• Restorative Dentistry and Endodontics
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• 제43권3호
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• pp.33.1-33.8
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• 2018

Objectives: This study aimed to investigate the prevalence of a separate distolingual root and to measure the thickness of the buccal cortical bone in mandibular first molars in Koreans using cone-beam computed tomography (CBCT) images. Materials and Methods: High-quality CBCT data from 432 patients were analyzed in this study. The prevalence of a separate distolingual root of the mandibular first molar was investigated. The distance from the distobuccal and distolingual root apices to the outer surface of the buccal cortical bone was measured. We also evaluated the thickness of the buccal cortical bone. Results: The prevalence of a separate distolingual root (2 separate distal roots with 1 canal in each root; 2R2C) was 23.26%. In mandibular first molars with 2R2C, the distance from the distobuccal root apex to the outer surface of the buccal cortical bone was 5.51 mm. Furthermore, the distance from the distolingual root apex to the outer surface of the buccal cortical bone was 12.09 mm. In mandibular first molars with 2R2C morphology, the thickness of the buccal cortical bone at the distobuccal root apex of the mandibular first molar was 3.30 mm. The buccal cortical bone at the distobuccal root apex was significantly thicker in the right side (3.38 mm) than the left side (3.09 mm) (p < 0.05). Conclusions: A separate distolingual root is not rare in mandibular first molars in the Korean population. Anatomic and morphologic knowledge of the mandibular first molar can be useful in treatment planning, including surgical endodontic treatment.

• 대한치과보철학회지
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• 제33권1호
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• pp.130-143
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• 1995

The purpose of this study was to analyze the magnitude and distribution of stress using photoelastic model with the rigid connection using T-block attachment and non-rigid connection using key & keyway attachment. The vertical load of 16 Kg was applied on the central fossa of the tooth, the pontic and the implant, and the pattern and distribution under each condition was analyzed. The following results were obtained : 1. In case of vertical load on the central fossa of the implant, the stress was concentrated at the apex of the implant involving the mesial alveolar bone in both fixed partial denture with the rigid connection and that with the nonrigid connection and the stress concentration at the mesial cervical area of the implant was a little more in the nonrigid connection than in the rigid connection. 2. In case of vertical load on the central fossa of the pontic, the stress was concentrated at the apex of 2nd bicuspid in both 3 unit fixed partial denture with nonrigid connection and that with the rigid connection. The stress was more concentrated at the mesial alveolar bone of the implant, but the stress distribution at the natural teeth more favorable at the rigid connection than at the non-rigid connection in case of 4 unit fixed partial denture. 3. In case of vertical load of the central fossa of the 2nd bicuspid, much stress with 3 fringe order was observed at the apex of the 2nd bicuspid in the 3 unit fixed partial denture, but relatively even stress distribution was observed at the apex of the implant, the 1st and 2nd bicuspid, and the adjacent cuspid in the 4 unit fixed partial denture.

• Imaging Science in Dentistry
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• 제47권3호
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• pp.157-164
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• 2017

Purpose: This study determined and compared the distances from the maxillary root apices of posterior teeth to the floor of the maxillary sinus, or maxillary sinus distances(MSDs), and the distances from the mandibular root apices of the posterior teeth to the mandibular canal, or mandibular canal distances(MCDs), in Thai subjects with skeletal open bite and skeletal normal bite. Materials and Methods: Pretreatment cone-beam computed tomography (CBCT) images were obtained from 30 Thai orthodontic patients (15 patients with skeletal normal bite and 15 with skeletal open bite) whose ages ranged from 14 to 28 years. The CBCT images of the patients were processed and measured using the Romexis Viewer program. The MSDs and MCDs from the root apices of the maxillary and mandibular second premolar, first molar, and second molar to the maxillary sinus floor or the mandibular canal were measured perpendicularly to the occlusal plane. The Student t test was used for comparisons between the 2 groups. Results: The greatest mean MSDs were from the root apex of the second premolars in both groups, whereas the least mean MSDs were from the mesiobuccal root apex of the second molars. The greatest mean MCDs were from the mesial root apex of the first molars, whereas the least mean MCDs were from the distal root apex of the second molars. Conclusion: There were no differences in the mean MSDs or the mean MCDs between the skeletal normal bite group and the skeletal open bite group.

