• The korean journal of orthodontics
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• v.34 no.4 s.105
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• pp.303-312
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• 2004

An unfavorable tipping movement can occur during the retraction of anterior teeth because orthodontic force is loaded by brackets positioned far from the center of resistance. To avoid this unfavorable movement, a compensating curved wire or lingual root torque wire is used. The purpose of this study is to investigate, using photoelastic material, the distribution of initial stress associated with the retraction of the incisors according to the degree of the compensating curve, to model changes associated with tooth ud alveolar bone structure. The following results were obtained by analysis of the polarizing plate of the effects of initial stress resulting from retraction of the anterior teeth: 1. When the incisors were retracted using combination archwire or sliding mechanics, the maximal polarizing pattern of the apical area decreased as the degree of the compensating owe increased from 0 to 15 to 30. 2. When the incisors were retracted by the combination archwire or sliding mechanics, the maximal polarizing pattern of the canine and premolar area increased as the degree of the compensating curve increased from 0to 15to 30. 3. A lower degree of polarizing patterns were associated with the combination archwire technique than the sliding mechanics technique at a given force. The above results indicate that there is no significant difference between the combination loop archwire technique and sliding mechanics, for the retraction of maxillary anterior teeth with decreased lingual tipping tendency by a compensating curve on the arch wire. However, the use of sliding mechanics is more effective for the prevention of lingual inclination of the anterior teeth, because the hook used in sliding mechanics is closer to the center of resistance of the maxillary anterior teeth.

• Journal of Surface Science and Engineering
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• v.41 no.5
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• pp.232-239
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• 2008

The dental orthodontic mini-screw requires good mechanical properties and high corrosion resistance for implantation in the bone. The purpose of this study was to investigate the electrochemical characteristics of TiN and ZrN coated orthodontic mini-screws, mini-screws were used for experiment. Ion plating was carried out for mini-screw using Ti and Zr coating materials with nitrogen gas. Ion plated surface of each specimen w as o bserved with f ield emission scanning e lectron microscopy ( FE-SEM), e nergy dispersive x-ray spectroscopy (EDX), and electrochemical tester. The surface of TiN and ZrN coated mini-screw were more smooth than that of other kinds of non-coated mini-screw due to dercrease of machined defects. The corrosion current density of the TiN and ZrN coated mini-screw decreased compared to non-coated sample. The corrosion potential of TiN and ZrN coated mini-screw were higher than that of non-coated mini-screw in 0.9% NaCl solution. The pitting corrosion resistance increased in the order of ZrN coated, TiN coated and non-coated wire. Pitting potential of ZrN coated mini-screw was the highest in the other specimens.

• Journal of Surface Science and Engineering
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• v.41 no.5
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• pp.226-231
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• 2008

Titanium and its alloy have been widely used in dental implant and orthopedic prostheses. Electrochemical characteristics of dental implant in the various simulated body fluids have been researched by using electrochemical methods. Ti-6Al-4V alloy implant was used for corrosion test in 0.9% NaCl, artificial saliva and simulated body fluids. The surface morphology was observed using scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDX). The electrochemical stability was investigated using potentiosat (EG&G Co, 263A). The corrosion surface was observed using scanning electron microscopy (SEM). From the results of potentiodynamic test in various solution, the current density of implant tested in SBF and AS solution was lower than that of implant tested in 0.9% NaCl solution. From the results of passive film stability test, the variation of current density at constant 250 mV showed the consistent with time in the case of implant tested in SBF and AS solution, whereas, the current density at constant 250mV in the case of implant tested in 0.9% NaCl solution showed higher compared to SBF and AS solution as time increased. From the results of cyclic potentiodynamic test, the pitting potential and |$E_{pit}\;-\;E_{corr}$| of implant tested in SBF and AS solution were higher than those of implant tested in 0.9% NaCl solution.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.12 no.3
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• pp.199-209
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• 2014

Crevice corrosion tests were conducted to examine the corrosion properties of HYBRID (HYdrazine Base Reductive metal Ion Decontamination) which was developed to decontaminate the PWR primary coolant system. To compare the corrosion properties of HYBRID with commonly existing decontamination agents, oxalic acid (OA) and citric oxalic acid (CITROX) were also examined. Type 304 Stainless Steel (304 SS) and Alloy 600 which are major components of the primary coolant system in Pressurized Water Reactor (PWR) were evaluated. Crevice corrosion tests were conducted under very aggressive conditions to confirm quickly the corrosion properties of primary coolant system structure components which have high corrosion resistance. Pitting and IGA were occurred in crevice surface under OA and CITROX conditions. But localized corrosion was not observed under HYBRID condition. Very low corrosion rate of less than $1.3{\times}10^{-3}{\mu}m/h$ was observed under HYBRID condition for both materials. On the other hand, under OA condition, Alloy 600 indicated comparatively uniform corrosion rate of $4.0{\times}10^{-2}{\mu}m/h$ but 304 SS indicated rapid accelerated corrosion in lower case than pH 2.0. In case of HYBRID condition, general corrosion and crevice corrosion were scarcely occurred. Therefore, material integrity of HYBRID in decontamination of primary coolant system in pressurized water reactor (PWR) reactor was conformed.

