• Archives of Plastic Surgery
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• v.45 no.6
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• pp.572-577
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• 2018

Background Mandibular contouring surgery to produce a more slender and small face has become popular, especially in East Asia. Narrowing genioplasty should be simultaneously performed with mandibular angle resection to achieve satisfactory results. In Korea, T-genioplasty has been frequently performed for chin narrowing. The authors developed a new, safe, and reliable method, termed M-genioplasty, that can provide a more slender and attractive lower face. Methods From June 2013 to December 2017, 36 patients underwent M-genioplasty with mandibular angle resection for lower facial contouring. Horizontal and vertical osteotomies were performed obliquely. The resected bone segments were wedge-shaped. The remaining two bone segments were rotated and approximated centrally. The lateral mandible bony step-off was trimmed off for mandibular angle resection. Results In all patients, the facial contour sufficiently improved, and most patients were satisfied with the outcome. No severe complications took place during postoperative follow-up. Conclusions M-genioplasty can provide more mandibular angle resection and can create a more acute chin angle without bone resorption than other methods, including T-genioplasty. M-genioplasty with mandibular angle resection is a safer, more accurate, and more reliable method for lower facial contouring.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.24 no.1
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• pp.137-147
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• 1994

A digital imaging system using Machintosh Ⅱ ci computer, high resolution Sony XC-77 CCD camera, Quickcapture Frame Grabber Board was evaluated for quantitative analysis of standardized periapical film with aluminum step wedge. The results were as follows: 1. Correlation between Al thickness and gray level was high-positively associated(r²=0.99, p<0.001). 2. Correlation between measured weight of experimental lesion and estimated relative lesion volume by digital subtracted radiography was also high-positively associated (r²=0.98, p<0.001). 3. As exposure time was increased, mean gray level was decreased(p<0.01) and slope of regression line between Al thickness and gray level was also decreased (p<0.01). And when the exposure time was shorter than 0.2 second, the value of r² was relatively low. On the basis of the above results, it is considered that this digital imaging system using a Macintosh Ⅱ ci computer & a high resolution CCD monochrome camera will be useful in evaluating digitized image from standardized periapical film quantitatively.

• Imaging Science in Dentistry
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• v.51 no.3
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• pp.261-269
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• 2021

Purpose: The aim of this study was to evaluate the radiopacities of various types of restorative materials with different thicknesses compared with enamel, dentin, and aluminum. Materials and Methods: Four bulk-fill resins, 2 hybrid ceramics, 2 micro-hybrid resin composites, 6 glass ionomer-based materials, 2 zinc phosphate cements, and an amalgam were used in the study. Twelve disk-shaped specimens were prepared from each of 17 restorative materials with thicknesses of 1 mm, 2 mm, and 4 mm (n=4). All the restorative material specimens with the same thickness, an aluminum (Al) step wedge, and enamel and dentin specimens were positioned on a phosphor storage plate and exposed using a dental X-ray unit. The mean gray values were measured on digital images and converted to equivalent Al thicknesses. Statistical analyses were performed using 2-way analysis of variance and the Bonferroni post hoc test(P<0.05). Results: Radiopacity was significantly affected by both the thickness and the material type (P<0.05). GCP Glass Fill had the lowest radiopacity value for samples of 1 mm thickness, while Vita Enamic had the lowest radiopacity value for 2-mm-thick and 4-mm-thick samples. The materials with the highest radiopacity values after the amalgam were zinc phosphate cements. Conclusion: Significant differences were observed in the radiopacities of restorative materials with different thicknesses. Radiopacity was affected by both the material type and thickness.

• Imaging Science in Dentistry
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• v.37 no.4
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• pp.211-215
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• 2007

Purpose: The purpose of this study was to evaluate the effect of the kV on fractal dimension of trabecular bone in digital radiographs. Materials and Methods: 16 bone cores were obtained from patients who had taken partial resection of tibia due to accidents. Each bone core along with an aluminum step wedge was radiographed with an occlusal film at 0.08 sec and with the constant film-focus distance (32 cm). All radiographs were acquired at 60, 75, and 90 kV. A rectangular ROI was drawn at medial part, distal part, and the bone defect area of each bone core image according to each kV. The directional fractal dimension was measured using Fourier Transform spectrum, and the anisotropy was obtained using directional fractal dimension. The values were compared by the repeated measures ANOVA. Results : The fractal dimensions increased along with kV increase (p < 0.05). The anisotropy measurements did not show statistically significant difference according to kV change. The fractal dimensions of the bone defect areas of the bone cores have low values contrast to the non-defect areas of the bone cores. The anisotropy measurements of the bone defect areas were lower than those of the non-defect areas of the bone cores, but not statistically significant. Conclusion: Fractal analysis can notice a difference of a change of voltage of x-ray tube and bone defect or not. And anisotropy of a trabecular bone is coherent even with change of the voltage of x-ray tube or defecting off a part of bone.

