• Imaging Science in Dentistry
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• 제43권3호
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• pp.171-177
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• 2013

Purpose: The purpose of this study was to compare the efficacy of two imaging modes in a cone beam computed tomography (CBCT) system in detecting root fracture in endodontically-treated teeth with fiber posts or screw posts by selecting two fields of view. Materials and Methods: In this study, 78 endodontically-treated single canal premolars were included. A post space was created in all of them. Then the teeth were randomly set in one of 6 artificial dental arches. In 39 of the 78 teeth set in the 6 dental arches, a root fracture was intentionally created. Next, a fiber post and a screw post were cemented into 26 teeth having equal the root fractures. High resolution (HiRes) and standard zoom images were provided by a CBCT device. Upon considering the reconstructed images, two observers in agreement with each other confirmed the presence or absence of root fracture. A McNemar test was used for comparing the results of the two modes. Results: The frequency of making a correct diagnosis using the HiRes zoom imaging mode was 71.8% and in standard zoom was 59%. The overall sensitivity and specificity in diagnosing root fracture in the HiRes mode were 71.79% and 46.15% and in the standard zoom modes were 58.97% and 33.33%, respectively. Conclusion: There were no significant differences between the diagnostic values of the two imaging modes used in the diagnosis of root fracture or in the presence of root canal restorations. In both modes, the most true-positive results were reported in the post space group.

• 대한전자공학회논문지SD
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• 제46권3호
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• pp.20-25
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• 2009

본 논문에서는 모바일 환경 기반의 3차원 그래픽 연산을 위한 조명처리 엔진 및 쉐이더 프로세서에 사용 가능한 제곱근과 역제곱근 연산기의 구조를 제안한다. 제안하는 구조는 Taylor 전개식을 기반으로 하여 참조 테이블 및 보정 유닛으로 구성되어 있어 참조 테이블의 크기를 줄였다. 연산 결과는 IEEE-754 표준의 단정도 32 bit 부동소수점 형식과 모바일 환경을 위하여 이를 축소한 24 bit 부동소수점 형식에 대해 OpenGL 1.x ES 에서 요구하는 $10^{-5}$의 정확도를 거의 만족한다. 제안된 구조에 따라 설계된 제곱근 및 역제곱근 연산기는 Verilog-HDL을 사용하여 설계되었으며 파라미터 변경을 통하여 24 bit와 32 bit 연산이 가능하도록 합성이 가능하고 1사이클의 잠복기를 갖는다. 설계된 연산기들의 동작은 FPGA를 이용한 검증시스템을 통하여 검증하였다.

• Restorative Dentistry and Endodontics
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• 제43권1호
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• pp.11.1-11.10
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• 2018

Objectives: This study aimed to introduce the use of laser-induced breakdown spectroscopy (LIBS) for evaluation of the mineral content of root canal dentin, and to assess whether a correlation exists between LIBS and scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS) methods by comparing the effects of irrigation solutions on the mineral content change of root canal dentin. Materials and Methods: Forty teeth with a single root canal were decoronated and longitudinally sectioned to expose the canals. The root halves were divided into 4 groups (n = 10) according to the solution applied: group NaOCl, 5.25% sodium hypochlorite (NaOCl) for 1 hour; group EDTA, 17% ethylenediaminetetraacetic acid (EDTA) for 2 minutes; group NaOCl+EDTA, 5.25% NaOCl for 1 hour and 17% EDTA for 2 minutes; a control group. Each root half belonging to the same root was evaluated for mineral content with either LIBS or SEM/EDS methods. The data were analyzed statistically. Results: In groups NaOCl and NaOCl+EDTA, the calcium (Ca)/phosphorus (P) ratio decreased while the sodium (Na) level increased compared with the other groups (p < 0.05). The magnesium (Mg) level changes were not significant among the groups. A significant positive correlation was found between the results of LIBS and SEM/EDS analyses (r = 0.84, p < 0.001). Conclusions: Treatment with NaOCl for 1 hour altered the mineral content of dentin, while EDTA application for 2 minutes had no effect on the elemental composition. The LIBS method proved to be reliable while providing data for the elemental composition of root canal dentin.