• Journal of Plant Biotechnology
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• v.44 no.4
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• pp.379-387
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• 2017

Various sizes (0.2 ~ 1.2 mm) and developmental stages (referred to as Stage 1 ~ 3) of apical and lateral meristems were excised, together or separately, directly from dormant buds of apple 'Hongro'. They were mixed infected by Apple scar skin viroid (ASSVd), Apple chlorotic leaf spot virus (ACLSV), Apple stem pitting virus (ASPV) and Apple stem grooving virus (ASGV), which are major viruses attacking apples. A total of 31 callus lines (> 10 mm in diameter) were obtained by culturing the explants on Murashige and Skoog (MS) medium supplemented with 3% sucrose, 3.0 mg/L benzyladenine (BA) and 0.1 mg/L indole-3-butyric acid (IBA), and they were subjected to RT-PCR analysis for virus detection. A high rate of virus elimination (expressed as the percentage of calli that did not amplify during RT-PCR, i.e., RT-PCR negative calli per total number of calli obtained) was achieved for ACLSV (100%), ASSVd (93.7%), and ASPV (93.7%), whereas it was only 25.8% for ASGV. ASPV was detected in the presence of 2 ~ 3 bracts. Simultaneous virus elimination of ASSVd, ASPV, ACLSV, and ASGV occurred during the meristem culture, in which the early stages of the dormant buds (Stage 1) were used, because ASGV was mostly eliminated during that stage. The results of the present study will be valuable for the production of virus-free apple trees.

• The Plant Pathology Journal
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• v.33 no.6
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• pp.561-571
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• 2017

Prospecting of local grapevine (Vitis vinifera L.) germplasm revealed that Tunisia possesses a rich patrimony which presents diversified organoleptic characteristics. However, viral diseases seriously affect all local grapevine cultivars which risk a complete extinction. Sanitation programs need to be established to preserve and exploit, as a gene pool, the Tunisian vineyards areas. The presence of the Grapevine leafroll associated virus-3 (GLRaV-3), Grapevine stem pitting associated virus (GRSPaV) and Grapevine virus A (GVA), were confirmed in a Tunisian grapevine cultivar using serological and molecular analyses. The association between GRSPaV and GVA viruses induces more rugose wood symptoms and damages. For this reason the cleansing of the infected cultivar is highly advisable. Direct and recurrent somatic embryos of cv. 'Hencha' were successfully induced from filament, when cultured on $Ch{\acute{e}}e$and Pool (1987). based-medium, enriched with $2mg1^{-1}$ of 2,4-dichlorophenoxyacetic acid and $2.5mg1^{-1}$ of Thidiazuron, after 36 weeks of culture. After six months of acclimatization, RT-PCR carried on 50 somaplants confirmed the absence of GVA, GRSPaV as well as GLRaV-3 viruses in all somaplants. Ampelographic analysis, based on eight OIV descriptors, was carried out on two years acclimated somaplants, compared to the mother plant. Results demonstrated that the shape and contours of 46 somaclones leaves are identical to mother plant leaves and four phenotypically off-type plants were observed. The healthy state of 100% 'Hencha' somaclones and the high percentage of phenotypically true-to-type plants demonstrate that somatic embryogenesis is a promising technique to adopt for grapevine viruses elimination.

• Journal of the korean academy of Pediatric Dentistry
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• v.28 no.1
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• pp.175-179
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• 2001

Regional odontodysplasia is a relatively rare condition in which both enamel and dentin are hypoplastic and hypocalcified. The result is localized arrest in tooth development. The etiology of regional odontodysplasia is uncertain, but, disturbance in vascular supply, somatic mutation, latent virus infection, trauma, hyperpyrexia, irradiation, nutrition, metabolic disorders and hereditary transmission are supported to be etiologic factors. Females are more often affected than males. (1.4 : 1). The maxillary arch is more often affected than the mandibular arch with the maxillary left quadrant being the most commonly involved. Affected teeth are hypoplastic, typically discolored yellow or yellowish brown, smaller in size and display a variety of surface marking including pitting and grooving. Radiographically, the teeth affected have been described to have a "ghost like" appearance or "fuzzy" appearance. Pulp calcification and denticles may be present within the pulp chambers of the affected teeth. In it's case, a 2 years old male visited for a treatment of uneruption of lower right teeth. Partial eruption of lower right deciduous central incisor and unerupted deciduous lateral incisor, deciduous canine and deciduous first molar showed severly delayed eruption state. On radiographic appearance, "Ghost like appearance", shortened root and opened apexes on lower right region were observed. It was suspected regional odontodysplasia with clinical and radiographic condition.