• 한국농공학회논문집
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• 제60권5호
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• pp.55-67
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• 2018

The objectives of this study were to monitor organic farming upland compared with conventional upland field and to evaluate nutrient loads reduction of surface cover effect with long-term historical climate data. APEX(Agricultural Policy Environmental eXtender) model was validated with experimental data and used for assessing surface cover scenarios for 30-year simulation periods. The validated values of RMSE(Root Mean Square Error), RMAE(Root Mean Absolute Error), $R^2$ and E(Nash-Sutcliffe efficiency) for runoff were 1.17-1.37 mm/day, 0.28-0.45 mm/day, 0.88-0.90 and 0.82-0.94 in two treatments, respectively. Those for water quality (nitrogen) were 0.05-0.16 kg/ha, 0.52-0.75 kg/ha, 0.67-0.72 and 0.32-0.70 in two treatments, respectively, and therefore the validated model showed good agreement with the observed runoff and nitrogen load for the study period. When decreasing the surface cover rate of organic farming field to 75%, 50%, 25%, and 0% (conventional field), average annual runoff increased by 7%, 15%, 23% and 31%, respectively. Under same condition of decreasing the surface cover rate, average annual nitrogen loads increased by 1.4 times, 1.7 times, 2.0 times, and 2.3 times compared with organic farming field, respectively. This study showed that it is possible to present an appropriate surface cover ratio to maintain conventional production and minimize nonpoint sources pollution for organic farming system, although long-term monitoring is needed to determine its effects on environmental concerns, crop competition, and other uncertainty.

• Restorative Dentistry and Endodontics
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• 제18권1호
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• pp.187-196
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• 1993

The purpose of this study was to evaluate the microleakage of retrofilled teeth with various materials [non-zinc Amalgam, IRM, Ketac-silver, CGP(cold-burnished, ultrafil)[and instruments for cavity preparation. Root apex were resected 2mm from apex horizontally and class I cavities were prepared in 2mm denpth, 1.5mm width and were filled with above mentioned materials. Root apex were resected 2mm from apex horizontally and class I cavities were prepared in 2mm depth, 1. 5mm width and were filled with above mentioned materials. 2% methylene blue dye solution was used for 4 days immersion and the linear leakage was measured with calipers and the volumetric leakage was determined with a spectrophotometer. The results were as follows : 1. Amalgam group showed the greatest amount of leakage and Ketac-silver group showed the least value. 2. By linear leakage test, the group retrofilled with Ketac-silver, or CGP showed better seal than the group of Amalgam or IRM. This was shown in both retrograde tip and Conventional method. 3. By volumetric leakage test, the group retrofilled with Ketac-silver showed significantly better seal than the group with IRM in retrograde tip method. 4. By volumetric leakage test, the group retrofilled with Ketac-silver showed significantly better seal than the group with Amalgam in the Conventional method.

• Restorative Dentistry and Endodontics
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• 제42권3호
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• pp.200-205
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• 2017

Objectives: The aim of this in vivo study was to assess the accuracy of 2 third-generation electronic apex locators (EALs), Propex II (Dentsply Maillefer) and Root ZX II (J. Morita), and radiographic technique for locating the major foramen (MF). Materials and Methods: Thirty-two premolars with single canals that required extraction were included. Following anesthesia, access, and initial canal preparation with size 10 and 15 K-flex files and SX and S1 rotary ProTaper files, the canals were irrigated with 2.5% sodium hypochlorite. The length of the root canal was verified 3 times for each tooth using the 2 apex locators and once using the radiographic technique. Teeth were extracted and the actual WL was determined using size 15 K-files under a ${\times}25$ magnification. The Biostat 4.0 program (AnalystSoft Inc.) was used for comparing the direct measurements with those obtained using radiographic technique and the apex locators. Pearson's correlation analysis and analysis of variance (ANOVA) were used for statistical analyses. Results: The measurements obtained using the visual method exhibited the strongest correlation with Root ZX II (r = 0.94), followed by Propex II (r = 0.90) and Ingle's technique (r = 0.81; p < 0.001). Descriptive statistics using ANOVA (Tukey's post hoc test) revealed significant differences between the radiographic measurements and both EALs measurements (p < 0.05). Conclusions: Both EALs presented similar accuracy that was higher than that of the radiographic measurements obtained with Ingle's technique. Our results suggest that the use of these EALs for MF location is more accurate than the use of radiographic measurements.

• Tribology and Lubricants
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• 제35권5호
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• pp.286-293
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• 2019

In friction and wear tests that use friction force microscopy (FFM), the wear debris transfer to the tip apex that changes tip radius is a crucial issue that influences the friction and wear performances of films and coatings with nanoscale thicknesses. In this study, FFM tests are performed for bilayer $MoS_2$ film to obtain a better understanding of how geometrical and chemical changes of tip apex influence the friction and wear properties of nanoscale molecular layers. The critical load can be estimated from the test results based on the clear distinction of the failure area. Scanning electron microscopy and energy-dispersive spectroscopy are employed to measure and observe the geometrical and chemical changes of the tip apex. Under normal loads lower than 1000 nN, the reuse of tips enhances the friction and wear performance at the tip-sample interface as the contact pair changes with the increase of tip radius. Therefore, the reduction of contact pressure due to the increase of tip radius by the transfer of $MoS_2$ or Mo-dominant wear debris and the change of contact pairs from diamond/$MoS_2$ to partial $MoS_2$ or Mo/$MoS_2$ can explain the critical load increase that results from tip reuse. We suggest that the wear debris transfer to the tip apex should be considered when used tips are repeatedly employed to identify the tribological properties of ultra-thin films using FFM.