• Journal of Periodontal and Implant Science
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• 제43권2호
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• pp.101-105
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• 2013

Purpose: The present study aimed to measure root surface roughness in teeth with periodontitis by a profilometer following root planning with ultrasonic and hand instruments with and without erbium-doped yttrium aluminium garnet (Er:YAG) laser irradiation. Methods: Sixty single-rooted maxillary and mandibular teeth, extracted because of periodontal disease, were collected. The crowns and apices of the roots were cut off using a diamond bur and water coolant. The specimens were mounted in an acrylic resin block such that a plain root surface was accessible. After primary evaluation and setting a baseline, the samples were divided into 4 groups. In group 1, the samples were root planned using a manual curette. The group 2 samples were prepared with an ultrasonic scaler. In group 3, after scaling with hand instrumentation, the roots were treated with a Smart 1240D plus Er:YAG laser and in group 4, the roots were prepared with ultrasonic scaler and subsequently treated with an Er:YAG laser. Root surface roughness was then measured by a profilometer (MahrSurf M300+RD18C system) under controlled laboratory conditions at a temperature of $25^{\circ}C$ and 41% humidity. The data were analyzed statistically using analysis of variance and a t-test (P<0.05). Results: Significant differences were detected in terms of surface roughness and surface distortion before and after treatment. The average reduction of the surface roughness after treatment in groups 1, 2, 3, and 4 was 1.89, 1.88, 1.40, and 1.52, respectively. These findings revealed no significant differences among the four groups. Conclusions: An Er:YAG laser as an adjunct to traditional scaling and root planning reduces root surface roughness. However, the surface ultrastructure is more irregular than when using conventional methods.

• Restorative Dentistry and Endodontics
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• 제45권3호
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• pp.34.1-34.7
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• 2020

Objectives: This study evaluated by using micro-computed tomography (micro-CT) the filling ability and sealer apical extrusion promoted by a new Sealer Injection System (SIS; Angelus) with side openings needle, in comparison with the conventional injection system, associated with a new ready-to-use calcium silicate-based sealer (Bio-C Sealer). Materials and Methods: Acrylic resin models containing a main curved artificial canal and 3 simulated lateral canals in apical, middle and cervical thirds were used. The main root canals were prepared using a rotary system up to size 35.05. The canals were filled with Bio-C sealer by using a single cone technique and the conventional delivery system or SIS. Samples were scanned in micro-CT. The percentage of voids throughout the entire extension of the main root canal and in each third of the lateral canals, besides the apical extrusion of the sealer was calculated. Data were submitted to t-test (p < 0.05). Results: There was no difference between both systems in the main root canals filling. Although the volume percentage of voids was similar in the apical and middle thirds of lateral canals, SIS had the greatest filling ability of the cervical third lateral canal. Moreover, the conventional system showed the highest apical extrusion of the sealer. Conclusions: The conventional and SIS obturation systems had an appropriate filling ability of the main root canal. SIS had the best filling of the cervical third of the lateral canals, besides lower sealer apical extrusion, suggesting its clinical indication.

• Restorative Dentistry and Endodontics
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• 제28권6호
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• pp.449-456
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• 2003

The purpose of this study is to evaluate the sealing effect of several root-end filling materials using spectrophotometric analysis. 180 single root teeth with one canal were instrumented and canal filled. Root resected and root end preparation was made. Teeth were randomly classified to S experimental group(MTA, EBA, IRM, TCP, ZOE) and 1 control group according to root-end filling material MTA group used PRO ROOT MT A, EBA group used Super EBA. TCP group used NEW APATITE LINER TYPE II main component of which is ${\alpha}-tricalcium$ phosphate (TCP). According to manufacture's instruction experimental material was mixed and retrfilled. After 2% methylene blue solution penetration absorbance for each test sample was measured with spectrophotometer (JASCO UV-530, Japan). The mean absorbance of control and experimental group was as follows; MTA: 0.092, IRM: 0.226, Super EBA: 0.255, ZOE: 0.374, Control: 0.425, TCP: 0.501 and the result analyzed by Turkey test at P=0.05 level. Conclusions of this study are as follows; 1. The absorbance increase in following sequence MTA, IRM, Super EBA, ZOE, Control. TCP. 2. MTA showed the least leakage but was not significant with IRM or Super EBA and was significant with control or TCP(p<0.05). 3. TCP had the most leakage and was not significant with control group.

