• The korean journal of orthodontics
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• v.23 no.2 s.41
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• pp.147-163
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• 1993

The purpose of this stuy was to evaluated the cytotoxicity of brackets which were recycled thermally or chemically. New brackets and used brackets which had been in mouth for at least 2years were used as samples and human gingival cell culture and agar overlay technique was used to evaluate the cytotoxicity. From the experiment the following results were obtained : 1. New brackets in the as received state showed mild cytotoxicity. 2. Thermally recycled brackets except the used bracket not electropolished showed moderate cytotoxicity and among them new brackets showed greater cytotoxicity than used ones. 3. Used brackets which were thermally recycled without electropolishing showed mild cytotoxicity. 4. Among thermally recycled brackets, electropolished brackets showed greater cytotoxicity than not electro-polished ones. 5. Chemically recycled brackets showed moderate cytotoxicity, and among them, new brackets appeared to be more cytotoxic than used ones.

• The korean journal of orthodontics
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• v.45 no.1
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• pp.13-19
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• 2015

Objective: This study aimed to compare the frictional force (FR) in self-ligating brackets among different bracket-archwire angles, bracket materials, and archwire types. Methods: Passive and active metal self-ligating brackets and active ceramic self-ligating brackets were included as experimental groups, while conventional twin metal brackets served as a control group. All brackets were maxillary premolar brackets with 0.022 inch [in] slots and a $-7^{\circ}$ torque. The orthodontic wires used included 0.018 round and $0.019{\times}0.025$ in rectangular stainless steel wires. The FR was measured at $0^{\circ}$, $5^{\circ}$, and $10^{\circ}$ angulations as the wire was drawn through the bracket slots after attaching brackets from each group to the universal testing machine. Static and kinetic FRs were also measured. Results: The passive self-ligating brackets generated a lower FR than all the other brackets. Static and kinetic FRs generally increased with an increase in the bracket-archwire angulation, and the rectangular wire caused significantly higher static and kinetic FRs than the round wire (p < 0.001). The metal passive self-ligating brackets exhibited the lowest static FR at the $0^{\circ}$ angulation and a lower increase in static and kinetic FRs with an increase in bracket-archwire angulation than the other brackets, while the conventional twin brackets showed a greater increase than all three experimental brackets. Conclusions: The passive self-ligating brackets showed the lowest FR in this study. Self-ligating brackets can generate varying FRs in vitro according to the wire size, surface characteristics, and bracket-archwire angulation.

• The Journal of the Korean dental association
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• v.50 no.7
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• pp.394-406
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• 2012

Objective: The adhesion capabilities of different types of self-ligating brackets were measured with respect to Streptococcus mutans and Streptococcus sobrinus. Methods: Five types of self-ligating brackets (Clippy-C; Mini Clippy; Clarity-SL; Speed; Damon 3) were used for the experiment group and composite resin brackets (Spirit-MB), metal brackets (Victory) and polycrystalline alumina brackets (Clarity) were used for the control group. In order to assess adhesion of bacteria to the brackets, the brackets were cultured for 3, 6 and 24 hours in media containing bacteria and 20% sucrose. Results: There was no statistic difference in adhesion amount of Streptococcus mutans and Streptococcus sobrinus according to the types of brackets. A total adhesion amount according to bracket type was different. An extended incubation time increased adhesion amount. Observation under scanning electron microscope showed that Streptococcus sobrinus adhered more to Clippy-C and Victory rather than to Clarity-SL. Conclusions: Clarity-SL, a self-ligating esthetic bracket was confirmed to show lower bacterial adhesion to cariogenic bacteria, Streptococcus mutans and Streptococcus sobrinus group than other self-ligating brackets or conventional brackets, which suggests that proper use of self-ligating esthetic brackets might even be better in preventing tooth surface decalcification.

