• Imaging Science in Dentistry
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• v.32 no.3
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• pp.147-151
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• 2002

Purpose: To compare the standard deviation of gray levels on digital subtracted images obtained by different dental subtraction programs. Materials and Methods: Paired periapical films were taken at the lower premolar and molar areas of the phantoms involving human mandible. The bite registration group used Rinn XCP equipment and bite registration material, based on polyvinyl siloxane, for standardization. The no bite registration group used only Rinn XCP equipment. The periapical film images were digitized at 1200 dpi resolution and 256 gray levels by a flat bed scanner with transparency unit. Dental digital subtraction programs used for this study were Subtractor (Biomedisys Co., Korea) and Emago (Oral Diagnostic Systems, The Netherlands). To measure the similarities between the subtracted images, the standard deviations of the gray levels were obtained using a histogram of subtracted images, which were then analyzed statistically. Results: Subtracted images obtained by using the Emago program without manual selection of corresponding points showed the lowest standard deviation of gray levels (p<0.01). And the standard deviation of gray levels was lower in subtracted images in the group of a bite registration than in the group of no use of bite registration (p < 0.01). Conclusion: Digital radiographic subtraction without manual selection of reference points was found to be a convenient and superior method.

• Journal of dental hygiene science
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• v.11 no.3
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• pp.155-161
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• 2011

The purpose of this study was to obtain data necessary for guiding students in the future by grasping which rate of error is made how much depending on a shooting technique in the filming of periapical radiograph. 14,402 films, which were instructed targeting students for the Department of Dental Hygiene at D Health College and S Health College, were analyzed. The following results were obtained by conducting questionnaire survey targeting 263 students who completed the shooting practice lesson of bisecting angle technique and paralleling technique. 1. In case of having shot with bisecting angle technique, the ratio of error was the highest in both maxillary and mandibular first molar. 2. In case of having shot with paralleling technique, the ratio of error was the highest in the maxillary bicuspid and the mandibular first molar. 3. As for ratio of error in light of a shooting technique, both bisecting angle technique and paralleling technique were indicated to be the highest in inaccuracy of film position. The bisecting angle technique was indicated to have the higher ratio of error compared to the paralleling technique. 4. As for ratio of error in light of the processing technique, both bisecting angle technique and paralleling technique were indicated to be the highest in dark image and light image. The bisecting angle technique was indicated to have the higher ratio of error compared to the paralleling technique. 5. Students were indicated to feel it to be most difficult for grasping the processing level in the film-developing process. As the above results, to reduce ratio of error given the periapical radiography, a method of reducing ratio of error given the periapical radiography is considered to be what correctly understands the morphological and anatomical structure inside the mouth and what acquires the shooting technique by filming several times with having enough time.

• Journal of Periodontal and Implant Science
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• v.28 no.4
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• pp.797-809
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• 1998

The purposes of this study were to develop the computer program for the contrast and geometric correction in digital subtration radiography with the IDL (Interactive Data Language) and compare the results with this program for the correction of the non-standardized radiographs to those of standardized radiographs and those with "Emago" software, the commercial program for the correction. The procedures were written for the contrast correction and subtraction with the geometric correction, using IDL. 32 pairs of periapical radiographs of premolar and molar portion of two dry human mandibles were taken at two different occasions with XCP film holder(nonstandardized films) and another 32 pairs with customized XCP film holder(standardized films). Subtraction of standardized film pairs was performed. Subtraction after the contrast and geometric correction of non-standardized films was performed using the newly developed program and Emago software. Standard deviations of grey levels of the subtracted images by the newly developed program were compared with those of the standardized group and Emago-corrected group. Standard deviations of grey levels of new program-corrected group were much smaller than those of the Emago-corrected group (p<0.001) and slightly larger than those of standardized group (p<0.05). However, the difference was very minute. This study indicates that the newly developed program written with IDL may substitute the mechanical standardization for digital subtraction radiography.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.28 no.2
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• pp.387-413
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• 1998

