Effective dose from direct and indirect digital panoramic units

PURPOSE: This study aimed to provide comparative measurements of the effective dose from direct and indirect digital panoramic units according to phantoms and exposure parameters. MATERIALS AND METHODS: Dose measurements were carried out using a head phantom representing an average man (175 cm tall, 73.5 kg male) and a limbless whole body phantom representing an average woman (155 cm tall, 50 kg female). Lithium fluoride thermoluminescent dosimeter (TLD) chips were used for the dosimeter. Two direct and 2 indirect digital panoramic units were evaluated in this study. Effective doses were derived using 2007 International Commission on Radiological Protection (ICRP) recommendations. RESULTS: The effective doses of the 4 digital panoramic units ranged between 8.9 microSv and 37.8 microSv. By using the head phantom, the effective doses from the direct digital panoramic units (37.8 microSv, 27.6 microSv) were higher than those from the indirect units (8.9 microSv, 15.9 microSv). The same panoramic unit showed the difference in effective doses according to the gender of the phantom, numbers and locations of TLDs, and kVp. CONCLUSION: To reasonably assess the radiation risk from various dental radiographic units, the effective doses should be obtained with the same numbers and locations of TLDs, and with standard hospital exposure. After that, it is necessary to survey the effective doses from various dental radiographic units according to the gender with the corresponding phantom.

A repeatedly recurrent desmoplastic ameloblastoma after removal and allobone graft: Radiographic features compared with histological changes

A 40-year-old man suffered from a repeatedly recurrent desmoplastic ameloblastoma in the right maxillary anterior and premolar regions. During the first visit, the patient was provisionally histopathologically diagnosed with a developmental cyst, and it was confirmed to be unicystic ameloblastoma and resected. Four years later, the lesion recurred, and was diagnosed as a desmoplastic type of ameloblastoma and removed again. Then, 5 years after the second surgery, the lesion recurred again, and was diagnosed as a type containing a follicular pattern, recurrent ameloblastoma. A panoramic radiograph showed a multilocular and mixed radiolucent/radiopaque expansile lesion at the first visit, a unilocular cystic lesion confined to the premolar area at the second visit, and a small soap bubble appearance in the molar area in the final visit. Cone-beam computed tomographic images of the final recurrence of the tumor revealed multiple small cyst-like structures in the right maxillary anterior and posterior regions.

Bone density around the fixture after function of implant molar prosthesis using CBCT / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to examine the significance of increased bone density according to whether bone grafts were applied using demographic data with Cone Beam Computed Tomography (CBCT) and to compare the bone densities between before and after implant prosthesis using the Hounsfield index. MATERIALS AND METHODS: Thirty-six randomly selected computed tomography (CT) scans were used for the analysis. The same sites were evaluated digitally using the Hounsfield scale with V-Implant 2.0(TM), and the results were compared with maxillary posterior bone graft. Statistical data analysis was carried out to determine the correlation between the recorded Hounsfield unit (HU) of the bone graft and implant prosthesis using a Mann-Whitney U test and Wilcoxon Matched-pairs test. RESULTS: The bone grafted maxillary posterior teeth showed an increase in the mean values from-157 HU to 387 HU, whereas non-grafted maxillary posterior teeth showed an increase from 62 HU to 342 HU. After implantation, the grafted and non-grafted groups showed significantly higher bone density than before implantation. However, the grafted group showed significantly more changes than the non-grafted group. CONCLUSION: Bone density measurements using CBCT might provide an objective assessment of the bone quality as well as the correlation between bone density (Hounsfield scale) and bone grafts in the maxillary molar area.

Absorbed and effective dose in direct and indirect digital panoramic radiography / 대한구강악안면방사선학회지