• The korean journal of orthodontics
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• v.15 no.2
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• pp.261-269
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• 1985

The purpose of this study was to measure and compare tensile strength for 3 types of new direct-bond brackets and the same brackets after recycling and to evaluate recycled brackets to determine the extent of physical alteration after recycling. Three types of new direct-bond brackets were bonded to recently extracted human premolar teeth and the tensile strength was measured by Universal Testing Machine. The brackets were recycled by thermal process and the tensile test was repeated. To determine the extent of physical alteration after recycling, the slot width and the hardness of metal brackets were measured and to analyze the microstructure of the brackets, photographs of the bracket microstructure were taken. Following results were obtained: 1. The tensile strength of recycled brackets was lower than that of new brackets, but there was no statistically significant difference. (p>0.05) 2. In the new and recycled brackets, the tensile strength of mini-mesh base bracket was statistically higher than that of conturlok base bracket, $(p\leq0.05)$ but there was no statistically significant difference between production of other companies. (p>0.05) 3. The slot width of metal bracket was enlarged from 0.459mm to 0.469mm as a result of the recycling process. (p>0.005) 4. As temperature was increased in thermal treatment, the grains of bracket metal gradually became coarser and the hardness was decreased.

• Journal of the Society of Naval Architects of Korea
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• v.43 no.2 s.146
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• pp.197-205
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• 2006

In general, brackets found at tank boundary are design according to the Classification Society Rule. Since much man power is needed in manufacturing the brackets stiffened by flange, it is necessary to suggest alternative designs, of which flanges are removed, through the rigorous structural analysis. In this paper non-linear structural analysis for brackets with and/or without flange have been carried out to examine their structural behavior and ultimate strengths. Alternative designs for brackets are suggested based on the results of ultimate strength analysis so that the alternative brackets have the similar level of strength and stiffness to the original brackets. It has been seen that the structural safety of alternative brackets proposed in this paper are beyond the appropriate level. The primary benefit of replacing the original brackets by the alternatives is the reduction of man power in manufacturing brackets and 10 to 15% weight saving can be expected in additional. This paper ends with some comments about the extension of the present study.

• Journal of architectural history
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• v.14 no.3 s.43
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• pp.103-118
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• 2005

This study is about the meaning of wooden brackets that are distinctive elements of wooden architecture in Korea, Japan, and China. Existing studies about wooden brackets have been limited to the boundary of formalism, so the object of this study is to make a breakthrough in the field of those studies. The Wooden brackets in this study are considered to be decorative elements, and the principles of their design are examined. The specific subject of the study is wooden architecture with Jusimpo-styled brackets that have brackets only on pillars. The definition of Jusimpo is reexamined first, and ChulMok-Ikkong which has not been regarded as a Jusimpo-styled wooden bracket is interpreted as Jusimpo-styled one in this study. Categorized into three types, Jusimpo is examined how it is expressed according to the type of the roof in a building. In view of the results, the wooden bracket system is an effective technique to express the formality, and two designing principles can be seen in Jusimpo; one that wooden brackets observed externally are standardized and regarded as the same ones, and the other that the style of wooden brackets used in the most formal building is Yi-ChulMok. These designing principles mean that the carpenter who was in charge of building the architecture had certain principles when expressing wooden brackets as well as the roofs according to the class of the architecture. In addition, although the styles of wooden brackets that were used in the most formal architecture during the Chosun period were mostly Dapo, Jusimpo in the form of Yi-ChulMok was also adopted in some temples depending on their scale, and that means Jusimpo-styled wooden brackets were never considered to be inferior to Dapo-styled ones. And this point leaves the argument that the reexamination of Jusimpo-styled wooden brackets which have been regarded as the style used in the attached building or small structures since the Choun dynasty should be conducted.

• The korean journal of orthodontics
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• v.49 no.1
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• pp.21-31
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• 2019

Objective: This study was performed to explore the effect of different bracket, archwire, and ligature combinations on resistance to sliding (RS) and rotational control in first-order angulation. Methods: Three types of brackets (multi-level low friction [MLF], self-ligating, and conventional brackets) coupled with four nickel-titanium archwires (0.012, 0.014, 0.016, and 0.018-inch diameter) and two stainless steel ligatures (0.20 and 0.25 mm) were tested in different first-order angulations ($0^{\circ}$, $2^{\circ}$, $4^{\circ}$, $6^{\circ}$, $8^{\circ}$, $10^{\circ}$, $15^{\circ}$, $20^{\circ}$) by using an Instron universal mechanical machine in the dry state at room temperature. RS value was evaluated and compared by one-way ANOVA. Results: Under the same angulation, the RS values showed the following order: conventional brackets > MLF brackets > self-ligating brackets. The RS was the highest for conventional brackets and showed a tendency to increase. The RS for MLF brackets coupled with thinner archwires and ligatures showed a similar tendency as the RS for the self-ligating bracket. In contrast, the RS for MLF brackets coupled with thicker archwires and ligatures increased like that for conventional brackets. MLF brackets showed the greatest range of critical contact angles in first-order angulation. Conclusions: The RS in first-order angulation is influenced by bracket design, archwire, and ligature dimension. In comparison with self-ligating and conventional brackets, MLF brackets could express low friction and rotational control with their greater range of critical contact angles.

