• Restorative Dentistry and Endodontics
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• v.34 no.1
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• pp.8-19
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• 2009

The purpose of this study was to investigate the effects of four restorative materials under various occlusal loading conditions on the stress distribution at the CEJ of buccal. palatal surface and central groove of occlusal surface of endodontically treated maxillary second premolar, using a 3D finte element analysis. A 3D finite element model of human maxillary second premolar was endodontically treated. After endodontic treatment, access cavity was filled with Amalgam, resin, ceramic or gold of different mechanical properties. A static 500N forces were applied at the buccal (Load-1) and palatal cusp (Load-2) and a static 170N forces were applied at the mesial marginal ridge and palatal cusp simultaneously as centric occlusion (Load-3). Under 3-type Loading condition, the value of tensile stress was analyzed after 4-type restoration at the CEJ of buccal and palatal surface and central groove of occlusal surface Excessive high tensile stresses were observed along the palatal CEJ in Load-1 case and buccal CEJ in Load-2 in all of the restorations. There was no difference in magnitude of stress in relation to the type of restorations. Heavy tensile stress concentrations were observed around the loading point and along the central groove of occlusal surface in all of the restorations. There was slight difference in magnitude of stress between different types of restorations. High tensile stress concentrations around the loading points were observed and there was no difference in magnitude of stress between different types of restorations in Load-3.

• Korea journal of population studies
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• v.33 no.3
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• pp.1-30
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• 2010

This study examines difference in age at marriage between spouses and more importantly, investigates into the economic and social factors affecting the ratio or probability of wife-older marriages. Empirical analysis is carried out by applying both logit model and multinomial logit model to an independently pooled cross-section over 2004-2007. The data was collected mainly from the micro data service system of the Statistics Korea. Empirical results indicate that a wife-older marriage was more likely as a wife was more educated and was a larger income earner than a husband. On the other hand, a wife's educational and income level themselves had few systematic relationships with the probability of a wife-older marriage. The probability of a wife-older marriage tended to decrease(increase) when a husband's(a wife's) marriage was the second' The study calculates the average marginal effect of difference in the income level between spouses on the probability of a wife-older marriage, which is -0.007. That is, the probability of a wife-older marriage increases by 0.7% as a husband's income level is 1 million Korean Won less than a wife's. This results presents empirical evidence against widely distributed misconception on wife-older marriage in the mass media.

• Journal of Periodontal and Implant Science
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• v.23 no.3
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• pp.374-390
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• 1993

Regeneration of periodontal tissue after a loss of attachment due to disease or trauma repesents an important issue in dentistry, and various bone graft materials have been used to regenerated lost periodontal tissue and restore proper fuctions. Among those, allografts have been extensively researched and widely used clinically, since they are known to possess an excellent osteoinduction capability and result in proper topography of alveolar bone. Regeneration of periodontal tissue in supraalveolar defects may be technically difficult. However, a large amount of regeneration has been observed by complete tissue coverage of involved teeth. In this study, supraalveolar defects in adult dogs were treated with periodontal surgery, decalcified freez-dried bone allograft, complete tissue coverage was attained, and effects on repair and regeneration of alveolar bone, cementum and periodontal ligament were studied. Exposure of premolar furcation of adult dogs was attained by removing marginal alveolar bone down to 5mm from CEJ, and root surfaces were planed with curettes. On the left side, defects were treated without any allograft(Control Group). On the right side, a DFDB was used(Experimental Group). In all groups, flaps were coronally positioned and sutured, completely submerging the treated defects. At two weeks, the crown were exposed 2-3mm. Healing progresses were histologically observed after eight weeks and the results were as follows : 1. Distance from CEJ to AJE was : $2.82{\pm}0.66mm$ in the control group, $1.71{\pm}0.51mm$ in experimental group, with significant differences between groups.(P<0.01) 2. Periodontal repair was : $2.18{\pm}0.66mm$ in the control group, $3.29{\pm}0.51mm$ in experimental group, with significant differences between groups.(P<0.01) 3. Connective tissue repair was : $1.43{\pm}0.52mm$ in the control group, $0.76{\pm}0.47mm$ in experimental group, with significant differences between groups.(P<0.01) Orientation of connective tissue fibers in relation to root surfaces was : mostly parallel in the control group, vertical or parallel or irregular in experimental group. 4. The amount of cementum formation was : $1.66{\pm}0.58mm$ in the control group, $2.86{\pm}0.66mm$ in experimental group, with significant differences between groups. 5. The amount of alveolar bone formation was : $0.76{\pm}0.72mm$ in the control group, $2.53{\pm}0.56mm$ in experimental group, with significant differences between groups.(P<0.01)

• Journal of the korean academy of Pediatric Dentistry
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• v.30 no.4
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• pp.593-599
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• 2003

