• Journal of the Korea Convergence Society
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• v.10 no.3
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• pp.73-79
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• 2019

This study simulated external ear canal modeling with different external ear canal lengths, vertical flexion angles, and inner/outer diameter ratios using digital imaging and communications in medicine(DICOM) of the head temporal region and measured the acoustic sensitivity. The experiment was performed by increasing the audible frequency for humans by 200 Hz and expressing the frequency constantly transmitted at 1 Pa as the eardrum acoustic volume and presented the measurements by linear and quadratic curve regression analysis. The results showed that the longer the external ear canal length and the higher the ratio of the outer/inner diameter, the faster the acoustic response at lower frequencies. The acoustic sensitivity correlation of the meta-model using regression analysis showed a 77% influence by the external ear canal length and 5% by the external/internal diameter ratio, while the vertical flexion angle did not show a significant relationship. This showed that auditory acoustic sensitivity of humans is a factor that reacts faster at a low frequency when the external ear canal length is longer and when the difference between the outer and inner diameter is higher.

• Proceedings of the KOSOMBE Conference
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• v.1997 no.11
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• pp.399-402
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• 1997

It is important to find a accurate root canal length or successful endodontic therapy. By X-ray method takes a long time and difficult in a curved canal. After developed electronic apex locator has allowed to measure the root canal length with easy, in a short time also in a curved canal. But most electronic apex locators have the disadvantage which is too short reading or sometimes the measurement itself becomes impossible if there are electrolytes in the canal. To overcome this drawback, impedance ratio method has been developed. In this study, we have developed frequency dependent electronic apex locator to minimize the interference of electrolytes. And based on that also some error in clinic use, we added the other method. Difference of two signals which are used in calculation of impedance ratio was can be represent the status of root canal fluid. As a result, using impedance ratio method and auto-calibration by voltage difference method can reduce the measurement error.

• Anatomy and Cell Biology
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• v.56 no.1
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• pp.61-68
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• 2023

Anatomical knowledge of the occipital condyle (OC) and its relationships to surrounding structures is important for avoiding injury during craniovertebral junction (CVJ) surgeries. This study was conducted to evaluate the morphology and morphometry of OC and its relationship to foramen magnum, jugular foramen (JF), and hypoglossal canal (HC). Morphometric parameters including length, width, height, and distances from the OC to surrounding structures were measured. The oval-like condyle was the most common OC shape, representing for 33.0% of all samples. The mean length, width and height of OC were 21.3±2.4, 10.5±1.4, and 7.4±1.1 mm, respectively. Moreover, OC was classified into three types based on its length. The most common OC length in both sexes was moderate length or type II (62.5%). The mean distance between anterior tips and posterior tips of OC to basion, and opisthion were 11.5±1.4, 39.1±3.3, 25.2±2.2, and 27.4±2.7 mm, respectively. The location of intracranial orifice of HC was commonly found related to middle 1/3 of OC in 45.0%. JF was related to the anterior 2/3 of OC in 81.0%, the anterior 1/3 of OC in 12.5%, and the entire OC length in 6.5%. These morphological analysis and morphometric data should be taken into consideration before performing surgical operation to avoid CVJ instability and neurovascular structure injury.

• Restorative Dentistry and Endodontics
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• v.24 no.4
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• pp.633-638
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• 1999

The purpose of our study is to evaluate the ability of nickel-titanium(NiTi) files in maintaining the original curvature of a curved root canal during canal preparation. Curved canals on translucent resin blocks were prepared with Profiles and stainless steel files and they were placed at the platform which can reproduce the same position. The unprepared and prepared canal forms were accurately compared by double exposure technique of photography. The results were as follows : 1 NiTi files made a canal comparatively taper, but stainless steel files didn't make a canal taper, wicest at midportion and comparatively wide at a apical portion. 2. Canals preparations with no. 25 Profile.06 up to the working length were most excellent in taperness and in maintaining the original curvature. Canals prepared with no 30 Profile.06 up to the working length made a little outer transportation at a apical portion, but not severe. 3. Canal preparations with Profile GT were excellent in taperness and in maintaining the original curvature, but made more enlargement toward the inner side at the starting portion of the curvature. 4. Canal preparations with stainless steel files were not tapered and provided the largest transportation.

