing the test images with the proposed NRS or with the classic Björk maxillary superimposition in the lateral view.ConclusionsThe infraorbital rims, maxilla around the piriform foramen, the infrazygomatic crest and the hard palate (palatal vault more than 1 cm posterior to incisal foramen except the palatal suture) were identified as stable regions in the maxilla. These stable structures can be used for maxillary superimposition in 3D and generate comparable results to Björk superimposition in the lateral view.

Measurement of tooth displacement

The periodontium is a biological structure that supports the tooth in the jaw and behave as a developmental, biological, and functional unit. Teeth may be considered to be ‘suspended’ in their tooth sockets which provides teeth the ability to move in response to an applied load. In terms of the protection the suspension effect of the periodontal ligament may offer dental restorations, movement in an axial direction is of interest. No device or system to measure this movement is readily available, thus a novel approach had to be developed to address the questions of this research. The device developed allowed images to be taken of the participants teeth before, during and after a participant bit down on the tooth and used to measure the displacement of the tooth in image processing software. Average maximum tooth displacement from all participants of 73.8 μm (sd = 22.5 μm) were recorded. Longer application time of bite force was associated with greater cumulative tooth displacement, for a given level of force, and female participants experienced approximately 2 μm more displacement per Newton than males. The device and methods utilised in this study has shown good potential as a measurement protocol for measurement of vertical tooth movements in vivo. The response to load the teeth in this study has shown, highlighted the visco-elastic properties of the periodontal ligament and the amount of movement recorded supports the protection that controlled tooth movement offers teeth.

Posterior Dahl: A Minimally Invasive Method for the Treatment of Localized Posterior Tooth Wear.

This retrospective case series of 9 patients aimed to describe clinical outcomes and patient satisfaction following the implementation of the posterior Dahl concept to manage localized posterior tooth wear. Localized occlusal space was created in the posterior dentition. Supra-occluding direct restorations were placed bilaterally for the restoration of molars. Intraoral scans were taken at the pre-treatment stage, immediately post-restoration, and during follow-up appointments. Scans were used to undertake analysis of any occlusal changes and re-establishment of the occlusion. A questionnaire was used to assess patient satisfaction, alleviation of any pre-treatment concerns, and evaluation of post-treatment complaints. Immediately post-treatment, all patients showed an increase in the vertical dimension. Opening of the bite in the untreated areas following restoration of worn posterior molars resulted either in a tendency towards or the actual reestablishment of the occlusion. One patient completely lacked compensatory vertical tooth movement in the untreated areas, culminating in the persistence of a vertical open bite. One restoration displayed cohesive fracture after 4 months. Pre-treatment problems (eg, sensitivity) were fully resolved amongst all patients after 6 months. Post-treatment complaints were minor and demonstrated resolution within a relatively short period of time. Eight patients reported being "very satisfied" with their treatment outcomes. Application of the posterior Dahl concept appears to offer a promising, relatively simple, minimally invasive and effective approach for the management of localized posterior tooth wear, which is well accepted by patients.

Vertical control in fixed orthodontics- A review

Control of vertical dimension is recognised as an important as well as often difficult part of orthodontic treatment. Ineffective vertical control cause downward and backward rotation of mandible, prolonged treatment times, and compromised treatment results. Vertical control is often difficult, as most methods used to exert vertical control are highly patient-dependent. Controlling vertical dentoalveolar development is often difficult, because most orthodontic mechanotherapy tends to produce vertical movement of teeth. Vertical movement of teeth are least resisted therefore immediate effect is seen. Vertical control is difficult also because most methods depends on patient compliance. Keywords: Vertical control, Hyperdivergent.

Are clear aligners as effective as conventional fixed appliances?