• 대한소아치과학회지
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• 제43권2호
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• pp.129-136
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• 2016

본 연구의 목적은 근관 충전재로서 MTA(Endoseal, Endoseal MTA)의 밀폐 효과와 효율을 평가하는 것이다. 총 106개의 발거된 단근치가 사용되었으며, 충전된 실러에 따라 AH군(AH-26), PR군(ProRoot MTA), ES군(Endoseal), EM군(Endoseal MTA)으로 나누어졌고, 모든 충전시 소요 시간이 측정되었다. 그 군들은 다시 A 하위군, B 하위군으로 나누어 근관벽과의 밀폐성과 상아세관내 실러의 침투도를 각각 평가하였다. 결과는 근관 충전용 MTA는 AH-26에 비해 근관벽과의 밀폐성과 상아세관 침투도는 떨어졌으며, ProRoot MTA와 비교시 근관벽과의 밀폐성은 차이가 없었지만, 상아세관 침투도는 높았다. 작업 시간은 근관 충전용 MTA가 ProRoot MTA와 AH-26에 비해 짧았다. 결론적으로 근관 충전용 MTA는 레진계 실러보다 근관 밀폐 효과는 떨어지지만 MTA가 필요한 근관 충전시 효과적인 대안이 될 수 있다.

• ETRI Journal
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• 제30권6호
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• pp.774-782
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• 2008

An operational orbit determination (OD) and prediction system for the geostationary Communication, Ocean, and Meteorological Satellite (COMS) mission requires accurate satellite positioning knowledge to accomplish image navigation registration on the ground. Ranging and tracking data from a single ground station is used for COMS OD in normal operation. However, the orbital longitude of the COMS is so close to that of satellite tracking sites that geometric singularity affects observability. A method to solve the azimuth bias of a single station in singularity is to periodically apply an estimated azimuth bias using the ranging and tracking data of two stations. Velocity increments of a wheel off-loading maneuver which is performed twice a day are fixed by planned values without considering maneuver efficiency during OD. Using only single-station data with the correction of the azimuth bias, OD can achieve three-sigma position accuracy on the order of 1.5 km root-sum-square.

• 전기의세계
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• 제25권4호
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• pp.68-72
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• 1976

This study is initiated to solve the problem that the development of an electric machine to drive heavy horse-power load required in the rural district, where only single phase supply is available, is very urgent. As a method for this purpose, the single/three phase converter by single phase induction machine with a tapped auxiliary winding, running unloaded mechanically under single-phase source and supplying three-phase output to a loaded 3-phase induction motor, is devised and the pilot machine is put into test. Analysis based on hybrid equivalent circuit for the phase converter and symmertical component theory for the 3-phase load motor and practical experiment result in that optimum auxiliary winding ratio is to be 1.25 rather than theoretical .root.3/2 in order to keep the voltage unbalance ratio of 3-phase output from the converter as low as possible in both cases of starting and running the load motor.

• Imaging Science in Dentistry
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• 제43권2호
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• pp.123-128
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• 2013

Double tooth is a dental anomaly consequent to fusion of two or more teeth or gemination of a single tooth. This report describes a unique case of double tooth in relation to a mandibular lateral incisor exhibiting the presence of four root canals. The role of conventional radiography and advanced three-dimensional imaging techniques in the better assessment of complex root canal systems and their aid in endodontic management has also been highlighted.