• Imaging Science in Dentistry
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• v.51 no.1
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• pp.17-25
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• 2021

Purpose: This study was performed to investigate mandibular canal displacement in patients with ameloblastoma using a 3-dimensional mirrored-model analysis. Materials and Methods: The sample consisted of computed tomographic scans of patients with ameloblastoma (n=10) and healthy controls (n=20). The amount of mandibular canal asymmetry was recorded as a continuous variable, while the buccolingual (yaw) and supero-inferior (pitch) directions of displacement were classified as categorical variables. The t-test for independent samples and the Fisher exact test were used to compare groups in terms of differences between sides and the presence of asymmetric inclinations, respectively (P<0.05). Results: The length of the mandibular canal was similar on both sides in both groups. The ameloblastoma group presented more lateral (2.40±4.16 mm) and inferior (-1.97±1.92 mm) positions of the mental foramen, and a more buccal (1.09±2.75 mm) position of the middle canal point on the lesion side. Displacement of the mandibular canal tended to be found in the anterior region in patients with ameloblastoma, occurring toward the buccal and inferior directions in 60% and 70% of ameloblastoma patients, respectively. Conclusion: Mandibular canal displacement due to ameloblastoma could be detected by this superimposed mirrored method, and displacement was more prevalent toward the inferior and buccal directions. This displacement affected the mental foramen position, but did not lead to a change in the length of the mandibular canal. The control group presented no mandibular canal displacement.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.21 no.2
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• pp.307-316
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• 1991

The purpose of this study is to improve the availabilities of radiographic technics as diagnostic method related to mandibular canal in dental clinic. For this study 12 dry mandibles were used and 12 orthopantomograms were taken for measuring the gonial angle and the angle of mandibular canal to inferior border of mandible. 12 sites located between the 1st premolar to the 3rd molar region of 3dry mandibles were selected randomly, for measuring the vertical image magnification rates on three films; intraoral film, orthopantomogram, and computed tomogram, respectively and the thickness of cortical bone, and for observing bucco-lingually and supero-inferiorly location of the mandibular canal. The acquired results were as follows: 1. The means of the gonial angle and the angle of mandibular canal to inferior border of mandible were 123.9° and 143.5° And the two angles of dry mandible in alveolar crest stage were greater than in alveolar socket stage. 2. The vertical image length on intraoral film by paralleling technic was magnified by 3.07% on the average, the length on orthopantomogram by 18.49%, and the length on computed tomogram by 0.27%. 3. Observation of the bucco-lingually positional relationship of the mandibular canal was impossible by occlusal projection with the cross section technic and intraoral standard projection with the Clack's rule, however, possible by computed tomogram. 4. The thickness of the cortical bone of mandible was thickest in inferior border, and thicker by 6.59% at buccal side than at lingual side.

• Imaging Science in Dentistry
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• v.39 no.2
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• pp.81-87
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• 2009

Purpose: To evaluate the anteroposterior length and buccal angle of the anterior loop, and the size and location of the mental foramen using cone beam computed tomography (CBCT). Materials and Methods: 100 CBCT images from 87 adults (43 males and 44 females) ranging in age from 20 to 73 years (average 50 years) with edentulous ridge of the mandibular premolar region were obtained. Axial, sagittal, coronal images were reconstructed from Dental and Block Images of CBCT. The anteroposterior length, shape and buccal angle of the anterior loop, and the size and location of the mental foramen were calculated from reconstructed images of axial, sagittal and coronal CBCT. Results: The anteroposterior length and buccal angle of the mental canal was 4.0${\pm}$1.2mm, 37.8${\pm}$11.60$^{\circ}$respectively. The loop type with straight course was the most common shape of the mental canal. The location of the mental foramen below the apex of the lower second premolar (78%) was the most common. The maximum size of the mental foramen was 4.6${\pm}$1.0 mm in width and 3.0${\pm}$0.6 mm in height. The inner size of the mental canal was 2.6${\pm}$0.6 mm in width and 2.1 mm${\pm}$0.4 mm in height. Conclusion: CBCT is useful to evaluate the anterior loop and mental foramen of the mandibular canal. Safe guideline of 4 mm from the most anterior point of the mental foramen is recommended for implant and surgical treatment. (Korean J Oral Maxillofac Radiol 2009; 39: 81-7)