The purposes of this study were to evaluate the microleakage of class V composite resin restorations utilizing the different curing lights, to assess the flowable resin, $Filtek^{TM}Flow$(3M Dental Products, USA) and composite resin, $Filtek^{TM}Z250$(3M Dental Products, USA) which need 20s curing time for halogen light could replace $Z100^{TM}$ Restorative(3M Dental Products, USA) for the microleakage, and to evaluate the effect of adhesive resin on marginal microleakage. Light curing units used in this study were conventional halogen light, XL3000(3M Dental Products, USA) and plasma arc light, Flipo(Lokki, France). Class V cavities were prepared and each cavity was filled with each composite resin. After being filled, the teeth were stored in distilled water, polished, thermocycled and soaked in 1% methylene blue solution. Following results were obtained from evaluation of the sectioned surface. 1. There was no statistically significant difference in microleakage of $Filtek^{TM}Flow$ and $Filk^{TM}Z250$ between two kinds of curing units(p>0.05). 2. Flowable resin, $Filtek^{TM}Flow$ showed more microleakage than Z100 and $Filtek^{TM}Z250$ regardless of curing units(p<0.05). 3. Adhesive resin reduced the microleakage of composite resin in both halogen light and plasma arc light(p<0.05).

• Journal of Dental Rehabilitation and Applied Science
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• v.16 no.2
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• pp.113-122
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• 2000

The reinforced composte resin as the esthetic operative material continuously has been studied because the porcelain fused metal prosthesis is widely used for its excellent esthetics, rigidity and marginal integrity, but it has low fracture resistance against the tensile strength and stress, attrition of the opposite teeth. The reinforced composite resin is well adapt with the dental alloy but it is low the shear bond strength with the dental alloy vs the porcelain fused metal prosthesis, and then has been studied continuously. The purpose of the study was to examine how metal was the higher shear bond strength among the dental alloy was used to the reinforced composite resin and to find the effect that the particle size of sandblasting influenced the shear bond strength. We built up the reinforced composite resin with 4 mm in diameter, 3 mm in height on circular alloy with 5 mm in diameter, 2 mm in height. Type II gold, type IV gold, and Ag-Pd alloy was used as alloys and $50{\mu}m$, $110{\mu}m$, $250{\mu}m$ of the particle size was sandblasted at each alloy in bonding between alloy and resin. We made 90 secimens of 10 per each group and we measured the shear bond strength using the Instron($M100EC^{(R)}$, Mecmesin Co., England). The obtained results were as follows : 1. In comparison among each alloys, Ag-Pd alloy had the highest shear bond strength and the shear bond strength was decreased significantly in the sequence of the type II gold and type IV gold(P<0.001). 2. In comparison according to the size of sandblasting particle, (1) In Ag-Pd alloy, shear bond strength was decreased in the sequence of $110{\mu}m$, $250{\mu}m$, $50{\mu}m$ and there were significant difference in all the group. (P<0.05) (2) In type II gold, it was decreased in the sequence of $250{\mu}m$, $50{\mu}m$, $110{\mu}m$ and there were significant difference. (P<0.05) (3) In type IV gold, it was decreased in the sequence of $110{\mu}m$, $50{\mu}m$, $250{\mu}m$. There were significant difference between the group of $110{\mu}m$ and $50{\mu}m$, the group of $110{\mu}m$ and 250, but there were no significant difference in the group of $50{\mu}m$ and $250{\mu}m$. 3. The highest shear bond strength according to the size of sandblasting particle was $110{\mu}m$ in Ag-Pd alloy and type IV gold, $250{\mu}m$ in type II gold.

• Korean Journal of Agricultural and Forest Meteorology
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• v.18 no.4
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• pp.242-252
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• 2016

A process-based ecosystem model, BIOME-BGC, was applied to simulate seasonal and inter-annual dynamics of carbon and water processes for potential evergreen needleleaf forest (ENF) biome in Korea. Two simulation sites, Milyang and Unljin, were selected to reflect warm-and-dry and cool-and-wet climate regimes, where massive diebacks of pines including Pinus densiflora, P. koraiensis and P thunbergii, were observed in 2009 and 2014, respectively. Standard Precipitation Index (SPI) showed periodic drought occurrence at every 5 years or so for both sites. Since mid-2000s, droughts occurred with hotter climate condition. Among many model variables, Cpool (i.e., a temporary carbon pool reserving photosynthetic compounds before allocations for new tissue production) was identified as a useful proxy variable of tree carbon starvation caused by reduction of gross primary production (GPP) and/or increase of maintenance respiration (Rm). Temporal Cpool variation agreed well with timings of pine tree diebacks for both sites. Though water stress was important, winter- and spring-time warmer temperature also played critical roles in reduction of Cpool, especially for the cool-and-wet Uljin. Shallow soil depth intensified the drought effect, which was, however, marginal for soil depth shallower than 0.5 m. Our modeling analysis implicates seasonal drought and warmer climate can intensify vulnerability of ENF dieback in Korea, especially for shallower soils, in which multi-year continued stress is of concern more than short-term episodic stress.

