• 치과방사선
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• 제28권2호
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• pp.471-489
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• 1998

For the successful endodontic treatment, root canal should be cleaned thoroughly by accurate mechanical and chemical canal preparation and sealed completely with canal filling material without damaging the periapical tissues. The accuracy of the root canal length measurement is a prerequisite for the success of the endodontic treatment, and the root canal length is often determined by the standard periapical radiographs and digital tactile sense. In this study, the accuracy and the clinical usefulness of Digora/sup (R)/, an intraoral digital imaging processor and the conventional standard radiographs were compared by measuring the length from the top of the file to the root apex. 30 single rooted premolars were invested in a uniformly sized blocks and No.25 K-file was inserted into and fixed in each canal. Each block was placed in equal distance and position to satisfy the principle of the bisecting angle and paralleling techniques and Digora/sup (R)/ system's image and standard periapical radiographs were taken. Each radiograph was examined by 3 different observers by measuring the length from top of the file to the root apex and each data was compared and analyzed. The results were as follows; 1. In the bisecting angle technique, the average difference between the Digora/sup (R)/ system and standard periapical radiograph was 0.002 mm and the standard deviation was 0.341 mm which showed no statistically significant difference between the two systems(p>0.05). Also, in the paralleling technique, the average difference between these two system was 0.007 mm and the standard deviation was 0.323 mm which showed no statistically significant difference between the two systems(p>0.05). 2. In Digora/sup (R)/ system, the average difference between the bisecting angle and paralleling technique was -0.336 mm and the standard deviation was 0.472 mm which showed a statistically significant difference between the two techniques(p<0.05). Also, in the standard periapical radiographs, the average difference between the bisecting angle and paralleling technique was 0.328 mm and the standard deviation was 0.517 mm which showed a statistically significant difference between these two techniques(p<0.05). 3. In Digora/sup (R)/ system and the standard periapical radiographs. there was a statistically significant difference between the measurement using the bisecting angle technique and the actual length(p<0.05), But there was no statistically significant difference between the measurement using the paralleling technique and the actuallength(p>0.05). In conclusion. the determination of the root canal length by using the Digora/sup (R)/ system can give us as good an image as the standard periapical radiograph and using the paralleling technique instead of the bisecting angle technique can give a measurement closer to the actual canal length. thereby contributing to a successful result. Also. considering the advantages of the digital imaging processor such as decreasing the amount of exposure to the patient. immediate use of the image. magnification of image size. control of the contrast and brightness and the ability of storing the image can give us good reason to replace the standard periapical radiographs.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.351-355
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• 2003

Recently, the Rapid Prototyping System makes used of changing file format. The most problem is produced by this process. It is influenced by the precision of shape manufacturing. And It is most influenced by shrinkage rate within many elements influence the precision of 3D shape manufacturing. In result, the length strain in each axis cause at STL file transforming. It will compensate for utilizing the shrinkage rate.

• Restorative Dentistry and Endodontics
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• 제32권4호
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• pp.385-396
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• 2007

