• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.343-349
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• 2004

Laser-aided debonding has advantages in that the heat produced is localized and controlled, the debonding tool is not heated, and it can be used for the removal of various types of ceramic brackets, regardless of their design. However, the range of safe power usage for laser-aided debonding has not vet been confirmed. The Purpose of this study was to evaluate the histologic changes of pulpal tissue in a rabbit's incisor after Nd-YAG laser-aided ceramic bracket debonding at different levels of power. The result were as follows: 1. At 3-5W Nd-YAG laser power level and 3 seconds of exposure time, the ceramic bracket debonding procedure was not easy. At 5W of power a tie-wing fracture occurred on one bracket during debonding using Weingart plier. The histologic section of pulp represented no adverse changes. 2. At 7-13 W power level and less than 5 seconds of exposure time, the debracketing procedure was done easily and bracket facture did not occur. The histologic section of pulp represented mild and reversible changes. All the results were reversible and no pulpal degeneration or necrosis occurred. Considering the results, it appears that the laser-aided debonding technique is a safe method that does not result in irreversible pulpal changes, softens bracket bonding resin within a saie range of power and exposure time, and is useful for ceramic bracket recycling by lowering the tie- wing fracture rate.

• The korean journal of orthodontics
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• v.28 no.4 s.69
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• pp.641-657
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• 1998

This study was undertaken to compare the bond strength and the fracture site of new and recycled brackets according to the base design. 252 sound premolars extracted for orthodontic treatment were collected and Type I, Type II, Type III brackets were divided into four groups by recycling method Each bracket was then bonded to an extracted premolar. Instron Universal Testing Machine(model W) was used to measure the shear bond strength, and the surface of the recycled brackets were viewed in SEM For the analysis of the results, one way ANOVA and Scheffe's multiple range test was executed using the SPSSWIN program. 1. The shear bond strength showed statistically significant difference according to the bracket base design(p<0.001). Type III bracket(round indentation base, micro-etched) showed the highest bond strength, Type I bracket(foil-mesh base) was second, and Type II bracket(grooved integral base, micro-etched) was last. 2. The effect of recycling on the bond strength was different according to bracket type. The shear bond strength of Type I, Type II brackets showed the smallist reduction when treated for 1 minute in Big Jane(p<0.05), but the shear bond strength of Type III brackets showed no statistically significant difference according to recycling method(p>0.05). 3. In Type I, Type II brackets, frequent fracture site was bracket-resin interface, but in Type III brackets, about half of the resin was retained on the tooth surface frequently. 4. The shear bond strength was highest when about half of the resin was retained on the tooth surface(p<0.05). 5. The resin remnant on the bracket base after recycling had no effect on the shear bond strength.

• The korean journal of orthodontics
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• v.41 no.1
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• pp.16-24
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• 2011

Objective: The purpose of this study was to determine (1) the shear bond strength (SBS) of an antimicrobial monomer-containing self-etching primer according to ceramic bracket types and (2) the bracket-adhesive failure mode using an adhesive remnant index (ARI). Methods: A total of 90 extracted human teeth were randomly divided into 6 groups. Each group consisted of one of two ceramic brackets (monocrystalline, polycrystalline) and one of three primers (Transbond XT primer, Transbond Plus SEP, Clearfil Protect Bond) with each group containing 15 specimens. The SBS was measured, and adhesive residues left on the tooth surface were assessed. Results: The SBS of polycrystalline ceramic bracket groups was Significantly higher than that of the monocrystalline ceramic bracket groups (p < 0.001). The SBS of Transbond XT primer groups was significantly higher than those of Transbond Plus SEP groups and Clearfil Protect Bond groups (p < 0.001). All the groups showed bonding failures between the bracket base and adhesive. Conclusions: The combination of a self-etching primer with a monocrystalline bracket is recommended for clinical use, considering its acceptable SBS and mode of failure.

• The korean journal of orthodontics
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• v.39 no.2
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• pp.105-111
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• 2009

Objective: To estimate the effects of bracket material type on enamel decalcification during orthodontic treatment, this study analyzed the adhesion level of mutans streptococci (MS) to orthodontic bracket materials in vivo. Methods: Three different types of orthodontic bracket materials were used: stainless steel, monocrystalline sapphire, and polycrystalline alumina. A balanced complete block design was used to exclude the effect of positional variation of bracket materials in the oral cavity. Three types of plastic individual trays were made and one subject placed the tray in the mouth for 12 hours. Then, the attached bacteria were isolated and incubated on a mitis salivarius media containing bacitracin for 48 hours. Finally, the number of colony forming units of MS was counted. The experiments were independently performed 5 times with each of the 3 trays, resulting in a total of 15 times. Mixed model ANOVA was used to compare the adhesion amount of MS. Results: There was no difference in colony forming units among the bracket materials irrespective of jaw and tooth position. Conclusions: This study suggested that the result of quantitative analysis of MS adhesion to various orthodontic bracket materials in vivo may differ from that of the condition in vitro.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2013.05a
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• pp.953-954
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• 2013

• Magazine of the Korea Concrete Institute
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• v.18 no.4 s.93
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• pp.57-62
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• 2006

• Communications of the Korean Mathematical Society
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• v.22 no.3
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• pp.353-357
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• 2007

Let $(g,\;\delta)$ be a Lie bialgebra. Here we give an explicit formula for the Poisson bracket on a subalgebra of $U(g)^{\circ}$ induced by the given cobracket $\delta$.

