• Proceedings of the KACD Conference
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• 2008.05a
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• pp.177-183
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• 2008

It was reported that esthetic composite resin restoration reinforces the strength of remaining tooth structure with preserving the natural tooth structure. However, it is unknown how much the strength would be recovered. The purpose of this study was to compare the fracture resistance of three types of undermined cavity filled with composite resin with that of non-cavitated natural tooth. Forty sound upper molars were allocated randomly into four groups of 10 teeth. After flattening occlusal enamel. undermined cavities were prepared in thirty teeth to make three types of specimens with various thickness of occlusal structure (Group $1{\sim}3$). All the cavity have the 5 mm width mesio-distally and 7 mm depth bucco-lingually. Another natural 10 teeth (Group 4) were used as a control group. Teeth in group 1 have remaining occlusal structure about 1 mm thickness, which was composed of mainly enamel and small amount of dentin. In Group 2, remained thickness was about 1.5 mm, including 0.5 mm thickness dentin. In Group 3, thickness was about 2.0 mm, including 1 mm thickness dentin. Every effort was made to keep the remaining dentin thickness about 0.5 mm from the pulp space in cavitated groups. All the thickness was evaluated with radiographic Length Analyzer program. After acid etching with 37% phosphoric acid, one-bottle adhesive (Single $Bond^{TM}$, 3M/ESPE, USA) was applied following the manufacturer's recommendation and cavities were incrementally filled with hybrid composite resin (Filtek $Z-250^{TM}$, 3M/ESPE, USA). Teeth were stored in distilled water for one day at room temperature, after then, they were finished and polished with Sof-Lex system. All specimens were embedded in acrylic resin and static load was applied to the specimens with a 3 mm diameter stainless steel rod in an Universal testing machine and cross-head speed was 1 mm/min. Maximum load in case of fracture was recorded for each specimen. The data were statistically analyzed using one-way analysis of variance (ANOVA) and a Tukey test at the 95% confidence level. The results were as follows: 1. Fracture resistance of the undermined cavity filled with composite resin was about 75% of the natural tooth. 2. No significant difference on fracture loads of composite resin restoration was found among the three types of cavitated groups. Within the limits of this study, it can be concluded the fracture resistance of the undermined cavity filled with composite resin was lower than that of natural teeth, however remaining tooth structure may be supported and saved by the reinforcement with adhesive restoration, even of that portion consists of mainly enamel and a little dentin structure.

• Restorative Dentistry and Endodontics
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• v.33 no.3
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• pp.177-183
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• 2008

It was reported that esthetic composite resin restoration reinforces the strength of remaining tooth structure with preserving the natural tooth structure. However, it is unknown how much the strength would be recovered. The purpose of this study was to compare the fracture resistance of three types of undermined cavity filled with composite resin with that of non-cavitated natural tooth. Forty sound upper molars were allocated randomly into four groups of 10 teeth. After flattening occlusal enamel, undermined cavities were prepared in thirty teeth to make three types of specimens with various thickness of occlusal structure (Group $1{\sim}3$). All the cavity have the 5 mm width mesiodistally and 7 mm depth bucco-lingually. Another natural 10 teeth (Group 4) were used as a control group. Teeth in group 1 have remaining occlusal structure about 1 mm thickness, which was composed of mainly enamel and small amount of dentin. In Group 2, remained thickness was about 1.5 mm, including 0.5 mm thickness dentin. In Group 3, thickness was about 2.0 mm, including 1 mm thickness dentin. Every effort was made to keep the remaining dentin thickness about 0.5 mm from the pulp space in cavitated groups. All the thickness was evaluated with radiographic Length Analyzer program. After acid etching with 37% phosphoric acid, one-bottle adhesive (Single $Bond^{TM}$, 3M/ESPE, USA) was applied following the manufacturer's recommendation and cavities were incrementally filled with hybrid composite resin (Filtek $Z-250^{TM}$, 3M/ESPE, USA). Teeth were stored in distilled water for one day at room temperature, after then, they were finished and polished with Sof-Lex system. All specimens were embedded in acrylic resin and static load was applied to the specimens with a 3 mm diameter stainless steel rod in an Universal testing machine and cross-head speed was 1 mm/min. Maximum load in case of fracture was recorded for each specimen. The data were statistically analyzed using one-way analysis of variance (ANOVA) and a Tukey test at the 95% confidence level. The results were as follows: 1. Fracture resistance of the undermined cavity filled with composite resin was about 75% of the natural tooth. 2. No significant difference in fracture loads of composite resin restoration was found among the three types of cavitated groups. Within the limits of this study, it can be concluded the fracture resistance of the undermined cavity filled with composite resin was lower than that of natural teeth, however remaining tooth structure may be supported and saved by the reinforcement with adhesive restoration, even if that portion consists of mainly enamel and a little dentin structure.

