OBJECTIVE: The purposes of this study were to evaluate the force and stress depending on the type, deflection and thickness of the materials and to evaluate the mechanical properties of thermoplastic materials after repeated loading. METHODS: Four types of thermoplastic products were tested. Force until the deflections of 2.0 mm and the stress when the materials were restoring to its resting position were evaluated. The mechanical properties of thermoplastic materials evaluated after 5 repeated loading cycles. RESULTS: The interaction was observed between the thickness and the deflection (p < 0.05) from the regression equation. Thickness and amount of deflection rather than products and materials showed the largest effect on force and stress. In all products, at least 159 gf of force was required for more than 1.0 mm deflection or when materials with 1.0 mm thickness were deflected. The stress recorded was more than 19 gf/mm2. During repeated loading, each group showed significant difference on the force and the stress p < 0.01), 10 - 17% reduction of force and 4 - 7% reduction of stress in average. CONCLUSIONS: Proper thickness of thermoplastic materials and deflection level of tooth movement should be decided for the physiologic tooth movement. Force decay after repeated loading should be considered for the efficient tooth movement.
Tooth Movement

Recently, magnetic forces are considered as a method for more efficient tooth movement. The purpose of this study was to evaluate the effects of the changes of the magnetic volume on the magnetic forces. The universal testing machine and the electronic balance were used for the exact measurement of the force with constant air gap. While the magnet was kept same on one side, the magnetic volume of the other side was increased gradually in four manners. In the first group, the thickness was increased by adding same size of the magnets one after another while the thickness was increased by changing with a thicker magnet gradually in the second group. In the third group, the width was increased by adding same size of the magnets while the width was increased by changing with a wider magnet gradually in the last group. The results were as follows: 1. With the increase of the thickness, the magnetic force increased, while the magnetic force decreased with the increase of the width. 2. The magnetic force according to the change of the magnetic volume showed the distribution of the logarithmic function. 3. An originally thick magnet showed larger force tharr the added magnets although both of them had same volume.
Tooth Movement

The aim of this investigation was to evaluate the differences of two canti-lever springs by using a new simulation system. This was done using a Calorific machine that compared crown uprighting spring and root uprighting spring. The Calorific machine was designed to allow observation of the whole process of tooth moving, and it composed of three parts(a temperature regulation system, electro-thermodynamic teeth, and an artificial alveolar bone component). The obtained results wee as follows. 1. Distal and buccal movement of the anchor teeth were observed greater in the root uprighting spring than the crown uprighting spring. 2. Crown uprighting spring showed distal movement of the crown of lower second molar for 3.29mm but root uprighting spring showed only 1.68mm. 3. Crown uprighting spring exhibited forward movement of mesial and distal root of the lower second molar for 3.91mm, 3.60mm but the root uprighting spring showed 6.76mm, 6.26 mm.
Crowns ; Molar* ; Tooth Movement* ; Tooth*

This study was performed, by Finite Element Method, to evaluate the stress distribution on the periodontal tissue according to activation of the various closing loops and to predict the pattern of movement of maxillary incisors. At the same time, bull loop, key-hole loop, T-loop, combination loop and asymmetrical T-loop which were used for retraction of maxillary incisors was analysed by Finite Element Method. The following results were obtained. 1. Horizontal force wits the greatest in bull loop, the followed by key-hole loop, combination loop, T-loop and initial tooth movement exhibited uncontrolled tipping. 2. Horizontal force in asymmetrical T-loop compared to other closing loops was remarkably decreased, and the intrusive force on the incisors occurred. 3. As torque was increased, the moment was increased as a linear increment. 4. As moment was increased, initial movement of tooth changed to root movement from uncontrolled tipping.
Incisor* ; Tooth ; Tooth Movement ; Torque

A treatment should be functional, esthetic, conservative and periodontally healthy in order to meet criteria of an ideal dental procedure. in a prsthodontic patient with horizontal and/or vertical space deficiency, orthodontic tooth movement should be considered as a pre-prosthetic procedure. With a conventional technique, orthodontic treatment is a time-consuming and uncomfortable procedure. Pre-prosthetic orthodontic treatment, however, is no longer difficult procedure with the help of recently developed techniques, such as passive bracketing. The present article outlines the problems and causes of horizontal and vertical space deficiency in prosthodontic patients, and presents efficient pre-prosthetic orthodontic treatment modalities with typical clinical cases.
Humans ; Prosthodontics* ; Tooth Movement