• Imaging Science in Dentistry
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• v.35 no.1
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• pp.33-40
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• 2005

Purpose : (1) To analyse the effect of exposure time, ROI size and one impact factor in the image processing procedure on estimates of fractal dimension; and (2) to analyse the correlated relationship between the fractal dimension and the Cu-Eq value (bone density). Materials and Methods : The cylindric bone phantoms of 6 large and 5 small diameter having different bone densities respectively and human dry mandible segment with copper step wedge were radiographed at 1.0 and 1.2 sec esposure (70 kVp, 7 mA) using one occlusal film and digitized. Eleven rectangular ROIs from 11 cylindric bone phantoms and 4 rectan-gular ROIs from cortical, middle, periodontal regions, and socket of bone were selected. Gaussian blurred Image was subtracted from original image of each ROI and multiplied respectively by 1, 0.8, and 0.5, and then the image was made binary, eroded and dilated once, and skeletonized. The fractal dimension was calculated by means of a box counting method in the software ImageJ. Results : The fractal dimension was decreased gradually with continued bone density decrease showing strong correlations (bone phantom; r> 0.87, bone; r> 0.68) under 70 kVp 1.0 sec M = 0.8. Fractal dimensions showed the significant differerence (p < 0.05) between two different exposure times on the same small ROI of bone phantom. Fractal dimensions between two different sizes of ROI on bone phantom showed the significant differerence (p < 0.05) under 1.2 sec exposure, but did not show it (p > 0.05) under 1.0 sec exposure. Conclusions : Exposure time, ROI size, and modifying factor during subtracting could become impacting on the results of fractal dimension. Fractal analysis with thoroughly evaluated method considering the various impacting factors on the results could be useful in assessing the bone density in dental radiography.

• Imaging Science in Dentistry
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• v.43 no.3
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• pp.145-151
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• 2013

Purpose: This study was performed to evaluate and compare the radiopacity of dentin, enamel, and 8 restorative composites on conventional radiograph and digital images with different resolutions. Materials and Methods: Specimens were fabricated from 8 materials and human molars were longitudinally sectioned 1.0 mm thick to include both enamel and dentin. The specimens and tooth sections were imaged by conventional radiograph using #4 sized intraoral film and digital images were taken in high speed and high resolution modes using a phosphor storage plate. Densitometric evaluation of the enamel, dentin, restorative materials, a lead sheet, and an aluminum step wedge was performed on the radiographic images. For the evaluation, the Al equivalent (mm) for each material was calculated. The data were analyzed using one-way ANOVA and Tukey's test (p<0.05), considering the material factor and then the radiographic method factor, individually. Results: The high speed mode allowed the highest radiopacity, while the high resolution mode generated the lowest values. Furthermore, the high resolution mode was the most efficient method for radiographic differentiation between restorative composites and dentin. The conventional radiograph was the most effective in enabling differentiation between enamel and composites. The high speed mode was the least effective in enabling radiographic differentiation between the dental tissues and restorative composites. Conclusion: The high speed mode of digital imaging was not effective for differentiation between enamel and composites. This made it less effective than the high resolution mode and conventional radiographs. All of the composites evaluated showed radiopacity values that fit the ISO 4049 recommendations.

• The Journal of the Korea Contents Association
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• v.14 no.11
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• pp.355-361
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• 2014

The aim of the present study was to evaluate a relative emission of image plate (IP) in computed radiography (CR) system by using relative sensitivity in film/screen methods. The characteristic curve was obtained by using the uniform aluminum 11-step wedge penetrometer. X-ray exposure factors on radiographic digital image were 50 kVp, 10 mAs. We adjusted zero of all parameter of algorithms (MUSICA) so proximate to raw data and applied to 200 of exposure class. Modeling on relative emission of IP are used IP without fading time and IP after 4 hours, 8 hours, 12 hours, 24 hours in the respective storage after X-ray exposure. The results of this study showed that the sensitivity point density at the measuring of relative sensitivity in CR was suited pixel values of the 2000 easy to relatively measure the characteristic curve and when relative sensitivity is decreased, the amount of light emitted from the image signal for generating was also decreased. In conclusion, the proposed method of measurement of relative sensitivity can be utilized to evaluate the quantity of relative emission of IP in CR system.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.27 no.1
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• pp.73-86
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• 1997

