• The korean journal of orthodontics
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• v.51 no.1
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• pp.32-42
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• 2021

Objective: To investigate the three-dimensional forces created by clear aligners on mandibular teeth during differential activation with en-masse retraction and/or intrusion in vitro. Methods: Six sets of clear aligners were designed for differential en-masse retraction and/or intrusion procedures in a first premolar extraction model. Group A0 was a control group with no activation. Groups A1-5 underwent different degrees of retractions and/or intrusions. Each group consisted of 10 aligners. Aligner forces were measured on a multi-axis force/torque transducer measurement system in real-time. Results: In the en-masse retraction groups (A1 and A2), lingual and extrusive forces were observed on the incisors; the canines mainly received distal forces; intrusive forces were seen on the second premolars; and the molars received mesial forces. In the en-masse retraction and intrusion groups (A3, A4, and A5), incisors also received lingual and extrusive forces; canines received distal and intrusive forces; mesial and extrusive forces were seen on the second premolars; and the second molars received distal and intrusive forces. The vertical forces on the incisors did not differ significantly among groups A1, A3, and A5. However, the vertical forces on the second premolars reversed from intrusion in group A1 to extrusion in groups A3 and A5. Conclusions: With clear aligners, the "bowing effect" is seen during en-masse anterior teeth retraction and can be partially relieved by performing en-masse retraction accompanied by anterior teeth intrusion. Vertical control of incisors remained unsolved during en-masse retraction, even when intrusive activation was added to the anterior teeth.

• The korean journal of orthodontics
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• v.22 no.1
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• pp.241-251
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• 1992

The purpose of this study was to investigate the root resorption pattern in incisors in dog under intrusive orthodontic loadings of various magnitude and duration. Intrusive forces were generated by closed coil springs. Force magnitudes were 15-30gm, 50-60gm and 80-110gm. Durations were continuous and intermittent. Intermittent duration was applied at intervals of 12 hours. The readjustment of the force was done every 4 days. The forces were maintained for 30 days. All specimens were decalfied, embedded in paraffin and stained with hematoxylin-eosin stain. Observations were made with light microscope. The following results were obtained; 1. The continuity of root surface was ceased in all, except intermittent forced teeth with 25gm. 2. The root resorptions, cementoclasts and cemental lacunae, were increased around periapical regions and the destructive scope of bone was deeply extended as the exerted orthodontic forces increased. 3. It was inspected that, under the same forces, root resorption and bone destruction were more deeply appeared in the continuously forced teeth than the intermittently forced ones. 4. All of the alveolar bone, showed direct and undermining bone resorptions.

• The korean journal of orthodontics
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• v.41 no.6
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• pp.384-398
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• 2011

Objective: The purpose of this study was to analyze the stress distribution and the displacement pattern of mandibular anterior teeth under various intrusive force vectors according to the position of orthodontic miniscrews and hooks, using three-dimensional finite element analysis. Methods: A three-dimensional finite element model was constructed to simulate mandibular teeth, periodontal ligament, and alveolar bone. The displacement of individual tooth on three-dimensional planes and the von Mises stress distribution were compared when various intrusion force vectors were applied. Results: Intrusive forces applied to 4 mandibular anterior teeth largely resulted in remarkable labial tipping of the segment according to the miniscrew position. All 6 mandibular anterior teeth were labially tipped and the stress concentrated on the labiogingival area by intrusive force from miniscrews placed mesial to the canine. The distointrusive force vector led to pure intrusion and the stress was evenly distributed in the whole periodontal ligament when the hook was placed between the central and lateral incisors and the miniscrew was placed distal to the canine. Conclusions: Within the limits of this study, it can be concluded that predictable pure intrusion of the 6 anterior teeth segment may be accomplished using miniscrews placed distal to the canine and hooks located between the central and lateral incisors.

• The korean journal of orthodontics
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• v.23 no.4 s.43
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• pp.485-492
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• 1993

Multiloop Edgewise Archwire(MEAW) is effective in relief the Curve of Spee in mandibular arch but up Sl down orthodontic elastics must be used with it. The purpose of this study was to analyse the effect of orthodontic elastics, like as up & down elastics, Class II elastics, and Class III elastics, and the effect of L loop in Multioop Edgewise Archwire. 1. Intrusive force of MEAW in anterior teeth was reduced and uprighting force in premolars was increased by up & down elastics. 2. Uprighting force was significintly increased with Class III elastics in multiple L loop arch wire. 3. The force of Class II elastics made molars tip mesially and Curve of Spee deep.

• The korean journal of orthodontics
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• v.18 no.2
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• pp.387-404
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• 1988

The purpose of this study was to investigate the root resorption and repair pattern of human teeth under intrusive orthodontic loadings of varying magnitude and duration. 50 gms, 100 gms, 200 gms of force applied to the 96 experimental teeth with duration of 2, 5, 7, 10 weeks, after removing the arch wire and retaining during 2 and 6 weeks, experimental teeth were extracted. Results were as follows: 1. The initial resorption site was visible in the apex within 2 weeks with 50 gms, 100 gms samples. 2. The sites of resorption increased markedly with duration of the force. 3. The 50 grams samples of the all duration reveal the shallow resorption and the 100 gms samples of the all duration except 2 weeks reveal the shallow and deep resorption sites. 4. After 7 weeks with 50 gms and 100 gms, cellular cementum repair accompanied the continuing resorption. 5. 2 and 6 weeks after removing the force with 200 gms, the same cellular cementum repair accompanied with 50 gms, 100 gms samples.