OBJECTIVE: This study compared occlusal contact areas of ideally planned set-up and accomplished final models against the initial in class I and II molar relationships at finishing. METHODS: Evaluations were performed for 41 post-orthodontic treatment cases, of which 22 were clinically diagnosed as class I and the remainder were diagnosed as full cusp class II. Class I cases had four first premolars extracted, while class II cases had maxillary first premolars extracted. Occlusal contact areas were measured using a three-dimensional scanner and RapidForm 2004. Independent t-tests were used to validate comparison values between class I and II finishings. Repeated measures analysis of variance was used to compare initial, set up, and final models. RESULTS: Molars from cases in the class I finishing for the set-up model showed significantly greater contact areas than those from class II finishing (p < 0.05). The final model class I finishing showed significantly larger contact areas for the second molars (p < 0.05). The first molars of the class I finishing for the final model showed a tendency to have larger contact areas than those of class II finishing, although the difference was not statistically significant (p = 0.078). CONCLUSIONS: In set-up models, posterior occlusal contact was better in class I than in class II finishing. In final models, class I finishing tended to have larger occlusal contact areas than class II finishing.
Bicuspid ; Molar* ; Tooth Movement

Orthodontic treatment is a time-consuming process whose duration usually takes 2-3 years. In general, long-term treatment duration possesses higher risks of complications, which may have adverse impact on patients. Therefore, exploring safe and effective adjunctive interventions to accelerate orthodontic tooth movement and shortening the treatment duration are of profound clinical significance. Currently, numerous adjunctive interventions have been generated and developed to accelerate orthodontic tooth movement, which can be divided into two main categories: surgical and non-surgical. However, an intervention that is widely accepted as a routine practice in orthodontic clinic is lacking. This article aims to review com-mon adjunctive interventions used to accelerate orthodontic tooth movement. This review can be used as a basis to guide clinical practice, shorten treatment duration, and improve patients' prognosis.
Humans ; Tooth Movement Techniques

In maxillary canine retraction by means of sliding mechanics, we designed MAS(molar anchoring spring) to prevent anchorage loss and uncontrolled tipping of tooth movement and have applied it in clinical cases. The anchorage control of the maxillary first molar and type of tooth movement of the maxillary canine were studied in 31 subjects. The measurements were made on cephalograms, orthopantomograms and dental casts. The obtained results were as follows. 1. In case of the maxillary first molar, there was a little sagittal anchorage loss, but there was no vertical & transverse anchorage loss. 2. In case of the maxillary canine, there was distal tipping movement and also there was a little intrusion tendency.
Mechanics ; Molar* ; Tooth Movement

Self-ligating brackets have a permanently installed movable component to entrap the archwire which reduces much of the friction created by conventional ligation. Therefore, it allows for rapid tooth movement and shorter overall treatment time. Due to these advantages, interest in self-ligating brackets is increasing. In this report, several practical considerations for using self-ligating brackets are given to appreciate and maximize their benefits. It is thought that self-ligating brackets make shorter and more efficient treatment possible.
Friction ; Ligation ; Tooth Movement

OBJECTIVE: This study was performed to investigate an appropriate degree of prestretch for orthodontic synthetic elastomeric chains focusing on time-dependent viscoelastic properties. METHODS: Orthodontic synthetic elastomeric chains of two brands were prestretched to 50, 100, 150, and 200% of the original length in one and three cycles, and the hysteresis areas of the obtained stress-strain curves were determined. Acrylic plates were employed to maintain constant strain during the experiment. A total of 180 samples were classified into nine groups according to brand, and their stresses and permanent deformations were measured immediately after prestretch (0 hour), after 1 hour and 24 hours, and after 1, 2, 3, 4, 5, 6, 7, and 8 weeks. The relationship between stress relaxation and permanent deformation was investigated for various degrees of prestretch, and the estimated stress resulting from tooth movement was calculated. RESULTS: The degree of prestretch and the stress relaxation ratio exhibited a strong negative correlation, whereas no correlation was found between the degree of prestretch and the average normalized permanent strain. The maximal estimated stress was observed when prestretch was performed in three cycles to 200% of the original length. CONCLUSIONS: Although prestretch benefited residual stress, it did not exhibit negative effects such as permanent deformation. The maximal estimated stress was observed at the maximal prestretch, but the difference between prestretch and control groups decreased with time. In general, higher residual stresses were observed for product B than for product A, but this difference was not clinically significant.
Elastomers* ; Relaxation* ; Tooth Movement