PURPOSE: We evaluated the absorbed doses to the organs and calculated the effective doses when using the digital panoramic radiography. MATERIALS AND METHODS: The absorbed dose averages in major organs of oral and maxillofacial region were measured using the Dental head phantom (CIRS Co., USA), (n)Li(2)B(4)O(7) TLD chip and UD-716AGL dosimeter (Matsushita Electric Industrial Co., JPN) when performing indirect and direct digital panoramic radiography. Effective doses were calculated from correspond to ICRP 2007 recommendations for two panoramic radiography. RESULTS: The absorbed dose average on indirect and direct digital panoramic radiography was highest in parotid glands as measured 1259.6 mGy and 680.7 mGy respectively. Absorbed dose average in another organs were high in order of esophagus, submandibular gland, tongue and thyroid gland on both types of digital panoramic radiography. The absorbed dose average was higher on indirect type than direct one (p<0.05). The effective dose was higher on indirect type than direct one as measured 13.28 mSv and 8.70 mSv respectively. CONCLUSION: The absorbed doses in salivary gland and oral mucosa were high. However, thyroid gland also demands the attention on radiography due to high tissue weighting factor in spite of the low absorbed dose.

Synovial chondromatosis and osteochondroma in TMJ with CBCT images / 대한구강악안면방사선학회지

Synovial chondromatosis is an uncommon disorder characterized by metaplastic formation of multiple cartilaginous and osteocartilaginous nodules within connective tissue of the synovial membrane of joints. Osteochondroma is a benign lesion of osseous and cartilagenous origin. It is frequently found in the general skeleton, but is rare in the mandibular condyle. We experienced 2 patients with abnormal appearance of temporomandibular joint. Histologic diagnoses were not obtained, because surgery was unwarranted in view of the lack of symptoms and the benign differential diagnosis. We describes 2 cases that show the characteristics of both disease simultaneously.

Buccal cortical bone thickness on CBCT for mini-implant / 대한구강악안면방사선학회지

PURPOSE: Cortical bone thickness is one of the important factor in mini-implant stability. This study was performed to investigate the buccal cortical bone thickness at every interdental area as an aid in planning mini-implant placement. MATERIALS AND METHODS: Two-dimensional slices at every interdental area were selected from the cone-beam computed tomography scans of 20 patients in third decade. Buccal cortical bone thickness was measured at 2, 4, and 6 mm levels from the alveolar crest in the interdental bones of posterior regions of both jaws using the plot profile function of Ez3D2009trade mark (Vatech, Yongin, Korea). The results were analyzed using by Mann-Whitney test. RESULTS: Buccal cortical bone was thicker in the mandible than in the maxilla. The thickness increased with further distance from the alveolar crest in the maxilla and with coming from the posterior to anterior region in the mandible (p<0.01). The maximum CT value showed an increasing tendency with further distance from the alveolar crest and with coming from posterior to anterior region in both jaws. CONCLUSION: Interdental buccal cortical bone thickness varied in both jaws, however our study showed a distinct tendency. We expect that these results could be helpful for the selection and preparation of mini-implant sites.

Measurement of hard tissue density of head phantom based on the HU by using CBCT / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to determine a conversion coefficient for Hounsfield Units(HU) to material density (g cm-3) obtained from cone-beam computed tomography (CBMercuRay(TM)) data and to measure the hard tissue density based on the Hounsfield scale on dental head phantom. MATERIALS AND METHODS: CT Scanner Phantom (AAPM) equipped with CT Number Insert consists of five cylindrical pins of materials with different densities and teflon ring was scanned by using the CBMercuRay(TM)(Hitachi, Tokyo, Japan) volume scanner. The raw data were converted into DICOM format and the HU of different areas of CT number insert measured by using CBWorks(TM). Linear regression analysis and Student t-test were performed statistically. RESULTS: There was no significant difference (P>0.54) between real densities and measured densities. A linear regression was performed using the density, rho (g cm-3), as the dependent variable in terms of the HU(H). The regression equation obtained was rho=0.00072H-0.01588 with an R(2) value of 0.9968. Density values based on the Hounsfield scale was 1697.1+/-24.9 HU in cortical bone, 526.5+/-44.4 HU in trabecular bone, 2639.1+/-48.7 HU in enamel, 1246.1+/-39.4 HU in dentin of dental head phantom. CONCLUSION: CBCT provides an effective option for determination of material density expressed as Hounsfield Units.