• The korean journal of orthodontics
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• v.29 no.5 s.76
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• pp.535-549
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• 1999

The Purposes of this study were to investigate the initial tissue changes on the teeth and surrounding tissues under contraction and intrusive force by contraction UTA. A control and experimental dogs, 10-months in age, were studied. Contraction and intrusive force(60gm) were applied at upper four incisors by contraction UTA. Experimental dogs were sacrificed at 2 weeks and 4 weeks after force application, respectively. In this study, 2 experimental groups were designed by the duration of force applied(E1, E2). The specimens were taken around the upper first and second incisor in each groups and were prepared for the H-E and MT stain for light microscopic observation. From the results of the study, the following conclusions may be drown. : 1. In control group, the periodontal ligament width was constant from apical third to cervical third of the root and periodontal fiber arrangement was horizontal or oblique in cervical third, oblique in middle third and apical third. In alveolar bond, smooth appearance was shown with osteoblast. 2. In experimental group 1, in proportion to force was concentrated at labial middle third and apical third of root of the upper first and second incisors, root of these tooth tipped labially and intruded at a time. 3. In experimental group 2, periodontal ligament width and arrangement was similar to control and observed strong calcified response at the labial middle third of root. But, alveolar bond resorption and cementum resorption were as before seen at labial middle third and apical third of root that force was concentrated.

• Journal of the korean academy of Pediatric Dentistry
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• v.27 no.3
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• pp.431-437
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• 2000

Traumatic intrusive luxation, an occurrence common in the primary dentition but one that occurs rarely in the permanent dentition, has a poor prognosis. There have been many treatment approaches such as allowing the tooth to reerupt spontaneously, surgical repositioning and immediate luxation, surgical luxation, and orthodontic repositioning; but all have their own drawbacks. Meanwhile, Turley et al. (1987) have proposed surgical and orthodontic combination therapy to treat intrusion. Surgical and orthodontic combination therapy means to apply the orthodontic traction force immediately after surgical luxation. If ankylosis occurs, orthodontic force may be applied after re-luxation repeatedly. But in cases of complete intrusive luxation, it would be not feasible to bond an orthodontic button or bracket on the tooth directly. Thus, in this case, traction of the tooth was attempted after surgically repositioning it close to the probable original socket site to promote better healing.

• The korean journal of orthodontics
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• v.18 no.2
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• pp.475-488
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• 1988

Certain malocclusion are associated with specific "facial type," and it is important for the clinician to classify the common facial characteristic of each patient. Because the reaction to treatment mechanics and the stability of the denture is depended upon the analysis of the facial pattern. Basically, there are 3 district facial types or patterns under which almost all malocclusion can be classified. 1. mesofacial is the most average growth. 2. brachyfacial which is a horizontal growth pattern has a week muscle, with dental arch, deep bite. 3. dolichofacial which is a vertical growth pattern has a strong muscle, narrow dental arch, open bite. Brachyfacial pattern show a resistant to mandibular rotation during treatment can accept a more protrusive denture and are prominantly nonextraction, whereas dolichofacial patterns tend to open during treatment require a more retracted denture in order to assure post-treatment stability. Brachyfacial pattern would better treat to use extrusive force system, whereas dolichofacial pattern treat to use intrusive force system with head gear and intermaxillary elastics.

• The korean journal of orthodontics
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• v.45 no.1
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• pp.20-28
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• 2015

Objective: The purpose of this study was to observe stress distribution and displacement patterns of the entire maxillary arch with regard to distalizing force vectors applied from interdental miniscrews. Methods: A standard three-dimensional finite element model was constructed to simulate the maxillary teeth, periodontal ligament, and alveolar process. The displacement of each tooth was calculated on x, y, and z axes, and the von Mises stress distribution was visualized using color-coded scales. Results: A single distalizing force at the archwire level induced lingual inclination of the anterior segment, and slight intrusive distal tipping of the posterior segment. In contrast, force at the high level of the retraction hook resulted in lingual root movement of the anterior segment, and extrusive distal translation of the posterior segment. As the force application point was located posteriorly along the archwire, the likelihood of extrusive lingual inclination of the anterior segment increased, and the vertical component of the force led to intrusion and buccal tipping of the posterior segment. Rotation of the occlusal plane was dependent on the relationship between the line of force and the possible center of resistance of the entire arch. Conclusions: Displacement of the entire arch may be dictated by a direct relationship between the center of resistance of the whole arch and the line of action generated between the miniscrews and force application points at the archwire, which makes the total arch movement highly predictable.

• The korean journal of orthodontics
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• v.27 no.3 s.62
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• pp.401-409
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• 1997

The purpose of this study was to analize the initial stress distribution around apex and the alveolar bone of the upper anterior teeth when applying intrusive force by the use of utility arthwire, Burstono 3-piece infusion archwire, and 'J' hook headgear which is usually used in clinital practice. By the use of the polarization plate, initial stresses were analized when 80g and 150g forte applied. The results were as follows. 1. With the utility archwire, moderate levels of stress were evenly distributed on the apical areas of the anterior teeth and concentrated on the apical areas of the first molars. 2. With the Burstone's 3-piece intrusion archwire, moderate levels of stress were evenly distributed on the apical areas of the anterior and posterior teeth. 3. With the 'J' hook headgear, severe levels oi stress were widely distributed on the alveolar bone and apical areas of the upper anterior teeth, and concentrated on the apical area between the central and the lateral incisors. Especially, weak levels of stress appeared along the periodontal ligament space of all teeth.