이 연구의 목적은 Mtwo 전동 파일의 사용에 있어서 제조사가 제안한 single length technique과 crown-down technique의 근관성형효율과 안전성을 비교하고 Mtwo 전동 파일의 변형된 사용방법을 제안하고자 하는 것이다. 기구의 종류와 사용방법에 따라 60개의 레진 블록 근관 모형 (Endo Training Bloc; Benstply Maillefer, Ballaigues, Switzerland)을 세 군으로 나누어 20개씩 표본을 성형하였다. MT군은 Mtwo 파일 (VDW, Munich, Germany)을 제조사의 추천방법인 single length technique으로, MC군은 Mtwo 파일을 crown-down technique으로 형성하였고, 대조군인 PT군은 ProTaper (Denstply Maillefer, Ballaigues, Switzerland)를 사용하였다. 모든 기구는 250 r.p.m., torque 2.2 N로 고정한 전동 모터 (X-smart; Denstply Maillefer, Ballaigues, Switzerland)로 사용하였다. 근관 성형 후, 스캐너로 근관 형성 전후의 이미지를 채득하여 중첩 비교함으로써 근단부로부터 1, 2, 3, 4, 5, 6, 7, 8 mm 높이에서의 중심변위율을 산출하였다. 순수 기구조작 시간 및 기구조작 동안의 binding빈도를 기록하였다. 근관 성형 후, 레진 블록의 무게 감소를 측정하였고 근관 성형에 사용된 파일의 파절이나 변형 및 근관 성형 후 형태의 이상을 조사하였다. 세 실험군의 측정 및 산출된 자료를 일원배치 분산분석 및 Duncan's Multiple Range Test로 사후 검정을 시행하여 비교하였으며, Fisher's exact test으로 근관의 이형성, 기구의 변형 그리고 기구 binding 등 발생 빈도를 유의 확률 95%에서 통계 검정하였다. 그 결과는 다음과 같다. 1. 근관의 만곡도 감소, 중심변위율, 레진 블록의 무게 감소, 기구 변형 등은 세 군간에 유의한 차이가 없었다 (p > 0.05). 2. 기구 조작 시간은 보면 MT군과 MC군이 PT군보다 짧았다 (p < 0.05). 3. Elbow는 MT군이 MC군에서 PT군보다 더 많이 형성되었다 (p < 0.05). Ledge는 세 군 모두에서 나타나지 않았다. 4. 파일 binding 횟수는 MC군이 가장 적고 PT군이 가장 많았다 (p < 0.05). 이상의 결과를 볼 때, Mtwo 전동 파일을 crown-down technique으로 사용하는 것이 single length technique과 유사한 성형 효율을 보이면서도 더 안전할 것으로 추정된다.

• Restorative Dentistry and Endodontics
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• 제35권6호
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• pp.453-460
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• 2010

연구목적: 치주질환이나 보철치료 계획으로 발치 예정인 성인 환자들을 대상으로 2 종의 전자근관장측정기를 사용하여 얻은 측정치의 정확성 (accuracy)을 평가하고, 현미경을 사용하여 각각 0.5 mark와 Apex mark 중에서 어느 지점에서 더 일관성 (consistency)을 보이는지를 비교하는 것이다. 연구 재료 및 방법: 치주 및 보철치료계획으로 인해 발거 예정인 26개의 건전한 치아들에서 13개는 Root ZX를 이용하여 측 정하였고, 나머지 13개는 i-ROOT를 이용하여 측정하였다. 국소마취를 시행 후 러버댐을 적용한 후 치아의 치수강을 개방하였다. 이때 교합면을 치아 장축에 수직으로 삭제함으로써 근관장을 측정할 때 발생할 수 있는 오차를 최소화하였다. 모든 근관에서 0.5 mark에서 먼저 근관장을 측정한 후 file을 더 전진하여 Apex mark에서 근관장을 다시 측정하였고, 이 지점에서 file을 Light cured glass ionomer로 고정하였다. 이후 치아들을 발거한 후 생리식염수에 보관하였다. 각각 치아들의 치근단부 5 mm를 21.3배율의 현미경 하에서 치근의 장축 방향으로 고속핸드피스 다이아몬드 바를 사용하여 조금씩 삭제하여 치질을 조심스럽게 제거하여 file tip을 완전히 노출시켰다. 현미경 하에서 진행한 과정들은 현미경과 연결된 DVD recorder를 통해 저장하였다. 이 이미지를 영상분석 프로그램인 i-solution에 적용하여 file tip에서부터 주근단공까지의 최단거리를 측정하였다. 결과: 1. Apex mark 이용 시 Root ZX와 i-ROOT 모두에서 주근단공 ${\pm}0.5\;mm$ 이내의 부위를 100% 찾아내는 정확도를 보였다. 2. 0.5 mark 이용 시 Root ZX에서는 100%, i-ROOT에서는 77%에서 주근단공 ${\pm}0.5\;mm$ 이내의 부위를 찾아내는 정확도를 보였다. 3. 표준편차와 사분위 값으로 평가하였을 때 Root ZX에서는 Apex mark가 0.5 mark보다 일관성을 나타냈으며 i-ROOT에서는 0.5 mark가 Apex mark보다 일관성을 보였으나 t-test 결과에서는 통계적 유의차가 없었다. 4. Apex mark와 0.5 mark 차이는 Root ZX에서는 0.22 mm, i-ROOT에서는 0.46 mm를 보였다. 결론: Apex mark와 0.5 mark 모두 일관성에 있어서의 차이는 없으나 Apex mark의 측정치가 0.5 mark에 비하면 주근단공에 거의 일치하는 점을 고려해, 임상에서 근관장을 결정할 시 Apex mark 측정치를 먼저 구한 후 기존연구들에서 보고된 주근단공에서부터 근관협착부까지의 평균거리인 0.5 mm를 빼는 것이 좋을 것으로 사료된다.

