• Restorative Dentistry and Endodontics
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• v.45 no.1
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• pp.7.1-7.9
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• 2020

Objectives: This study was performed to assess the anatomy of mandibular first molars. Materials and Methods: In this in vivo study, cone-beam computed tomography (CBCT) volumes of 312 bilateral intact first mandibular molars from 156 patients (79 men and 77 women; average age, 35.6 ± 11.2 years) were investigated in terms of the direction of each canal's curvature in the buccolingual and mesiodistal dimensions (direction of the position of the apex in relation to the longitudinal axis of the root), the presence of an isthmus (a narrow, ribbon-shaped communication between 2 root canals) in 3 segments (0-2, 2-4, and 4-6 mm) from the apex), and the presence and number of accessory canals (smaller canals besides the main root canals, connecting the pulp to the periodontium). Data were analyzed statistically (α = 0.05). Results: Mesiolingual canals were mostly buccally and distally inclined, while mesiobuccal and distolingual canals were mostly distally curved. Isthmuses were more common in younger patients (χ² test, p < 0.05). The average numbers of accessory canals in the apical, middle, and coronal segments were 9.9 ± 4.2, 6.9 ± 2.9, and 9.3 ± 3.0 canals per segment, respectively (analysis of variance, p < 0.001). Age and sex were not associated with the number of accessory canals (p > 0.05). Conclusions: The complex anatomy of these teeth deserves attention during non-surgical or surgical endodontic treatment. Around the apex, isthmuses might be more prevalent in younger and female individuals.

• Restorative Dentistry and Endodontics
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• v.14 no.1
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• pp.71-84
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• 1989

The purpose of this study was to evaluate the effect of tricalcium phosphate and Vitapex on the dogs' periapical tissues. Twenty mandibular premolars from 5 healthy dogs were used for this study. After the animals were anesthetized intramuscularly, pulp chambers were open and pulp tissue was extirpated with a barbed broach and H-file. Then the working length of the root canal was measured with H-file and pulp tissue was completely removed. Before the actual canal filling, the root canals of twenty teeth have been experimentally infected with opening the pulp chamber for 5 weeks. Periapical radiographs of the experimental teeth were taken to monitor the periapical pathological condition. Each root apex of 20 premolars was perforated with engine reamer and the root canals were enlarged with No. 30-60 H-files. They were divided into treated as follows. Control group: The root canal was filled with gutta-percha. Experimental group 1: The canal was dried with sterile paper points and mixture of tricalcium phosphate and physiological saline was overfilled beyond the root apex with a lentulo spiral. Then the root canal was filled gutta-percha and lateral condensation and the pulp chamber was filled with Caviton. Experimental group 2: The root canals were overfilled with Vitapex and were treated in the same manner as those in experimental group 1 At 1,2,3, and 8 weeks after experiment, the periapical tissues including the alveolar bone were fixed with 10% formalin solution for I week and decalcified with Plank-Rycho solution for 5 weeks. The specimens were embedded in paraffin and serial sections were cut into a thickness of 6 ${\mu}m$ at the plane of the root apex. Hematoxyline-eosin and Masson's trichrome stain were made for the histo-pathological examinations. The results were as follows: 1. Ingrowth of collagen fiber was observed from 1 week in control group and experimental groups. 2. The rate of bone formation of experimental group 1 was accelerated more than that of experimental group 2. 3. Resorption of cementum was seen in control group, but apposition of cementum was seen in experimental groups.

• Restorative Dentistry and Endodontics
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• v.29 no.4
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• pp.378-385
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• 2004

The purpose of this study was to compare the effects of preparation with GT files and profiles .04 in shaping of root canals and reconstruct the three-dimensional root canal system using micro computed tomography 40 canals of the extracted human mandibular molars were used, and randomly distributed into two experimental groups. In group 1. canals were prepared by GT files. In group 2, Profiles .04. were used. Apical preparation size was #30. For each tooth pre and post operative cross-sectional images were obtained by the micro CT at 50 micron intervals. Pre and post operative cross-sectional images of 1, 2, 3, 5, and 8mm from the apex were compared. For each section. canal area and centering ratio were determined. For each tooth pre- and post-operative root canal volume from the furcation to the apex of the roots was calculated by three-dimensional image software. Following results were obtained: 1. At 8mm from the apex, area of dentin removed by GT rotary file was significantly larger than that by Profile .04. And at the other levels there was not a significant difference. 2. There was a trend for GT rotary file to remain more centered in the canals than Profile .04 at all levels. But at 3mm level. there was a statistically significant difference. 3. In root canal volume increments after instrumentation, there was no significant difference between two groups.