Image resampling is of particular interest in digital radiology. When resampling an image to a new set of coordinate, there appears blocking artifacts and image changes. To enhance image quality, interpolation algorithms have been used. Resampling is used to increase the number of points in an image to improve its appearance for display. The process of interpolation is fitting a continuous function to the discrete points in the digital image. The purpose of this study was to determine the effects of the seven interpolation functions when image resampling in digital periapical images. The images were obtained by Digora, CDR and scanning of Ektaspeed plus periapical radiograms on the dry skull and human subject. The subjects were exposed to intraoral X-ray machine at 60kVp and 70 kVp with exposure time varying between 0.01 and 0.50 second. To determine which interpolation method would provide the better image, seven functions were compared; (1) nearest neighbor (2) linear (3) non-linear (4) facet model (5) cubic convolution (6) cubic spline (7) gray segment expansion. And resampled images were compared in terms of SNR(Signal to Noise Ratio) and MTF(Modulation Transfer Function) coefficient value. The obtained results were as follows ; 1. The highest SNR value(75.96dB) was obtained with cubic convolution method and the lowest SNR value(72.44dB) was obtained with facet model method among seven interpolation methods. 2. There were significant differences of SNR values among CDR, Digora and film scan(P<0.05). 3. There were significant differences of SNR values between 60kVp and 70kVp in seven interpolation methods. There were significant differences of SNR values between facet model method and those of the other methods at 60kVp(P<0.05), but there were not significant differences of SNR values among seven interpolation methods at 70kVp(P>0.05). 4. There were significant differences of MTF coefficient values between linear interpolation method and the other six interpolation methods (P< 0.05). 5. The speed of computation time was the fastest with nearest -neighbor method and the slowest with non-linear method. 6. The better image was obtained with cubic convolution, cubic spline and gray segment method in ROC analysis. 7. The better sharpness of edge was obtained with gray segment expansion method among seven interpolation methods.

• Imaging Science in Dentistry
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• v.34 no.3
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• pp.145-150
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• 2004

Purpose: To compare three digital radiographic imaging sensors by evaluating the visibility of endodontic file tips with interobserver reproducibility and assessing subjectively the clarity of images in comparison with the x-ray film images. Materials and Methods: Forty-five extracted sound premolars were used for this study. Fifteen plaster blocks were made with three premolars each and #8, 10, 15 K-flexofiles were inserted into the root canal of premolars. They were radiographically exposed using periapical x-ray films (Kodak Insight Dental film, Eastmann Kodak company, Rochester, USA), Digora imaging plates (Soredex-Orion Co., Helsinki, Finland), CDX 2000HQ sensors (Biomedisys Co., Seoul, Korea), and CDR sensors (Schick Inc., Long Island, USA). The visibility of endodontic files was evaluated with interobserver reproducibility, which was calculated as the standard deviations of X, Y coordinates of endodontic file tips measured on digital images by three oral and maxillofacial radiologists. The clarity of images was assessed subjectively using 3 grades, i.e. plus, equal, and minus in comparison with the conventional x-ray film images. Results: Interobserver reproducibility of endodontic file tips was the highest in CDR sensor (p < 0.05) only except at Y coordinates of #15 file. In the subjective assessment of the image clarity, the plus grade was the most frequent in CDR sensor at all size of endodontic file (p < 0.05). Conclusion : CDR sensor was the most superior to the other sensors, CDX 2000HQ sensor and Digora imaging plate in the evaluation of interobserver reproducibility of endodontic file tip and subjective assessment of image clarity.

• Journal of Korean Dental Science
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• v.4 no.1
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• pp.1-5
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• 2011

Purpose: Exact knowledge of the location and dimension of the pulp chamber help to maintain the pulp healthy during operative procedure and also reduces the risk of perforation of pulp chamber during root canal treatment. This in-vivo study was carried out to measure critical morphology of pulp chamber of mandibular molar using intra-oral periapical radiograph. Materials and Methods: Mandibular molar teeth of 56 patients were evaluated. The mandibular molar teeth whose pulp chamber was not violated by caries, restoration, fracture crown and those having closed apex were included in the study. The intraoral periapical radiographs were taken with paralleling angle technique using radio-opaque grid with 1 mm space. This grid was placed directly on the film. Results: In 94% of the mandibular first molars specimens the pulp chamber ceiling was at the level of the cemento-enamel junction. The measurements showing the lowest percentage variance were buccal cusp to furcation (approximately 11%) and buccal cusp to pulp chamber ceiling (approximately 15%). The distance from the cusp tip to pulp chamber ceiling height was approximately 6.0 mm, the distance from the pulpal floor to the furcation was approximately 3.0 mm, and the average height of a pulp chamber was 1.5 to 2.0 mm. Conclusion: The exact knowledge of distances of pulp chamber from various anatomical landmarks helps in proper assessment of root canals and ultimately avoids the failure of root canal treatment.

• Imaging Science in Dentistry
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• v.41 no.3
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• pp.115-121
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• 2011

Purpose : This article is to describe a modified device for intraoral radiography which was developed to obtain reproducible radiographic images for assessment of distal osseous defects of the mandibular second molar (2 Mm) after impacted third molar (3 Mm) surgery. Materials and Methods : A commercial available alignment system for posterior region was modified by adding a reference gauge pin (millimetric) and threading a hollow acrylic cylinder at the ring of the radiographic positioner to attach the X-ray collimator. The design included customized resin acrylic stent for the occlusal surface of the 2Mm in maximum intercuspal position, individualizing the biteblock positioner. Periapical radiographs were taken before and after surgical extraction of 3 Mm, employing the radiographic technique of parallelism described by Kugelberg (1986) with this modified film holder and inserting the gauge pin on the deepest bone probing depth point. Results : This technique permitted to obtain standardized periapical radiographs with a moderate to high resolution, repeatability, and accuracy. There was no difference between the measurements on the pre- and post-operative radiographs. This technique allowed better maintenance of the same geometric position compared with conventional one. The insertion of the gauge pin provided the same reference point and localized the deepest osseous defect on the two-dimensional radiographs. Conclusion : This technique allowed better reproducibility in posterior radiographic records (distal surface of 2 Mm) and more accurate measurements of radiographic bone level by the use of a millimetric pin.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.9 no.1
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• pp.7-12
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• 1979

