• The korean journal of orthodontics
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• v.39 no.2
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• pp.83-94
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• 2009

Objective: The aim of this study was to investigate the 3-dimensional position of the center of resistance of the 4 maxillary anterior teeth, 6 maxillary anterior teeth, and the full maxillary dentition using 3-dimensional finite element analysis. Methods: Finite element models included the whole upper dentition, periodontal ligament, and alveolar bone. The crowns of the teeth in each group were fixed with buccal and lingual arch wires and lingual splint wires to minimize individual tooth movement and to evenly disperse the forces to the teeth. A force of 100 g or 200 g was applied to the wire beam extended from the incisal edge of the upper central incisor, and displacement of teeth was evaluated. The center of resistance was defined as the point where the applied force induced parallel movement. Results: The results of study showed that the center of resistance of the 4 maxillary anterior teeth group, the 6 maxillary anterior teeth group, and the full maxillary dentition group were at 13.5 mm apical and 12.0 mm posterior, 13.5 mm apical and 14.0 mm posterior, and 11.0 mm apical and 26.5 mm posterior to the incisal edge of the upper central incisor, respectively. Conclusions: It is thought that the results from this finite element models will improve the efficiency of orthodontic treatment.

• The korean journal of orthodontics
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• v.39 no.5
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• pp.278-288
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• 2009

Objective: The aim of this study was to investigate the changes in the center of resistance of the maxillary teeth in relation to alveolar bone loss. Methods: A finite element model, which included the upper dentition and periodontal ligament, was designed according to the amount of bone loss (0 mm, 2 mm, 4 mm). The teeth in each group were fixed with buccal and lingual arch wires and splint wires. Retraction and intrusion forces of 200 g for 4 and 6 anterior teeth groups and 400 g for the full dentition group were applied. Results: The centers of resistance were at 13.5 mm, 14.5 mm, 15 mm apical and 12 mm, 12 mm, 12.5 mm posterior in the 4 incisor group; 13.5 mm, 14.5 mm, 15 mm apical and 14 mm, 14 mm, 14.5 mm posterior in the 6 anterior teeth group; and 11 mm, 13 mm, 14.5 mm apical and 26.5 mm, 27 mm, 25.5 mm posterior in the full dentition group respectively according to 0 mm, 2 mm, 4 mm bone loss. Conclusions: The center of resistance shifted apically and posteriorly as alveolar bone loss increased in 4 and 6 anterior teeth groups. However, in the full dentition group, the center of resistance shifted apically and anteriorly in the 4 mm bone loss model.

• The korean journal of orthodontics
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• v.44 no.5
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• pp.236-245
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• 2014

Objective: To evaluate the therapeutic effects of a preformed assembly of nickel-titanium (NiTi) and stainless steel (SS) archwires (preformed C-wire) combined with temporary skeletal anchorage devices (TSADs) as the sole source of anchorage and to compare these effects with those of a SS version of C-wire (conventional C-wire) for en-masse retraction. Methods: Thirty-one adult female patients with skeletal Class I or II dentoalveolar protrusion, mild-to-moderate anterior crowding (3.0-6.0 mm), and stable Class I posterior occlusion were divided into conventional (n = 15) and preformed (n = 16) C-wire groups. All subjects underwent first premolar extractions and en-masse retraction with preadjusted edgewise anterior brackets, the assigned C-wire, and maxillary C-tubes or C-implants; bonded mesh-tube appliances were used in the mandibular dentition. Differences in pretreatment and post-retraction measurements of skeletal, dental, and soft-tissue cephalometric variables were statistically analyzed. Results: Both groups showed full retraction of the maxillary anterior teeth by controlled tipping and space closure without altered posterior occlusion. However, the preformed C-wire group had a shorter retraction period (by 3.2 months). Furthermore, the maxillary molars in this group showed no significant mesialization, mesial tipping, or extrusion; some mesialization and mesial tipping occurred in the conventional C-wire group. Conclusions: Preformed C-wires combined with maxillary TSADs enable simultaneous leveling and space closure from the beginning of the treatment without maxillary posterior bonding. This allows for faster treatment of dentoalveolar protrusion without unwanted side effects, when compared with conventional C-wire, evidencing its clinical expediency.

• The Journal of Korean Academy of Prosthodontics
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• v.28 no.2
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• pp.91-108
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• 1990

The purpose of this study was to compare the maganitude of the discrepancies of the mounting errors in according to the states of dentitions, and to the superoinferior, anteroposterior, and rightleft driecetions. GROUP I. : Fourteen patients 22 to 26 years of age with a full complement of teeth, were used in the study. The criteria fro patient selection were a complete dentition, sparse restorarive treatment, and adequate posterior and anterior occlusan stops. And they had no sign and sympton at TMG area. GROUPII. : Eigth patients 37 to 62 years of age with bilateral free ends. The criteria for patient selection were Kennedy classification class 1 cases, and adequate posterior and anterior stops. And the opposite dentitions were a full complement of teeth. Irreversible hydrocolloid impresiion of each arch was taken of each patient. These were immediatel poured in stone and mounted on a Denar Mark II. Articulator with the arbitrary slidematic face-bow. With hand articulation th e mandibular cast was mounted to the maxillary cast in centric occlusion. Five types of interocclusal records were taken of each patient : (1) aluwax (2) baseplate wax; (3) znic oxide-eugenol pasts; (4) polyether (Ramitec); (5) modeling compound. All measurement of the five selected recording materials were compared with those of the hand-articulated full arch models in centric occlusion or maximum interdigitation. The results were as follows; 1. There were statistical differences in amount of devitation in according to the materials and the states of dentition. The amount of deviation of compound was the largest. 2. There were statistical differences in amount of deviation in complete dentition at all directions. The amount of diviation of compound was the largest. And at the right-left direction the amount of znic oxide-eugenol paste was larger than that of baseplate wax. 3. There was a statistical difference in amount of diviations in partial edentulous dentition at the superoinferior direction. The amount of deviation of compound was larger than that of znic oxide-eugenol paste. 4. There was as statistical difference in amount of deviations in partial edentulous dentition at the right-left direction. The amount of deviation of baseplate wax was larger that tnat of polyether. 5. There was not a statistical difference in amount of diviation in partial edentulous dentition at the anteroposterior direction.