Design Systematic reviewStudy population Orthodontic patients undergoing treatment with removable thermoplastic retainers compared with conventional fixed orthodontic appliances. The mean age of patients was between 15 and 33 years. Data sources Six electronic databases including: Scopus, Web-of-Science, PubMed, Cochrane, Clinical Trials and Grey Literature were searched in addition to a search of references in eligible studies with no restriction of language. Out of 559 studies, 55 were eligible. Only four articles were included; three non-randomised and one randomised controlled trial (RCT) involving 96-182 patients. The studies included were completed within 2005-2016.Study selection Clinical trials involving orthodontic patients undergoing treatment using thermoplastic removeable aligners, namely Invisalign, in comparison to conventional fixed orthodontic appliances of either self-ligating or tip-edge bracket systems were included.Data extraction and synthesis Two members of the research team independently selected articles which fulfilled the inclusion criteria and compared results prior to data collection. A third party examiner was available to resolve disagreements. The study quality was analysed for presence of bias; three non-randomised studies were evaluated and scored using the Methodological Index for Non-Randomised Studies (MINORS), one study was considered high methodological quality, two were considered moderate. The RCT was assessed using the Cochrane Collaboration Common Scheme for Bias and was deemed to be low risk of bias. Results The results suggest that Invisalign can provide successful alignment, however, it poses difficulties in achieving occlusal contacts, buccolingual inclination and vertical movement of teeth. One study found that Invisalign cases are more susceptible to relapse, which can be explained through the tipping mechanism compared to bodily movement, of conventional fixed appliances. Furthermore some studies show that although using aligners can result in overall shorter treatment time the final occlusion was not favourable. The outcome of the RCT, showed that aligners can be successful in treating class I malocclusions in extraction cases.Conclusions This systematic review found that the use of clear aligners made no significant difference to treatment time compared with conventional appliances. Additionally, removable aligners were effective in crowding cases but had limitations in achieving favourable outcomes in the anterior-posterior position and final occlusion, as well as being more likely to relapse post treatment.

Three-Dimensional Evaluation of Change in Maxillary Alveolar Arch after Expansion in Unilateral Cleft Lip and Palate Patients

Narrowing of the maxillary dental arch is a major cause of occlusal abnormalities in cleft lip and palate patients. Although the dental arch may be expanded in such cases, relapse will often occur during the subsequent retention period. In this study, the stability of expansion of the maxillary arch was investigated by examining 3-dimensional change in the maxillary arch during the treatment and post-retention periods. Three-dimensional measurements was performed on maxillary plaster models obtained from 8 unilateral cleft lip and palate patients (mean age, 12.5 years) who had undergone maxillary arch expansion using an edgewise appliance and quad helix (CLP group). The controls consisted of 8 unilateral cleft lip and alveolus patients (mean age, 12.9 years). Measurements were made during the pretreatment, post-treatment, and post-retention periods. In the CLP group, horizontal relapse was observed in the alveolar and dental arches between the second premolars, together with vertical relapse on the cleft side of the central incisor, lateral incisor, and canine. The sites where relapse occurred demonstrated decreased growth before orthodontic treatment. A correlation was observed between the extents of expansion and relapse. These findings suggest that excessive horizontal or vertical tooth movement in areas showing developmental failure should be avoided in order to increase stability after orthodontic treatment.

Cone-beam computed tomographic evaluation of changes in maxillary alveolar bone after orthodontic treatment

This study examined the relationship of vertical and horizontal changes in the alveolar bone crest with upper incisor movement after orthodontic treatment. Tooth movement was measured on lateral cephalograms. Vertical and horizontal changes in the median alveolar crest and distance from the cementoenamel junction and anterior nasal spine to the alveolar crest were measured with cone-beam computed tomography. The incisal edge moved distally, and the cervical point intruded significantly and moved distally. The median alveolar crest decreased by 3.80 ± 2.05 mm. The distance from the labial cementoenamel increased significantly, by 0.35 ± 0.38 mm. The vertical distance from the anterior nasal spine decreased significantly, and the alveolar crest moved distally. Vertical tooth movement was positively associated with change in the distance from the labial cementoenamel junction and inversely associated with vertical change in the distance from the anterior nasal spine on the labial and palatal sides. Lingual tooth movement was positively and negatively correlated with horizontal changes in the labial and palatal alveolar crest and vertical change in the palatal alveolar crest. The lingual movement of incisors was related to labial bone resorption. Greater lingual and extrusive movement of incisors led to a greater decrease in the alveolar bone crest.

Effect of Cast Modification on Linear Dimensional Change of Acrylic Tooth Position Following Maxillary Complete Denture Processing.