The author had performed the measurement of the various teeth regions on 200 cases of Full-mouth roentgenogram taken with the measurable Grid to detect the degree of alveolar bone resorption, aged from 20 to 60 years of Korean, and to verify the effective result of measurable Grid as a new device which enables the observers to determine the correct length of images on the periapical standard film. The results were obtained as follows. 1. It was found that the degrees of alveolar bone resorption were different in the various teeth regions. 2. As a whole, alvolar bone resorption of anterior teeth regions was more severe than that of posterior teeth regions. 3. Alveolar bone resorption of mandibular region was more severe than that of maxillary region. 4. In sex difference, alveolar bone resorption of male is more severe than that of female, and it was increased with aging. 5. Measurable grid can be used as an adjunct of evaluation of alveolar bone resorption and of calculating the tooth length.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.23 no.2
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• pp.107-114
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• 2001

Objectives : To compare jaw bone density of young adults (control group) and post-menopausal women(experimental group) in periapical and panoramic film. Materials and Methods : The bone mineral density values of lumbar and femur were measured by dual-energy X-ray absorptiometry(DEXA) and T scores of lumbar were obtained. T scores were classified into 3 group (T<-2.5, $-2.5{\leqq}T<-1$, $-1{\leqq}T$). Radiographic densities of alveolar bones were measured from interdental bones of premolar, molar areas in the maxilla and mandible and expressed into copper step wedge thickness by Scion $Image^{(R)}$ program. We considered these values of step wedge thickness as bone density of alveolar bone. Panorama mandibular index(PMI) was calculated by the method that the height of the inferior cortex of the mandible was divided by the height from the lower border of the mandible to the superior edge of the mental foramen. Bone density of alveolar bone and PMI were analysed statistically. Results : There were significant differences in bone mineral density of lumbar and femoral neck between control and experimental groups. There were also significant differences in bone density of premolar and molar area of jaw between control and experimental groups by MANOVA test. When considered lumbar T variables, there was only difference in interdental bone density of maxillary molar area between control and experimental group, but there was interaction. Interdental bone density of experimental group was appeared higher in $-1{\leqq}T$ group and lower in T<-2.5 group than control group. There was significant difference in PMI between control and experimental groups, but there was also inter action, thus, PMI of experimental group was appeared higher in $-1{\leqq}T$ group and lower in T<-2.5 group than control group. Conclusion : There were significant differences of alveolar density and cortical bone thickness between young men and post-menopausal women in periapical and panoramic film. These differences were dependent on lumbar T.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.10 no.1
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• pp.63-68
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• 1980

The purpose of this article is to re-examine the roentgenographic appearance of alveolar osseous in an effort to determine the value of the orthopantomogram in the diagnosis of periodontal disease. A total of 158 osseous lesions from 13 human dry skulls were studied. 14 Ultra-speed periapical films, 2 bitewing films and Kodak panoramic film are used to obtain radiographs of all defects. The bisecting technic was used, with a target-film distance of. 8 inches and exposure factors of 70 kVp, 10MA and 0.4 sec. at anterior teeth, 0.6 see at posterior teeth in exposure time. For orthopantomogram, Panoura Eight-C was used with a exposure factors of 90kVp, 10MA. and 15sec. exposure time. All films were developed in a light. tight darkroom at 68°F for 4½ minutes. Comparison of orthopantomogram and intraoral films on the view-box was carefully studied in relation to the types of osseous defect visually evident; Proximal intraosseous defects, Interproximal craters, Interproximal hemisepta, Furcal defects on multirooted teeth, and Facial or Lingual one-walled defects. The results obtained were as follows; 1. Proximal osseous defects throughout the dental arches and furcal defects on facial and lingual surfaces of multirooted teeth can be identified with a high degree of accuracy from their orthopantomographic appearances. 2. Lesions on facial or lingual surface of the alveolar arches are rather difficult to locate or recognize on the dental radiographs. 3. In determining whether the proximal and furcal lesions are located facially or lingually, Orthopantomogram is superior to the conventional film Orthopantomogram obtained with standardization of head in proper position revealed the complete visualization of alveolar bone without showing occlusal surface of molars and proximal superimposition of teeth. Thus, on the standardized orthopantomograms, The roentgenographic characteristics of each defect were determined.