• Restorative Dentistry and Endodontics
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• v.27 no.4
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• pp.382-388
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• 2002

Compomer is composed of matrix and filler : matrix is made of the combination of resins and polycarboxylic molecules that are light-cured, and a filler is a glass component which is capable of ion-release. The resin content of compomers produces polymerization shrinkage which can adversely affect marginal adaptation. Pretreatment is a fundamental step which is treated with conditioner or primer in the use of these materials. Microleakage of restorative materials has been investigated mostly by dye penetration method. Dye penetration method was not quantitative and not measured repeatedly. Fluid filtration method, introduced and developed by Pashley's group, has been extensively used for 20 years for research purpose to understand the physiology of dentin, as well as the effects of various restorative treatments on dentin permeability. It permits quantitative, nondestructive measurment of microleakage in a longitudinal manner. The purpose of this study was to evaluate the change of dentin permeability according to the process of compomer restoration. In this study. Cl V cavities were prepared on buccal surface of thirty extracted human molars. The prepared cavities were etched by 37% phosphoric acid. The experimental teeth were randomly divided into three groups. Each group was treated with following materials Group 1 : Prime & Bond NT/Dyract AP, Group2： Single Bond/F2000 compomer, Group 3 : Syntac Single Component/Compoglass. The bonding agent and compomer were applied for each group following manufacturers information. Dentin permeability of each group was measured at each process by fluid filtration method; Step 1 : preparation(smear layer). Step 2 : etching(smear layer removal), Step 3 : applying the bonding agent, Step 4 : filling the compomer. Dentin permeability was expressed by hydraulic conductance ($\mu\textrm{l}$ min$^{-1}$cm$H_2O$$^{-1}$). The data were analysed statistically using One-way ANOVA and Sheffe's method. The results were as follows : 1. Dentin permeability differences between each process were significant except between step 1 and step 2(p<0.01). 2. Dentin permeability after removal of smear layer was highly increased(p<0.01). 3. In most case, decrease of dentin permeability was obtained by applying bonding agent(p<0.01). 4. Dentin permeability differences among the experimental groups were not significant(p>0.05). 5. None of compomers used in this study showed perfect seal at the interface.

• The Journal of Korean Academy of Prosthodontics
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• v.53 no.3
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• pp.234-243
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• 2015

Developing of digital technique, it is possible to fabricate implant prostheses for edentulous area using intraoral 3-dimentional information throughout implant diagnosis and treatment process. It is being changed that from the method using CAD/CAM, producing prostheses by model scanning after conventional impression and model processing, to the method of fabricating implant provisional restorations and customized abutments by digital impression after connecting digital impression copings (scanbody) and implant fixtures without models. But, this digital method has not been actively used for implant prostheses not yet. Specially, it is short of intraoral digital impression cases for immediate provisional restorations of the maxillary anterior implants. The gingival contour impression of maxillary anterior area is very important for esthetic restorations. Accordingly, in this case report, the using a digital impression coping (scanbody) and digital impression by CEREC Omnicam (Sirona, Bensheim, Germany) or Trios (3shape, Copenhagen, Denmark) were introduced for immediate provisional restorations in 3 cases needed a single implant restoration in maxillary anterior area. The clinical results were satisfactory on the convenience and accuracy of digital impression technique and the good esthetics of final restorations.