• Journal of Ocean Engineering and Technology
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• v.12 no.1
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• pp.162-174
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• 1998

Construction of the Kyung-Inn Canal between Inchon and Han River water way of 18 kilometer length is considered recently. The canal may reduce traffic congestions between Seoul and Inchon, remarkably. Since the type of transportation system of the canal will be barge system, an analysis on the canal barge characteristics is carried out in this paper. The merits and demerits of various canal barge transportation systems are studied, respectively. Also, several barge connecting systems are studied and the corresponding characteristics are analyzed and compared. Optimal barge system is selected based on the simple modeling of the several barge systems and the relevant evaluations. Primitive design issue of the barge transportation system of the canal is also presented.

• Restorative Dentistry and Endodontics
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• v.23 no.1
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• pp.477-486
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• 1998

Recently the development of rotary instrument makes it possible that in root canal treatment operator saves much more time, maintans original curved canal shape and easily prepares continuous tapered root canal. The purpose of this experiment was to examine the smoothness of the internal surface of prepared root canal and the effectiveness of debridement in prepared root canal by SEM for the comparison of hand and Ni-Ti rotary instrument. 25 extracted human teeth were access opened and # 10 K-type file was introduced into canal until it was appeared at the apical foramen. The working length was established by subtracting 0.5mm from this measurement. Group 1. The root canal preparation was done to # 30 with working length and then step-back until # 45 with K-Flexofile (Maillefer, Swiss). Group 2. Root canal preparation was done by Naviflex Ni-Ti file (Brasseler, USA) as the same technique with group 1. Group 3. Canal was prepared by Profile .04 (Maillefer, Swiss) taper until #30. Group 4. With use of Quantec (Tycom, USA) root canal was prepared from file number 1 to 8. In group 1 and 2, the root canal irrigant was NaOCl and the other groups, NaOCl and RC-prep (Premine Dental Products, USA) was used. The prepared teeth were notched with high-speed bur as bucco-lingual direction and fractured with chisel and mallet, then examined with SEM. Group 1 showed smooth internal surface. There were scratches mainly to the axial direction. Group 2 showed similar characteristics to those in group 1. Group 3 showed more smoother and linear cutting surface with bised scratches. Group 4 has the almost same characteristics group 3 and there was no difference in the file design. Ni-Ti rotary root canal instrument prepare the dentinal wall more smoother than hand instrument. The effectiveness of debridement was not fully affected by file design. The isthmus area and accessory canals of the root canal system were not prepared in any group. According to the result, hand and rotary type instrumentation techniques were effective in removal of major amount of tissue from root canal but it was not complete. In the direction of cutting movement there was difference between them.

• Imaging Science in Dentistry
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• v.52 no.4
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• pp.359-364
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• 2022

Purpose: The aim of this study was to investigate the prevalence of infraorbital canal protrusion in an Egyptian subpopulation using cone-beam computed tomography and to describe its radiographic representation. Materials and Methods: This retrospective cross-sectional study was conducted using the records of 77 patients and 123 maxillary sinuses. The full lengths of the sinuses were visible for the detection of infraorbital canal protrusion. The infraorbital canals were classified into 3 types based on their relation to the sinus. If the septum was present, its length and its distance from the sinus floor were measured. Qualitative and quantitative variables were described as percentages and means with standard deviations, respectively. Results: The infraorbital canal most commonly presented as the normal confined type (detected in 78.1% of sinuses), whereas the suspended (or protruded) variant was found in 14.6% of the examined sinuses. The septal length ranged from 0.9 to 5.1 mm, with a mean of 2.8±1.1 mm. The distance to the sinus floor ranged from 5.2 to 29.6 mm depending on the sinus shape and size. Conclusion: The present study indicates that protrusion of the infraorbital canal is not rare, and surgeons that use the maxillary sinuses as corridors for their procedures must be more cautious, especially in the upper lateral confines of the sinus.