• Restorative Dentistry and Endodontics
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• v.22 no.1
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• pp.347-357
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• 1997

An accurate working length is an essential factor in the success of endodontic treatment. There are several methods for determining working length; electronic apex locator, tactile sense by clinician, and radiography. Among these methods, the most commonly used method is radiography. But this method requires excessive radiation, long developing time, and many equipments. In additon, it could give an image distortion and two dimensional image. To improve these disadvantages, an intraoral digital radiographic system (Digora$^{(R)}$) which use an imaging plate instead of a film, was developed. The purpose of this investigation was to compare Digora imaging with conventional radiography in determining the working length. Maxillary first or second molars of human dried skull were used. Files were inserted into canals at randomly selected lengths, from 2mm short of the radiographic apex to 2rnm beyond. Radiographs and Digora images(Digora positive and Digora negative) were evaluated to determine the adjustment needed to place the file 0.5mm from the radiographic apex. The results were as follows ; 1. There was no significant difference in accuracy between those evaluated in ${\pm}0.5mm$ and those accurately evaluated in the 3 images. 2. When comparing the accuracy of each image without distinguishing the 3 images, in the group accurately determined within ${\pm}0.5mm$, the mesiobuccal group showed significantly higher accuracy compared to the palatal group(p<0.05).

• Korean Journal of Plant Taxonomy
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• v.47 no.4
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• pp.308-315
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• 2017

A new species, Corydalis bonghwaensis M. Kim & H. Jo, is described here. It is found on a mountain slope in Bongwha-gun, Gyeongsangbuk-do, Korea. Corydalis bonghwaensis shares several characteristics (white flowers, glabrous pedicels, white tubers, and the polygonal stigma) with related species C. namdoensis B. U. Oh & J. G. Kim and C. albipetala B. U. Oh. However, this new species has flowers which change from pale-yellow to white, a mucronated inner-petal apex, linear leaflets, and fusiform capsules with two-rowed seeds. In contrast, C. namdoensis has retuse inner-petal apex, various leaflets, and fusiform capsules with 2-rowed seeds. C. albipetala has retuse inner-petal apex, elliptical leaflets, and linear capsule with 1-rowed seeds. Also C. humilis B. U. Oh & Y. S. Kim has pale-blue purple flowers, elliptical leaflets, inflorescence with 1-5 flowers, and hemispherical lower-outer petal.

• Proceedings of the KOSOMBE Conference
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• v.1993 no.05
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• pp.57-60
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• 1993

A finite element-based computer simulation of excimer laser susery was conducted to study some factors on the surgery. In particular, the radius of curvature at the apex of the cornea was examined under various surgical conditions. Corneal tissue was assumed to be a nearly incompressible, linear elastic, homogeneous, isotropic material under very small deformation. The geometry of the human cornea was taken from the experimental data[1]. The simulation utilized ANSYS(Swanson Analysis System Inc.Rev.4.4A). In this study, the major factors which affect the outcomes of the excimer laser surgery were investigated. First, two patterns of surgery with various surgery thickness(40-70micrometers) were examind. The pattern#1 describes the meridian from the apex to the edge of the surgery area to be straight. And the corresponding meridian of the pattern 2 can be expressed as a quardratic function. The results show that the pattern #2 is more realistic and effective. Then, the effects of other factors were investigated based on the pattern #2. Other factors are:various diameters of the surgical area (3-8 milimeters), Young's modules(3.5-4.5MPa), and depth of surgery at the apex(40-70micrometers). Compared with the computer simulation of the radial keratotomy surgery[2], the excimer laser surgery was proven to be more effective in treating myopia patients. In conculusion, the results of the simulation are qualitative agreement with clinical experience[3] indicating the potential of the finite element model of the surgery as a guideline to the surgeon before actual surgery.

• Restorative Dentistry and Endodontics
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• v.10 no.1
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• pp.177-181
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• 1984