• Restorative Dentistry and Endodontics
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• v.32 no.3
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• pp.198-207
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• 2007

The purpose of this study was to investigate the effect of calcium hydroxide on dentin bonding strength of various dentin bonding systems as a function of time in composite resin restoration. Dentin adhesives used in this study were Scotchbond Multipurpose, Single Bond, SE Bond and Prompt L-Pop. Flat dentin surfaces adjacent to pulp chamber were created, then $Ca(OH)_2$ and saline were mixed and applied on dentin surface of experimental group, then IRM was used to cover the mixture on dentin surface and the specimens were stored at $36.5^{\circ}C$ for experiment period (7 days, 30 days). After removing IRM and $Ca(OH)_2$, each dentin adhesives were treated on dentin surfaces. Composite resin (Z-250, 3M) was placed with S mm height and was light-cured for 20 seconds. After stored in distilled water for 24 hours, each dentin-composite bonded spicemen was embedded in epoxy resin and sectioned into $1.0\times1.0mm^2$ cross section composite-dentin beams. Specimen was mounted on zig of Universal testing machine and ${\mu}TBS$ test was performed. SEM analysis was performed to examine the fractured surfaces. The results suggested that applying calcium hydroxide did not show significant difference in dentin bonding strength.

• Plant Breeding and Biotechnology
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• v.5 no.3
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• pp.243-251
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• 2017

Rhus chinensis is a shrub widely distributed in Asia. It has been used for traditional medicine and ecological restoration. Here, we report the complete chloroplast genome sequence of two R. chinensis genotypes collected from China and Korea. The assembled chloroplast genome of Chinese R. chinensis is 149,094 bp long, consisting of a large single copy (97,246 bp), a small single copy (18,644 bp) and a pair of inverted repeats (16,602 bp). Gene annotation revealed 77 protein coding genes, 30 tRNA genes, and 4 rRNA genes. A phylogenomic analysis of the chloroplast genomes with 11 known complete chloroplast genomes clarified the relationship of R. chinensis with the other plant species in the Sapindales order. A comparative chloroplast genome analysis identified 170 SNPs and 85 InDels at intra-species level of R. chinensis between Chinese and Korean collections. Based on the sequence diversity between Korea and Chinese R. chinensis plants, we developed three DNA markers useful for genetic diversity and authentication system. The chloroplast genome information obtained in this study will contribute to enriching genetic resources and conservation of endemic Rhus species.

• Conservation Science in Museum
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• v.30
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• pp.1-22
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• 2023

This study aims to document the conservation treatment of the fine-hemp official headgear housed by the National Museum of Korea, and to reconsider its existing name following the restoration of the original form of the damaged cultural heritage asset. The headgear consists of a single inner frame with a vertical line at the front, a single outer frame surrounding the inner frame, and a double-layered headband that spans the circumference of the wearer's head and joins the inner and the outer frames. This study applied a conservation treatment to the men's undyed hemp headgear of the Joseon Dynasty in order to remove contaminants and foreign substances on the surface and repair the partially deteriorated and damaged fabric, thereby restoring and stabilizing the original shape and preparing it for exhibitions. The hemp headgear was sewed both by hand and with a sewing machine. Although its overall composition and style are similar to the same type of official headgear from the Joseon Dynasty, the use of a sewing machine supports the assumption that it was produced in the early 1900s. This study identified similarities between the overall composition and shape of the fully-preserved hemp official headgear and those of the jangbogwan, a type of men's official headgear worn by Confucian scholars as part of their everyday attire, and compared it with the shape of jangbogwan seen in documentary records, illustrations, prior research, and portraits from the Joseon Dynasty, as well as with the characteristics of extant jangbowan artifacts, eventually concluding that it is appropriate to classify and name the headgear as a jangbogwan.