• Research in Plant Disease
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• v.26 no.2
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• pp.95-102
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• 2020

The investigation of the infection rate of domestic apple orchards by four types of apple viruses (Apple chlorotic leaf spot virus [ACLSV], Apple stem pitting virus [ASPV], Apple stem grooving virus [ASGV], Apple mosaic virus [ApMV]) and one type of viroid (Apple scar skin viroid, ASSVd) found that most apple trees were infected with viruses and viroid at the rate of 97.3%. By region, the infection rate in Jeongseon stood at 98.8%, Danyang at 100%, Yesan at 100%, Jangsu at 89.1%, and Muju at 98.1%. By each virus and viroid, the infection rate of ASGV was the highest at 93.4%, followed by ASPV at 85.7%, ACLSV at 59.0%, ASSVd at 6.7%, and ApMV at the lowest 3.6%. In addition, 84.8% of the cases were infected with two or more types of viruses and viroid, nearly seven times the single type infection rate of 12.4%, and the cases infected with three viruses, ASPV, ACLSV, and ASGV accounted for 56.2%, more than the half the total number of trees investigated.

• The korean journal of orthodontics
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• v.30 no.4 s.81
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• pp.453-465
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• 2000

The purpose of this study was to investigate the change of mechanical properties, surface topography and frictional force of various nickel titanium wires after recycling. Three types of nickel-titanium wires and one type of stainless steel wire were divided to three groups: as-received condition(T0:control group), treated in artificial saliva for four weeks(T1) and autoclaved after being treated in artificial saliva(T2). Some changes were observed for the selected mechanical properties in tensile test, surface topography by means of SEM and 3D profilogram, and frictional coefficient. The findings suggest that: 1. Nickel-titanium wires demonstrated no statistically significant differences in maximum tensile strength, elongation rate and modulus of elasticity, but stainless steel wire demonstrated statistically significant differences in maximum tensile strength, elongation rate and modulus of elasticity between the groups(p<0.05). 2. NiTi, Optimalloy, Stainless Steel wires demonstrated increased pitting and corrosion in SEM finding. 3. Recycled NiTi, Optimalloy and stainless steel wires demonstrated significantly greater surface roughness(Ra and Rq) through 3D profilogram when compared with the control wires(p<0.05), but Sentalloy didn't demonstrate significant difference. 4. Recycled NiTi, Optimalloy and stainless steel wires demonstrated significantly greater maximum frictional coefficient when compared with the control wires(p<0.05), but Sentalloy didn't demonstrate significant difference The changes of surface roughness and frictional coefficient in NiTi and Optimalloy had no clinical implication. Consequently recycled nickel titanium wires demonstrated no clinical problem in tensile properties, surface topography and frictional coefficient.

• Korean Journal of Metals and Materials
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• v.47 no.2
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• pp.129-137
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• 2009

Corrosion behaviors of TiN coated dental casting alloys have been researched by using various electrochemical methods. Three casting alloys (Alloy 1: 63Co-27Cr-5.5Mo, Alloy 2: 63Ni-16Cr-5Mo, Alloy 3: 63Co-30Cr-5Mo) were prepared for fabricating partial denture frameworks with various casting methods; centrifugal casting(CF), high frequency induction casting(HFI) and vacuum pressure casting(VP). The specimens were coated with TiN film by RF-magnetron sputtering method. The corrosion behaviors were investigated using potentiostat (EG&G Co, 263A. USA) in 0.9% NaCl solution at $36.5{\pm}1^{\circ}C$. The corrosion morphologies were analyzed using FE-SEM and EDX. Alloy 1 and Alloy 2 showed the ${\alpha}-Co$ and ${\varepsilon}-Co$ phase on the matrix, and it was disappeared in case of TiN coated Alloy 1 and 2. In the Alloy 3, $Ni_2Cr$ second phases were appeared at matrix. Corrosion potentials of TiN coated alloy were higher than that of non-coated alloy, but current density at passive region of TiN coated alloy was lower than that of non-coated alloy. Pitting corrosion resistances were increased in the order of centrifugal casting, high frequency induction casting and vacuum pressure casting method from cyclic potentiodynamic polarization test.