This study was to confirm the influence of intracanal instrumentation whether the pulp infection could be extended to periapical tissue. Fifty three teeth (24 badly decayed and infected, 29 sound teeth) were employed for this experiment and grouped as follows; 1. The specimen taken from the tip of 12 infected pulp in which reamer was inserted to the canal up to apical 1/3 and cultured as long as 48 hours. After 24 hours culture 11 cases were positive and 1 ease was negative but the time of incubation elapsed as 48 hours a negative case turned to positive. 2. Broth immersed paper disc was placed for 1 minute on the tip of 12 infected teeth with a reamer inserted to the apical end and cultured as usual manner in the incubator. At 24 hour culture the growth was significant in 9 cases and after 48 hours total 12 cases were positive. 3. Reamer was inserted to apical 1/3 on 14 sterile pulp canals and specimens obtained from the root tip were cultured for 24 and 48 hours. The results on both group were negative. 4. Similar maner with No.3 except reamer tip was rest exactly at the apex revealed only 2 cases of positive at 48 hour culture. 5. The tip of 24 reamers which reached to apical 1/3 and apex of infected canal were cultured for 24 and 48 hours. At 24 hour culture the growth was evident. 6. The tip of 14 reamers which inserted to apical 1/3 of sterile canal showed negative at 24 hour culture. The 15 cases of the tip which reached to the apex of sterile canal were found negative except 3 positive cases at 48 hour culture.

• Imaging Science in Dentistry
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• v.42 no.3
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• pp.129-137
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• 2012

Purpose: To compare different radiographic methods for assessing endodontically treated teeth. Materials and Methods: Root canal treatments were applied in 120 extracted mandibular teeth, which were divided into four groups: (1) ideal root canal treatment (60 teeth), (2) insufficient lateral condensation (20 teeth), (3) root canals filled short of the apex (20 teeth), (4) overfilled root canal treatment (20 teeth). The teeth were imaged using intraoral film, panoramic film, digital intraoral systems (CCD and PSP), CCD obtained with portable X-ray source, digital panoramic, and CBCT images obtained at 0.3 $mm^3$ and 0.2 $mm^3$ voxel size. Images were evaluated separately by three observers, twice. Kappa coefficients were calculated. The percentage of correct readings obtained from each modality was calculated and compared using a t-test (p<0.05). Results: The intra-observer kappa for each observer ranged between 0.327 and 0.849. The inter-observer kappa for each observer for both readings ranged between 0.312 and 0.749. For the ideal root canal treatment group, CBCT with 0.2 $mm^3$ voxel images revealed the best results. For insufficient lateral condensation, the best readings were found with periapical film followed by CCD and PSP. The assessment of teeth with root canals filled short of the apex showed the highest percentage of correct readings by CBCT and CCD. For the overfilled canal treatment group, PSP images and conventional periapical film radiographs had the best scores. Conclusion: CBCT was found to be successful in the assessment of teeth with ideal root canal treatment and teeth with canals filled short of the apex.

• Korean Journal of Optics and Photonics
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• v.16 no.2
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• pp.113-120
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• 2005

Luminous efficiency and uniformity in a LCD-BLU are mainly determined by fine scattering patterns formed on the light guide panel. We propose a novel fabrication method of 3-dimensional scattered patterns based on anisotropic etching of silicon wafers. Micro-pyramid patterns with 70.5 degree apex-angle and micro-prism patterns with 109.4 degree apex-angle can be self-constructed by the wet, anisotropic etching of (100) and (110) silicon wafers, respectively, and those patterns are easily duplicated by the PDMS replica process. Experimental results on spatial and angular distributions of irradiation from the light guide panel with the micro-pyramid patterns were very consistent with the calculation results. Surface roughness of the silicon-based micro-patterns is free from any artificial defects since the micro-patterns are inherently formed with silicon crystal surfaces. Therefore, we expect that the silicon based micro-patterning process makes it possible to fabricate perfect 3-dimensional micro-structures with crystal surface and apex angles, which may guarantee mass-reproduction of the light guide panels in LCD-BLU.

• Korean Journal of Acupuncture
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• v.27 no.2
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• pp.71-78
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• 2010

Objectives : The warm needling technique is a combination of acupuncture and moxibustion. The purpose of this study was to find the physical and thermal characteristics in order to identify the effects and mechanisms of the warm needling technique. Methods : In this study, the thermal changes were observed with a testo 845 device, which is an infra-red thermometer specifically designed for measuring a combustion of corn shaped moxibustion(moxa-corn). The thermal changes at the apex of the moxa-corn placed on the top of the an acupuncture were observed at the level of 1 cm and 2 cm from the apex to understand heat conduction through acupuncture needle for combustion of moxa-corn. Results and Conclusions : The thermal conduction through acupuncture needle from the moxa-corn was relative to the weight of moxa-corn and was inversely relative to the distance of the moxa-corn and acupuncture needle length. And the value of thermal conduction to the apex of the acupuncture needle from the moxa-corn was about $3{\sim}5^{\circ}C$. The above results suggest that the present study may be useful in finding the mechanism and effects of the warming needling technique.