• The korean journal of orthodontics
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• v.32 no.6 s.95
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• pp.443-453
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• 2002

The principal aims of this study were to identify the composition of salivary pellicles formed on various orthodontic brackets and to obtain a detailed information about the protein adsorption profiles from whole saliva and two major glandular salivas. Four different types of orthodontic brackets were used. All were upper bicuspid brackets with a $022{\times}028$ slot Roth prescription; stainless steel metal, monocrystalline sapphire, polycrystalline alumina, and plastic brackets. Bracket pelicles were formed by the incubation of orthodontic brackets with whole saliva, submandibular-sublingual saliva, and parotid saliva for 2 hours. The bracket pellicles were extracted and confirmed by employing sodium dodecyl sulfatepolyacrylamide gel electrophoresis, Western transfer methods, and immunodetection. The results showed that low-molecular weight salivary mucin, ${\alpha}-amylase$, secretory IgA (sIgA), acidic proline-rich proteins, and cystatins were attached to all of these brackets regardless of the bracket types. High-molecular weight mucin, which promotes the adhesion of Streptococcus mutans, did not adhere to uy orthodontic brackets. Though the same components were detected in all bracket pellicles, however, the gel profiles showed qualitatively and quantitatively different pellicles, according to the origins of saliva and the bracket types. In particular, the binding of sIgA was more prominent in the pellicles from parotid saliva and the binding of cystatins was prominent in the pellicles from the form plastic brackets. This study indicates that numerous salivary proteins adhere to the orthodontic brackets and these salivary proteins adhere selectively according to bracket types and the types of the saliva.

• The korean journal of orthodontics
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• v.36 no.1 s.114
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• pp.30-44
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• 2006

This study was performed to investigate the location of the ideal bracket positioning plane in lingual orthodontics using the three-dimensional finite element method. Displacement of the anterior teeth were evaluated according to the vertical and the angular movements of the bracket positioning plane. To achieve the ideal movement of anterior teeth in the lingual central plane, the location of the force application point and the amount of the moment applied to the four incisors were evaluated. As the bracket positioning plane was moved parallel toward the incisal edge, uncontrolled tipping and extrusion of the maxillary and the mandibular incisors were increased. But lingual tipping of the crown was decreased in the maxillary and the mandibular canines. As the bracket positioning plane was inclined toward the incisal edge, lingual tipping was increased in the 6 anterior teeth and extrusion of incisors and intrusion of the canine was also increased. As the retraction hook of the canine bracket was elongated, lingual tipping and extrusion of the central incisor and mesial movement and extrusion of the lateral incisor were increased. In the canine, mesial and labial movements of the crown were increased. When the moment was applied to the 4 incisors of the maxillary and the mandibular arch in the lingual central plane, 280 gf-mm in the maxillary central incisor, 500 gf-mm in the maxillary lateral incisor, 170 gf-mm in the mandibular central incisor and 370 gf-mm in the mandibular lateral incisor produced bodily movement of the individual tooth.

• The korean journal of orthodontics
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• v.36 no.3 s.116
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• pp.207-217
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• 2006

Although ceramic brackets have been used widely for improved esthetics during treatment, ceramic brackets have some inherent problems; brittleness, attrition of the opposing teeth and high frictional resistance. This study was performed to understand the frictional resistance of the ceramic brackets, as well as to be a helpful reference for finding the solutions to the problem of frictional resistance. Three different kinds of brackets were used; metal bracket, polycrystalline ceramic brackets with a metal slot to reduce the high frictional resistance and monocrystalline ceramic brackets. The brackets were tested with a $.019{\times}.025$ stainless steel wire with a second order angulation of $0^{\circ}\;and\;10^{\circ}$, and the static and kinetic frictional forces were measured on the universal testing machine. The results of this study showed that the ceramic brackets, especially the monocrystalline ceramic bracket without a metal slot, generated higher frictional resistance than the metal bracket, and the frictional resistance was increased as the angulation between the bracket slot and the wire increased. Therefore, the development of the ceramic bracket with reduced frictional resistance and the prevention of excessive crown tipping during orthodontic treatment will lead to the simultaneous attainment of more efficient and improved esthetic treatment goals.