• The Journal of Korean Academy of Prosthodontics
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• v.56 no.3
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• pp.212-217
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• 2018

Purpose: This study was to assess clinically the incidence of abutment screw loosening of posterior implant-supported fixed prosthesis and its affecting factors. Materials and methods: 391 implant-supported crowns restored from January 2013 to January 2016 were included in this study. All restorations were fabricated with either a single crowns or a splinted crown, and cemented with temporary cement. The incidence of abutment screw loosening is investigated and gender, restoration position, opposing teeth, restoration type, abutment connection type were assessed as possible factors affecting abutment screw loosening. Results: During the observation period (2 - 5 years), abutment screw loosening was found in 29 restorations (7.4%). It took 3 to 48 months (means 19.5 months) to loose the screw, and three of these implants were fractured. Among the factors considered, there were statistically significant differences at abutment screw loosening rate between molar group (9.4%) and premolar group (2.6%) (P<.019). According to the type of opposing teeth, there were statistically significant differences between nature teeth (74.7%) and implant (25.0%), removable denture (3%) (P<.019). The other possible factors did not have a significant effect on loosening of the abutment. Conclusion: The incidence of abutment screw loosening in posterior restoration was 7.4%. Abutment screw loosening were more likely to occur in molars group than premolar group, and according to the opposing teeth, there were the greatest frequency in nature teeth than implant and removal denture. There was a statistically significant difference.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.4B
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• pp.361-367
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• 2011

The channel-forming discharge, which is a standard and single flow for the river maintenance and restoration project, should be estimated necessarily in the stable channel design. It is difficult to produce the specific pattern for the channel-forming discharge in the domestic rivers due to the insufficient researches and case studies. Also, it is improper to adopt the foreign cases for the domestic rivers and streams which have the high coefficients of river regime. Therefore, the channel-forming discharge possible to use for rivers with high coefficients of river regime is suggested in this study through analyzing the bankfull, specified recurrence interval, and effective discharges of Mangyeong River, Cheongmi Stream, and Hampyeong Stream for the abandoned channel restoration project. The bankfull discharge was calculated with geometric data using the HEC-RAS modeling and the flow, bed materials, and sediment data for the study reaches were used to estimate the specified recurrence interval and effective discharges. As a result for calculating the channel-forming discharge, the effective discharge was greater than the bankfull discharge in the river with high coefficient of river regime and the effective discharge was greater than the bankfull and there was no correlation between the coefficient of river regime and the characteristics of the specified recurrence interval discharges.

• Restorative Dentistry and Endodontics
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• v.27 no.3
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• pp.249-256
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• 2002

The use of flowable composite resins as liners in class II packable composite restoration has been suggested by some manufacturers. However, the contributions of this technique are unproven. The purpose of this study was to compare the gingival microleakage in class II packable composite restorations with or without the use of flowable composite resins as liners. Slot cavities were prepared on both proximals of 80 extracted human molars and randomly assigned to 8 groups of 20 each. The gingival margins were located at 1mm above CEJ in 80 cavities (group1-4) and 1mm below CEJ in 80 cavities (group5-8). The prepared teeth were mounted in the customized tray with adjacent teeth to simulate clinical conditions and metallic matrix band (Sectional matrix) and wooden wedges were applied. After acid etching and application of Single Bond, each group was restored with the following materials using incremental placement technique: Group 1,5 (Filtek P60), group 2, 3, 4 and group 6, 7, 8 (AeliteFlo, TetricFlow, Revolution/ Filtek P60). All specimens were thermocycled 500 times between 5$^{\circ}C$ and 55$^{\circ}C$ with 1 mimute dwell time, immersed 2% methylene blue dye for 24 hours and then rinsed with tab water. The specimens were embedded in clear resin and sectioned longitudinally through the center of restoration with a low speed diamond saw. Dye penetration at gingival margin was viewed at 20 magnification and analyzed on a scale of 0 to 4. Kruscal-Wallis One way analysis and Mann-Whitney Rank sum test were used to analyze the results. The results of this study were as follows. 1. The leakage values seen at the enamel margin were significantly lower than those seen at the dentin margin(P<0.05). 2. On the enamel margin, packable composite resins with flowable liners showed lower leakage than those without flowable liners, but there were no significant differences among the four groups(P>0.05). 3. On the dentin margin, four groups demonstrated moderate to severe leakage, and there were no significant differences in leakage values(P>0.05).