To investigate the effect of different cast modifications on the vertical and horizontal tooth position following maxillary complete denture processing. A total of 60 maxillary master casts were prepared and arranged in six groups (n = 10). Variation in modifications between study groups 1 through 6 were as follows: no modification, butterfly post palatal seal preparation only, butterfly post palatal seal preparation with 10 mm wide/4 mm deep box, butterfly post palatal seal preparation with 10 mm wide/4 mm deep box and four round holes, butterfly post palatal seal preparation with 20 mm wide/4 mm deep box, butterfly post dam preparation with 20 mm wide/4 mm deep box and four round holes, respectively. The boxes in the respective groups were prepared on the mid-heel area of the cast. The first group was included in the study as control. The initial master cast was indexed to standardize the measurement technique on all specimens before duplication. Maxillary denture tooth set-up was completed and indexed using laboratory putty to ensure a similar set-up on all specimens. Vertical and horizontal tooth positions were measured for the maxillary left central incisor, right and left first molars in waxed complete dentures, and following processing. The measurements were done using a digital vernier caliper with manufacturing accuracy of up to 0.01 mm. The study data were entered in a Microsoft Excel Spreadsheet. Statistical analysis was done using a paired Student t-test, ANOVA, and Tukey post hoc test set at 5% level of significance. The paired t-test (within groups) showed significant change in all linear tooth positions for groups 1 and 2. Groups 3 through 6 had significant change in vertical dimension only. One-way ANOVA indicated that no significant difference was seen in the vertical tooth movements between the groups; however, statistically significant reduction was seen in the horizontal tooth movements at the maxillary left central incisor, right and left first molars for groups 3 through 6 when compared to others without significant difference between them. Within the limitations of the study, it was concluded that the movement of the teeth horizontally could be reduced with master cast modification (box alone or box and round holes) whereas the vertical movement of the teeth was not affected by the cast modifications made across all groups.

One palatal implant for skeletal anchorage--frequency and range of indications.

ObjectiveAim of this investigation was to analyze the frequency and range of indications of orthodontic treatments using one palatal implant for skeletal anchorage, in a time frame of four years.Material and methodsA sample was comprised by viewing retrospectively the patient collective of a specialized university clinic who started orthodontic treatment in the time frame 01/09-12/12. Inclusion criterion was the first application of a superstructure within the investigated period after successful insertion of a palatal implant (Ortho-System®, Straumann, Basel, Switzerland). Frequency and range of indications of the conducted skeletally anchored tooth movement were determined by analyzing the individual patient documentation such as medical records, radiographs and casts.ResultsFrom a total of 1350 patients who started orthodontic treatment in this period met 56 (=4.2%) the inclusion criterion. In 85.7% of this sample was sagittal orthodontic tooth movement conducted, most frequently mesialization of ≥1 tooth (44.6%). Vertical tooth movement was in 57.1% of the sample performed, mostly extrusion of ≥1 tooth (34%). In 33.9% of the sample was ≥1 displaced tooth orthodontically relocated. One or two upper incisors were in 16.1% of the sample permanently replaced by the superstructure, all but one even after orthodontic treatment. In 66.1% of all cases were multi-functional anchorage challenges performed.Conclusion4.2 % of all treated patients within the investigated period required orthodontic treatment with skeletal anchorage (palatal implant), mainly for performing sagittal tooth movement (mesialization). The palatal implant was primarily used for multi-functional anchorage purposes, including skeletally anchored treatment in the mandible.

Processing-induced Tooth Displacement and Occlusal Changes in Complete Dentures An Overview

Objectives: The aim of this overview is to discuss about ?The various factors and variables involved in complete denture processing that can contribute to tooth displacement in complete dentures. ?The precautions to be taken to minimize it. Materials and methods: A PubMed search was conducted ending in June 2015 using search terms; artificial tooth movement, tooth displacement, complete dentures, processing. Literature search was completed by hand search accessing the references cited in all the selected publications. Results: The literature search yielded 114 papers in PubMed. Twenty five articles were selected and cross references of these articles were checked. All the English language publications which met the defined objectives were included for the overview. Conclusion: From the present overview, we can conclude that the defined processing procedures must be carefully followed by dental clinicians, technicians and students to avoid occlusal errors in complete dentures due to linear and vertical tooth movement. Each step in the processing procedure must be meticulously carried out and the suggested preventive measures can be followed to ensure predictable treatment outcome.

Tooth positioners and their effects on treatment outcome.

Malocclusion can also be corrected by means of clear removable appliances called as “tooth positioners” or “aligners”. A tooth positioner is used to control settling and to minimize or eliminate relapse of the teeth after an orthodontic treatment. In this article, a complete review of the objectives, course of treatment, fabrication, and the materials used for fabrication of tooth positioners along with their importance and disadvantages were discussed. Tooth positioners did improve the overall orthodontic treatment outcome as quantified by the ABO (American Board of orthodontics) objective scoring method. But once the initial occlusal contact was achieved, the vertical movement of teeth was found to be inhibited.