• Clinics in Shoulder and Elbow
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• 제24권4호
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• pp.253-260
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• 2021

Background: To suggest a reasonable isometric point based on the anatomical consistency of interosseous membrane (IOM) attachment in association with topographic characteristics of the interosseous crests, the footprints of the central band (CB) of the IOM on the radial and ulnar interosseous crests (RIC and UIC) were measured. Methods: We measured the distance from the CB footprints from each apex of both interosseous crests in 14 cadavers and the angles between the forearm axis of rotation (AOR) and the distal slopes of the RIC and UIC in 33 volunteers. Results: The CB footprints lay on the downslope of both interosseous crests with its upper margin on average 3-mm proximal from the RIC's apex consistently in the radial length, showing normality (p>0.05), and on average 16-mm distal from the UIC's apex on the ulna without satisfying normality (p<0.05). The average angle between the UIC's distal slope and the AOR was 1.3°, and the RIC's distal slope to the AOR was 14.0°, satisfying the normality tests (p>0.05), and there was no side-to-side difference in both forearms (p<0.05). Conclusions: The CB attached to the downslope just distal to the RIC's apex constrains the radius to the UIC that coincides with the AOR of the forearm circumduction, maintaining itself both isometrically and isotonically.

• Imaging Science in Dentistry
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• 제52권2호
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• pp.197-207
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• 2022

Purpose: This study evaluated the associations of the dental arch form, age-sex groups, and sagittal root position (SRP) with alveolar bone thickness of the maxillary central incisors using cone-beam computed tomography (CBCT) images. Materials and Methods: CBCT images of 280 patients were categorized based on the dental arch form and age-sex groups. From these patients, 560 sagittal CBCT images of the maxillary central incisors were examined to measure the labial and palatal bone thickness at the apex level and the palatal bone at the mid-root level, according to the SRP classification. The chi-square test, Kruskal-Wallis test, and multiple linear regression were used for statistical analyses. Results: Significant differences were found in alveolar bone thickness depending on the arch form and SRP at the apex level. The square dental arch form and class I SRP showed the highest bone thickness at both levels of the palatal aspect. The taper dental arch form and class II SRP presented the highest bone thickness at the apex level of the labial aspect. No association was found between the dental arch form and SRP. Elderly women showed a significant association with thinner alveolar bone. Age-sex group, the dental arch form, and SRP had significant associations with alveolar bone thickness at the apex level. Conclusion: The patient's age-sex group, dental arch form, and SRP were associated with alveolar bone thickness around the maxillary central incisors with varying magnitudes. Therefore, clinicians should take these factors into account when planning immediate implant placement.

• 한국수자원학회:학술대회논문집
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• 한국수자원학회 2022년도 학술발표회
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• pp.82-82
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• 2022

최근 지구온난화로 인한 전 세계적 기후변화가 일어나고 있으며, 이러한 지구온난화 방지 대책으로 탄소의 중요성과 탄소중립을 선언하는 국가가 증가하고 있다. 탄소의 중요성이 증가함에 따라 유역 내의 탄소 중립이 중요 이슈로 떠오르고 있다. 유역 내 탄소 저장원으로는 숲, 하천, 토양 등이 존재하나 하천의 경우 탄소의 저장이 곧 수질 오염과 연결이 되기에 바람직한 방안이 될 수 없다. 그러나 토양의 경우 방대한 양의 탄소를 저장하기에 적합한 기능을 하기에 다른 저장원들에 비해 중요한 저장원으로 대두되고 있다. 토양탄소의 경우 일반적으로 유기물과 무기물의 형태로 토양에 저장된다. 이중 토양유기탄소는 장기간 토양 속에서 대기와의 탄소 조절 역할을 하기에 중요 요인으로 대두되고 있다. 하지만 기후변화로 인한 국지성 호우 및 무분별한 개발 등이 증가함에 따라 유역 내 토양 생태계의 변화가 일어나고 있으며, 이에 따른 유역 내 토양유기탄소 또한 손실이 일어나고 있다. 따라서 본 연구에서는 토양의 특성과 모델을 활용하여 유역단위 토양유기탄소량의 변화량을 산정하여 비교 및 분석을 하고자 한다. 이를 위해서 토양유기탄소의 모의가 가능한 APEX 모델을 활용하였으며, 선정된 연구 대상 지역의 토양 특성 자료를 활용하여 입력자료 전처리를 진행 후 모의를 진행하였다. 이후 선행연구 및 보고서를 통한 실측자료를 기반으로 모델 매개변수 보정을 진행하였으며, 보정된 결과를 통해 유역에 대한 토양유기탄소를 산정을 진행하였고 기간별 변화의 차이를 분석하였다. 해당 연구를 통해 유역 내 잠재되어있는 토양유기탄소량 정량화 등의 연구에 활용될 수 있을 것으로 기대한다.