• Journal of the Korean Data and Information Science Society
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• v.28 no.4
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• pp.853-862
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• 2017

In this study, we analyse the determinants of the youth employment rate of public agencies and local public enterprises. On the other hand the youth employment rate contains information of the youth employment rate and the size of the youth employment. We use pooled tobit model and panel tobit model since dependent variable is a censored form observed only in a certain area. The results of the analysis are summarized as follows. First, the panel tobit model is more statistically significant as compared to the combined tobit model. Second, the youth employment rate is more statistically significantly higher in 2014 and 2015 than in 2011. Third, the youth employment rate in public enterprises is more statistically significantly higher than that in local public agencies. Finally, the higher the average wage is, the lower the youth employment ratio is.

• Archives of Plastic Surgery
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• v.37 no.6
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• pp.721-725
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• 2010

Purpose: The survival of composite graft is dependent on three steps, (1) plasmatic imbibitions, (2) inosculation, and (3) neovascularization. Among the many trials to increase the survival rate of composite graft, prostaglandin E1 (PGE1) has beneficial effects on the microcirculatory level with vasodilating, antithrombotic, anti-inflammatory and neoangiogenic properties. Lipo-PGE1 which is lipid microspheres containing PGE1 had developed to compensate the systemic and local side effects of PGE1. This study was proposed to determine whether Lipo-PGE1 administration enhanced the survival of composite graft through neovascularization quantitatively in a rabbit ear model. Methods: Fourteen New Zealand White Rabbits each weighing 3~4 kg were divided in two groups: (1) intravenous Lipo-PGE1 injection group and (2) control group. A $2{\times}1\;cm$ sized, full-thickness rectangular composite graft was harvested in each auricle. Then, the graft was reaaproximated in situ using a 5-0 nylon suture. For the experimental group, $3{\mu}g$/kg/day of Lipo-PGE1 ($5{\mu}g$/mL) was administered intravenously through the marginal vein of the ear for 14 days. The control group was received no pharmacologic treatment. On the 14th postoperative day, composite graft of the ear was harvested and immunochemistry staining used Monoclonal mouse anti-CD 31 antibody was performed. Neoangiogenesis was quantified by counting the vessels that showed luminal structures surrounded by the brown color-stained epithelium and counted from 10 random high-power fields (400x) by independent blinded observer. Statistical analysis (Wilcoxon Signed Ranks test for nonparametric data) was performed using SPSS v12.0, with values of p<0.05 considered significant. Results: The mean number of the microvessels was $15.48{\pm}8.65$ in the experimental group and $9.82{\pm}7.25$ in the control group (p=0.028). Conclusion: The use of Lipo-PGE1 facilitated the neoangiogenesis, resulted in the improvement of the survival rate of graft. On the basis of this results, we could support wider application of Lipo-PGE1 for more effective therapeutic angiogenesis and successful survival in various cases of composite graft in the human.

• Journal of Korean Society of Transportation
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• v.33 no.6
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• pp.554-563
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• 2015

This study dealt with developing an accident model for rural signalized intersections with random parameter negative binomial method. The limitation of previous count models(especially, Poisson/Negative Binomial model) is not to explain the integrated variations in terms of time and the distinctive characters a specific point/segment has. This drawback of the traditional count models results in the underestimation of the standard error(t-value inflation) of the derived coefficient and finally affects the low-reliability of the whole model. To solve this problem, this study improves the limitation of traditional count models by suggesting the use of random parameter which takes account of heterogeneity of each point/segment. Through the analyses, it was found that the increase of traffic flow and pedestrian facilities on minor streets had positive effects on the increase of traffic accidents. Left turning lanes and median on major streets reduced the number of accidents. The analysis results show that the random parameter modeling is an effective method for investigating the influence on traffic accident from road geometries. However, this study could not analyze the effects of sequential changes of driving conditions including geometries and safety facilities.

• Journal of Preventive Medicine and Public Health
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• v.42 no.1
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• pp.12-20
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• 2009

Objectives : The purpose of this study was to analyze the association between the pattern of prophylactic antibiotic use(PAU) and the surgical site infection(SSI) rate for major surgeries in Korea. Methods : We retrospectively reviewed the medical records of patients who underwent cardiac, colon and gastric surgery, hysterectomies and hip/knee replacements at 20 hospitals, and inclusive of over 500 beds. We randomly sampled 60 cases per surgery type for patients discharged between September and November, 2006. A total fo 2,924 cases were included in our analysis. Cox's proportional hazard analysis was conducted to evaluate the association between the pattern of PAU and SSI rate. Results : The proportion of patients who received their first prophylactic antibiotics(PA) 1 hour before incision was 65.5%, who received inappropriate PAs was 80.8%, and the proportion of patients whose PA was discontinued within 24 hours of surgery was 0.5%. The average duration of PAU after surgery was 9 days. The relative risk(RR) of SSI in patients who received their first PA more than 1 hour before incision was significantly higher than for those who received it within 1 hour prior to incision(RR=8.20, 95% CI=4.81-13.99). Inappropriate PA selection increased SSI rate, albeit with marginal significance(RR=1.97, 95% CI=0.96-4.03). Also, prolonged PAU following surgery had no effect on SSI rate. Conclusions : These results suggest that the pattern of PAU in the surgeries examined was not appropriate. Errors in the timing of PAU and of PA selection increase SSI rate. SSI rate remained unaltered following prolonged PAU after surgery.