In vitro force delivery of nickel-titanium superelastic archwires in vertical displacement

OBJECTIVE: The purpose of this study was to evaluate the force delivered by different superlastic nickel-titanium wires during vertical displacement, in order to determine whether their stress release meets the criteria for constant and light forces that are usually accredited to these archwires. METHOD: Ten samples of 6 brands of 0.016-in archwires (Ormco, GAC, Morelli, TP, American Orthodontics e Rocky Mountain) were tested in a complete metal model using Dynalock brackets (3M Unitek™). In the canine position, there was a sliding bracket connected to a pole. This set was related to a load cell of 0.5 kg attached to a universal testing machine (Autograph AG-199kNG, Shimadzu). The crosshead speed was 0.5 mm/min and the maximum displacement was 1.0 mm. The model was submerged in temperature-controlled water. The results were analyzed by ANOVA (p < 0.05), using the software SAS System 8.02, Cry, NC, USA. RESULTS: The TP archwire had the lowest force throughout the test, although the final force was high (277.91 g). The Rocky Mountain archwire had the highest force release (455.41 g). CONCLUSION: The different brands of wires tested in this study failed in delivering low and constant forces as expected from superlastic nickel-titanium wires. The forces were extremely heavy for a vertical tooth movement.

Tooth and bone research using genetically modified mice

Teeth and bone are both hard tissues and composed of hydroxyapatite. Tooth development initiates with the invasination of oral epithelium, followed by aggregation of supporting ectomesenchymal cells. From mouse study, numbers of molecules have been discovered to relate tooth development. These discoveries have helped to clarify the responsible genes of human genetic disorders with abnormal tooth number and structure. During tooth development, teeth erupt into the outer environment, oral cavity. From this point, teeth are completely different from bone which is always covered by soft tissues. Tooth eruption is composed of two different processes, that is, eruption pathway formation and vertical tooth movement. In this review, mutant mice with abnormal tooth development and eruption are introduced, and molecular mechanism required for this process is discussed.

Vertical alveolar growth in subjects with infraoccluded mandibular deciduous molars

Our objective was to compare vertical alveolar growth in areas adjacent to infraoccluded deciduous molars with growth in areas of deciduous molars and normal occlusion for a period of at least 1 year by using digital subtraction radiography. This case-control study included 40 pairs of panoramic radiographs of growing patients with infraoccluded deciduous molars and 40 pairs of radiographs of patients without infraoccluded deciduous molars. One radiograph at baseline was obtained at diagnosis, and the other at least 1 year later. The subjects and the controls were matched according to chronologic age and time interval between the 2 radiographs. The 2 groups were compared with regard to vertical alveolar growth and vertical tooth movement. Measurements were assessed by using nonparametric tests (Mann-Whitney and Friedman) and a multiple comparison test. Significance was set at 5%. A statistically significant difference was observed between the groups with regard to vertical alveolar growth measured on the bone crest between the first permanent molars and second premolars. Vertical alveolar growth between the first permanent molar and the second premolar adjacent to the infraoccluded teeth was smaller than in areas adjacent to teeth with normal occlusion.

Efficiency of noncompliance simultaneous first and second upper molar distalization: a three-dimensional tooth movement analysis.

Objective of this prospective study was the three-dimensional (3D) analysis of tooth movements after the noncompliance simultaneous distalization of the first and second maxillary molars. Ten patients (five girls and five boys; mean age: 13.2 years) with bilateral Class II molar relationships were treated with a noncompliance, fixed intraoral appliance. Upper second molars had already erupted in all cases. Dental casts and lateral cephalometric radiographs were taken immediately before placement and after removal of the appliance. The casts were 3D digitized and superimposed on a predefined area in the palate. The resulting holograms, as well as the cephalometric radiographs, were digitized and analyzed by means of customized cephalometric software. The whole procedure was repeated after a two- to four-week interval to estimate the error of both methods. The cast assessment of 3D sagittal and vertical tooth movements was more reliable than the cephalometric record. The average maxillary first molar distal movement was 2.8 mm. Anchorage loss was expressed by a 1.9-mm proclination of the central incisors. A substantial variation among patients and among the right and left side in the same patient was observed. Noncompliance simultaneous distalization of the first and second maxillary molars can be an efficient treatment option for the correction of Class II molar relationship. However, anchorage loss and individual variation have to be seriously considered. Bilaterally symmetrical effectiveness should not be relied upon.