• Restorative Dentistry and Endodontics
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• 제37권2호
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• pp.79-83
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• 2012

Objectives: The purpose of this study was to evaluate the relation between intentionally induced internal stress and cyclic fatigue failure of .06 taper ProFile. Materials and Methods: Length 25 mm, .06 taper ProFile (Dentsply Maillefer), and size 20, 25, 30, 35 and 40 were used in this study. To give the internal stress, the rotary NiTi files were put into the .02 taper, Endo-Training-Bloc (Dentsply Maillefer) until auto-stop by torque controlled motor. Rotary NiTi files were grouped by the number of induced internal stress and randomly distributed among one control group and three experimental groups (n = 10, Stress 0 [control], Stress 1, Stress 2 and Stress 3). For cyclic fatigue measurement, time for separation of the rotary NiTi files was recorded. The fractured surfaces were observed by field emission scanning electron microscope (FE-SEM, SU-70, Hitachi). The time for separation was statistically analyzed using two-way ANOVA and post-hoc Scheffe test at 95% level. Results: In .06 taper ProFile size 20, 25, 30, 35 and 40, there were statistically significant difference on time for separation between control group and the other groups (p < 0.05). Conclusion: In the limitation of this study, cyclic fatigue failure of .06 taper ProFile is influenced by internal stress accumulated in the files.

• 대한치과보존학회:학술대회논문집
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• 대한치과보존학회 2003년도 제120회 추계학술대회 제 5차 한ㆍ일 치과보존학회 공동학술대회
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• pp.579-579
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• 2003

I. Objectives The aim of this study was to evaluate and compare the effectiveness of sealer placement in simulated root canal extensions using the K file, ultrasonic file, lentulo spiral and EZ-Fill. II. Materials and Methods Forty resin blocks were attained from cutting Endo-training Bloc with diamond saw. In each parallelepiped block, the simulated root canal was made with ＃20, 08taper GT file. After each block was longitudinally split into two halves using mallet and chisel, a standardized groove of 4mm in length, located 2mmapart from the root apex, was prepared on one wall of two halves using the custom-made knife to simulate the canal extensions with various irregularities.(omitted)

• Restorative Dentistry and Endodontics
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• 제37권4호
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• pp.220-227
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• 2012

Objectives: The study was to compare the shaping ability of Reciproc (VDW) and WaveOne (Dentsply Maillefer) instruments compared with ProTaper, Profile and hand instrument during the preparation of simulated root canals. Materials and Methods: Five groups (n = 5) were established. Reciproc, WaveOne, ProTaper, Profile and K file (K-flexo file) were used to prepare the resin simulated canals. A series of preoperative and postoperative images were taken by a microscope and superimposed in 2 different layers. The amount of resin removed from both the inner and the outer sides of the canal was measured to the level of 10 mm from the apical tip, with a 1 mm increment. Results: The mean of resin removal from the inner canal wall was not different from the outer canal wall for Reciproc and WaveOne groups at apical third (1 - 3 mm level). There was no difference in the change of working length and maintenance of canal curvature. NiTi instruments are superior to stainless-steel K file in their shaping ability. Conclusions: Within the limitation of this present study, Reciproc and WaveOne instruments maintained the original canal curvature in curved canals better than ProTaper and Profile, which tend to transport towards the outer canal wall of the curve in the apical part of the canal.