This study was performed to assess the analyzing methods developed to detect clinically and quantitatively longitudinal bone changes. Through preliminary experiment, accuracy of Cu-Eq value conversion to the mass of HA was examined. For main experiment, 15 intraoral radiograms taken at soon, 1st, 2nd, 4th, and 6th week after implantation of mixture in extracted sites of 3 cases were used. We took the radiograms with copper step wedge as test object and HA phantom X -ray taking was standardized by using Rinn XCP device customized directly to the individual dentition with resin bite block. The images inputted by Quick scanner into computer were digitized and analyzed by NIH image program. The stability of the copper equivalent transformation and the usefulness of two analyzing methods by ROI and Reslice were examined. Obtained results as follows: 1) On the Cu equivalent images, the coefficient of variation in the measurement of Cu-Eq. value of ROI ranged from 0.05 to 0.24 and showed high reproducibility. 2) All results obtained by resliced contiguous image were coincident with those obtained from the assessment by ROI and formation of plot profile. 3) On the stacked and resliced image at the line of interest, we could analyze directly and quantitatively the longitudinal changes at several portions by plot profile and qualitatively by surface plot. 4) Implant area showed marked resorption till 2 weeks after implantation and showed significant increase in Cu-Eq. value at 6th week(p<0.01) and periapical area showed increase in Cu-Eq. value at 6th week compared to after-operation's.

• Imaging Science in Dentistry
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• v.30 no.4
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• pp.243-248
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• 2000

Purpose: The aim of this study was to determine the relative radiopacities of cavity lining materials (Resin-modified Glass Ionomer cement, Compomer and Plowable resin) for posterior composite resin restoration. Material & Methods: Resin-modified glass ionomer cement (Fuji II LC, Vitrebond/sup TM/), Compomers (Dyract /sup (R)/ Compoglass, F2,000, Dyract/sup (R)/ flow Compoglass Flow) and Flowable resins (Tetric/sup (R)/ flow, Aeliteflo/sup TM/ Revolution/sup TM/) were used. Five specimens of 5 mm in diameter and 2 mm thick were fabricated with each material. Human molars were horizontally sectioned 2 mm thick to include both enamel and dentin. The radiopacities of enamel, dentin, cavity lining materials, aluminum step wedge were obtainded from conventional radiograph and NIH image program. Results: All the tested lining materials showed levels of radiopacity the same as or greater than that of dentin. All compomer tested (Dyract, Compoglass, F2,000, Dyract flow, Compoglass Flow) and Vitrebond/sup TM/, Tetric/sup (R)/ flow were more radiopaque than enamel. The radiopacities of Fuji II LC and Revolution/sup TM/ were between enamel and dentin and resin-modified glass ionomer cement, Compomer and Tetric/sup (R)/ flow were greater than those of Revolution/sup TM/, Aeliteflo/sup TM/ or dentin. The level of radiopacity of the tested materials was variable; those with low radiopacity should be avoided in class II restorations, where a clear determination of recurrent caries by the examining clinician could be compromised. Conclusion: Clinician should be able to distinguish these cavity lining materials radiographically from recurrent decay, voids, gaps, or other defects that lead to clinical failure. Utilization of materials ranked more radiopaque than enamel would enable clinicians to distinguish the lining material from tooth structure.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.24 no.5
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• pp.577-588
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• 2011

This paper provides a novel extended Moving Least Squares(MLS) difference method for the potential problem with weak and strong discontinuities. The conventional MLS difference method is enhanced with jump functions such as step function, wedge function and scissors function to model discontinuities in the solution and the derivative fields. When discretizing the governing equations, additional unknowns are not yielded because the jump functions are decided from the known interface condition. The Poisson type PDE's are discretized by the difference equations constructed on nodes. The system of equations built up by assembling the difference equations are directly solved, which is very efficient. Numerical examples show the excellence of the proposed numerical method. The method is expected to be applied to various discontinuity related problems such as crack problem, moving boundary problem and interaction problems.