• The korean journal of orthodontics
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• v.42 no.6
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• pp.297-306
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• 2012

Objective: This in vitro study was undertaken to evaluate the physical, chemical, and biological properties of commercially available metal orthodontic brackets in South Korea, because national standards for these products are lacking. Methods: Four bracket brands were tested for dimensional accuracy, (manufacturing errors in angulation and torque), cytotoxicity, composition, elution, and corrosion: Archist (Daeseung Medical), Victory (3M Unitek), Kosaka (Tomy), and Confidence (Shinye Odontology Materials). Results: The tested rackets showed no significant differences in manufacturing errors in angulation, but Confidence brackets showed a significant difference in manufacturing errors in torque. None of the brackets were cytotoxic to mouse fibroblasts. The metal ion components did not show a regular increasing or decreasing trend of elution over time, but the volume of the total eluted metal ions increased: Archist brackets had the maximal Cr elution and Confidence brackets appeared to have the largest volume of total eluted metal ions because of excessive Ni elution. Confidence brackets showed the lowest corrosion resistance during potentiodynamic polarization. Conclusions: The results of this study could potentially be applied in establishing national standards for metal orthodontic brackets and in evaluating commercially available products.

• The korean journal of orthodontics
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• v.20 no.2
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• pp.283-291
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• 1990

The purpose of this study was to measure and compare tensile and shear strength for 4 types of new direct-bonding brackets and same brackets after recycling and to evaluate the change of bracket slot width after recycling. Four types of new direct-bond brackets were bonded to recently extracted human premolar teeth and the tensile and shear strength was measured by Universal Testing Machine. The brackets were recycled by chemical process and the tensile and shear test was repeated. To evaluate the change of the bracket slot width, slot width was measured by the Topcon Universal Measuring Microscope before and after recycling. Following results were obtained: 1. There was no satistically significant difference between the tensile and shear strength of recycled brackets and those of new brackets. 2. In both new and recycled brackets, the tensile and shear strength of perforated base bracket was lower than those of photoetched, foilmesh and contou-lok mesh base brackets. (P<0.01) 3. There was no statistically significant difference in bonding strengths of control group bonded only once and two times. 4. There was no statistically significant difference in the change of the bracket slow width after recycling process. 5. Of the failure, the combination type (58%) in the tensile strength and the tooth adhesive interface (65%) in the shear strength was the most common type.

• The korean journal of orthodontics
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• v.22 no.2 s.37
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• pp.327-343
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• 1992

Metal brackets and ceramic brackets were bonded to natural teeth, porcelain crowns and gold crowns After stored in artificial saliva solution for 72 hours at $37^{\circ}C$, the shear bond strengths were measured by Instron and compared with them, the bonding sites and bracket bases were examined by scanning electron microscope and light optical stereomicroscope. The results were as follows: 1. The shear bond strengths of the group which metal brackets were bonded to natural teeth and the groups which ceramic brackets were bonded to natural teeth and porcelain crowns were comparable to each other, the shear bond strength of the group which metal brackets were bonded to gold crowns was significantly low. 2. The bond failed predominantly at the bracket base/adhesive interface with the bulk of adhesive remaining on enamel in the group which metal brackets were bonded to natural teeth. 3. The bond failed consistently at the crown/adhesive interface with all of adhesive remaining on the bracket babes in the group which metal brackets were bonded to gold crowns. 4. The bond failed at the enamel or crown/adhesive interface with the bulk of adhesive remaining on the bracket bases in the groups which cramic brackets were bonded to natural teeth and porcelain crowns. 5. The shear bond strengths of the groups which ceramic brackets were bonded to porcelain crowns were not affected by etching time.