• Restorative Dentistry and Endodontics
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• 제41권4호
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• pp.304-309
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• 2016

Objectives: The purpose of this study was to compare the maximum screw-in forces generated during the movement of various Nickel-Titanium (NiTi) file systems. Materials and Methods: Forty simulated canals in resin blocks were randomly divided into 4 groups for the following instruments: Mtwo size 25/0.07 (MTW, VDW GmbH), Reciproc R25 (RPR, VDW GmbH), ProTaper Universal F2 (PTU, Dentsply Maillefer), and ProTaper Next X2 (PTN, Dentsply Maillefer, n = 10). All the artificial canals were prepared to obtain a standardized lumen by using ProTaper Universal F1. Screw-in forces were measured using a custom-made experimental device (AEndoS-k, DMJ system) during instrumentation with each NiTi file system using the designated movement. The rotation speed was set at 350 rpm with an automatic 4 mm pecking motion at a speed of 1 mm/sec. The pecking depth was increased by 1 mm for each pecking motion until the file reach the working length. Forces were recorded during file movement, and the maximum force was extracted from the data. Maximum screw-in forces were analyzed by one-way ANOVA and Tukey's post hoc comparison at a significance level of 95%. Results: Reciproc and ProTaper Universal files generated the highest maximum screw-in forces among all the instruments while M-two and ProTaper Next showed the lowest (p < 0.05). Conclusions: Geometrical differences rather than shaping motion and alloys may affect the screw-in force during canal instrumentation. To reduce screw-in forces, the use of NiTi files with smaller cross-sectional area for higher flexibility is recommended.

• Restorative Dentistry and Endodontics
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• 제39권4호
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• pp.270-275
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• 2014

Objectives: This study compared the mechanical properties of various instruments for canal exploration and glide-path preparations. Materials and Methods: The buckling resistance, bending stiffness, ultimate torsional strength, and fracture angle under torsional load were compared for C+ file (CP, Dentsply Maillefer), M access K-file (MA, Dentsply Maillefer), Mani K-file (MN, Mani), and NiTiFlex K-file (NT, Dentsply Maillefer). The files of ISO size #15 and a shaft length of 25 mm were selected. For measuring buckling resistance (n = 10), the files were loaded in the axial direction of the shaft, and the maximum load was measured during the files' deflection. The files (n = 10) were fixed at 3 mm from the tip and then bent $45^{\circ}$ with respect to their long axis, while the bending force was recorded by a load cell. For measuring the torsional properties, the files (n = 10) were also fixed at 3 mm, and clockwise rotations (2 rpm) were applied to the files in a straight state. The torsional load and the distortion angle were recorded until the files succumbed to the torque. Results: The CP was shown to require the highest load to buckle and bend the files, and the NT showed the least. While MA and MN showed similar buckling resistances, MN showed higher bending stiffness than MA. The NT had the lowest bending stiffness and ultimate torsional strength (p < 0.05). Conclusions: The tested instruments showed different mechanical properties depending on the evaluated parameters. CP and NT files were revealed to be the stiffest and the most flexible instruments, respectively.

• 수산해양기술연구
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• 제28권2호
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• pp.164-170
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• 1992

In order to understand and explain the spary combustion, it was necessary to understand the disintegration mechanisms of liquid jet. To understand the disintegration mechanisms of liquid jet, the disintegration phenomena and uniform droplet production regions of testing liquid jet was investigated by means of longitudinally vibration capillary nozzle, which was injected the testing liquids. The testing liquids were light oil and light oil and light oil blended with 25wt% fish oil (File fish oil, Sardine fish oil, Alaska pollac oil) The results can be summarized as follows: 1. The uniform droplet phenomena have been changed according to the frequency of capillary tube, the jet velocity and physical properties of testing oils. 2. Within the region of uniform droplet, Reynold number was increased as Weber number increases. 3. The lower limit of wave length in which uniform droplet was produced 0.8d which was lower than Rayleigh wave length 4. The light oil blended with file fish oil which has lower viscosity and surface tension had the widest uniform droplet production region on the frequency and velocity among testing oils. But light oil blended with sardine fish oil were similar with light oil in the uniform production region.