Microanchor mediated upper molar intrusion in deep posterior bite after long-term edentulousness for prosthetic reconstruction with dental implants

Long-term edentulousness can lead to elongation of antagonistic teeth, making prosthetic rehabilitation impossible. An interdisciplinary case is presented where elongated teeth were successfully intruded by micoranchor-mediated orthodontic movement. To the right mandible, implants had been inserted correspondingly to the alveolar process height. However, the patient waited over 1 year for prosthetic treatment. The antagonistic maxillary teeth had elongated considerably. On the left side, elongated upper molars occluded with previously crowned and in the meantime unprovided teeth 35 and 37. On the right side, two palatal, three vestibular microanchors of 8 mm length and 1.6 mm diameter were used, on the left side, two palatal and two vestibular microanchors to intrude the teeth 14 to 17 and 26. The screwheads were connected to individually model-casted splints for bodily intrusion of the molars. This case illustrates how vertical tooth movements can be ventured by the use of orthodontic microscrews before either conventional or implant-borne prosthetic rehabilitation.

Comprehensive gene expression analysis in human periodontal ligaments of the mandibular third molars performing vertical movement and the maxillary second premolars with occlusal contact

The periodontal ligament (PDL) is thought to be an important tissue in vertical movement during tooth eruption, but the precise molecular mechanism is not known. Thereto, comprehensive gene expression was analyzed in human PDL of mandibular third molars performing vertical movement and maxillary second premolars with occlusal contact. The expression profile of 9,243 genes in the PDL of one subject was compared between vertically moving third molars and second premolars with occlusal contact by DNA microarray. The expression of 27 genes showed more than a 10-fold difference between third molars and second premolars. The expression of CALB1 (encoding calbindin 1), CYP26A1 (encoding cytochrome P450, family 26, subfamily A, polypeptide 1), SPOCK3 (encoding testican-3), CCK (encoding cholecystokinin) and SCRG1 (encoding scrapie responsive protein 1) was more than 30-fold higher in PDLs of the third molars than the second premolars. CALB1 is reported to increase at the pressure side of PDL during experimental orthodontic tooth movement in rats. Interestingly, in this study, CALB1 expression showed the largest difference. In contrast, CRCT1 (encoding cysteine-rich C-terminal 1), SPRP3 (encoding small proline-rich protein 3), IL8 (encoding interleukin 8) and MMP12 (encoding matrix metalloproteinase 12) showed more than 100-fold higher expression in PDLs of the second premolars than the third molars. The present comprehensive gene expression in PDLs provides new insights into the molecular mechanism during the vertical tooth movement.

Analysis of tooth movement in extraction cases using three-dimensional reverse engineering technology

Despite inherent errors, cephalometric superimpositions are currently the most widely used means for assessing sagittal and vertical tooth movements. The purpose of this study was to compare three-dimensional (3D) digital model superimposition with cephalometric superimposition. The material was collected from initial and final maxillary casts and lateral cephalometric radiographs of 30 patients (6 males, 24 females, mean age 17.7 years) who underwent orthodontic treatment with extraction of permanent teeth. Each pair of cephalograms was traced and superimposed according to Ricketts' four-step method. 3D scanning of the maxillary dental casts was performed using INUS dental scanning solution(R), which consists of a 3D scanner, an autoscan system, and 3D reverse modelling software. The 3D superimposition was carried out using the surface-to-surface matching (best-fit method) function of the autoscan system. The antero-posterior movement of the maxillary first molar and central incisor was evaluated cephalometrically and on 3D digital models. To determine whether any difference existed between the two measuring techniques, paired t-tests and correlation analysis were undertaken. The results revealed no statistical differences between the mean incisor and molar movements as assessed cephalometrically or by 3D model superimposition. These findings suggest that the 3D digital orthodontic model superimposition technique used in this study is clinically as reliable as cephalometric superimposition for assessing orthodontic tooth movements.

A numerical simulation of tooth movement by wire bending

In orthodontic treatment, wires are bent and attached to teeth to move them via elastic recovery. To predict how a tooth will move, the initial force system produced from the wire is calculated. However, the initial force system changes as the tooth moves and may not be used to predict the final tooth position. The purpose of this study was to develop a comprehensive mechanical, 3-dimensional, numerical model for predicting tooth movement. Tooth movements produced by wire bending were simulated numerically. The teeth moved as a result of bone remodeling, which occurs in proportion to stress in the periodontal ligament. With an off-center bend, a tooth near the bending position was subjected to a large moment and tipped more noticeably than the other teeth. Also, a tooth far from the bending position moved slightly in the mesial or the distal direction. With the center V-bend, when the second molar was added as an anchor tooth, the tipping angle and the intrusion of the canine increased, and movement of the first molar was prevented. When a wire with an inverse curve of Spee was placed in the mandibular arch, the calculated tendency of vertical tooth movements was the same as the measured result. In these tooth movements, the initial force system changed as the teeth moved. Tooth movement was influenced by the size of the root surface area. Tooth movements produced by wire bending could be estimated. It was difficult to predict final tooth positions from the initial force system.