Quantitative assessment of periimplant bone density (HU) on CBCT image / 대한구강악안면방사선학회지

PURPOSE: The primary aims of this retrospective study were to compare subjective bone quality and bone quality based on the Hounsfield scale in different segments of the edentulous jaw, and to establish quantitative and objective assessment of the bone quality. MATERIALS AND METHODS: Twenty eight randomly selected cone-beam computed tomographic (CBCT) scans were analyzed. For evaluation one hundred and twelve edentulous areas were selected. Implant recipient sites were evaluated visually for Lekholm and Zarb classification. The same sites were subsequently evaluated digitally using the Hounsfield scale with Vimplant2.0(TM), and the results were correlated with visual classification. Data was subject for statistical analysis in order to determine correlation between recorded HU and the regions of the mouth with the Kruskal-Wallis test. RESULTS: The highest unit/mean density value (311 HU) was found in the anterior mandible, followed by 259 HU for the posterior mandible, 216 HU for the anterior maxilla, and 127 HU for the posterior maxilla. These results demonstrate a strong correlation for HU depending on the region of the mouth (p<0.001). The relationship between HU and type 4 bone was found to be significant (r=0.74). CONCLUSION: Knowledge of the Hounsfield value as a quantitative measurement of bone density can be helpful as a diagnostic tool by using CBMercuRay(TM) with Vimplant(TM) software.

Comparison of the buccolingual inclination in alveolar bone and tooth using dental CBCT / 대한구강악안면방사선학회지

PURPOSE: It is important to determine the bucco-lingual inclination of implants on radiographs before the implant surgery. The purpose of this study was to compare the buccolingual inclination in alveolar bone and the tooth with dental cone beam CT and to prepare the standard for the buccolingual inclination of implant. MATERIALS AND METHODS: Axial, panoramic, and buccolingually sectioned images of 80 implant cases with stent including straight marker using CB Mercuray(TM) (Hitachi, Japan) were evaluated. The comparison of the buccolingual inclination of remained alveolar bone with the tooth and the marker on buccolingually sectioned views was performed statistically. RESULTS: The average buccolingual inclination of remained alveolar bone and tooth was 82.8+/-4.6degrees and 85.8+/-4.7degrees (p0.05, r=0.12) at the 2nd premolar area in upper jaw. The average buccolingual inclination of remained alveolar bone and tooth was 81.3+/-8.3degrees and 87.5+/-6.3degrees (p>0.05, r=0.85) at the lower 2nd premolar area and 94.3+/-6.6degrees and 93.3+/-7.2degrees respectively (p>0.05, r=0.91) at the 1st molar area in lower jaw. The inclinations of markers were very different from those of remained bone at the most of areas except the upper 2nd premolar area (r=0.79). CONCLUSION: We recommend dental CBCT analysis for determining the buccolingual inclination of dental implant, because of significant difference, in average, between the buccolingual inclination of remained alveolar bone and tooth.

Positional change of the condylar heads after wearing complete denture on dental cone beam CT / 대한구강악안면방사선학회지

PURPOSE: The aim of this study was to evaluate the change in the position of the mandibular condyle within articular fossa by a CBCT after wearing complete denture (CD). MATERIALS AND METHODS: CBCT of 34 temporomandibular joints were taken from 9 male and 8 female patients with CB Mercuray(TM) (Hitachi, Japan) before and after wearing a CD for rehabilitation. Position of mandibular condyle within articular fossa at centric occlusion was evaluated with Vimplant2.0(TM) (CyberMed, Korea) on the central parasagittal view and curved panoramic coronal view of the condylar head. A statistical evaluation was done with SPSS. RESULTS: The range of anteroposterior positional rate (AP) of condylar head within articular fossa was -16-5 and -10-12 respectively on the right and left sides. Before wearing CD, the AP rate showed discrepancy between right and left sides (p<0.05). After wearing CD, both condyles showed a tendency to decrease in posterior condylar position (right side; p<0.05). The average discrepancy between right and left side in mediolateral positional rate (MD) was 15.5 and 4.5 respectively before and after wearing CD. The improvement was observed in mediolateral relationship of both condylar heads after wearing CD (p<0.01). Before wearing CD, the average horizontal angle of long axis of condylar head was 79.6+/-2.7degrees and 80.1+/-5.7degrees respectively on the right and left sides. After wearing CD, both condyles were rotated in the same direction in average on axial plane. CONCLUSION: We observed with CBCT the significant clinical evidence in case of positional change of mandibular condyle after wearing complete denture.

A comparison of transcranial with panoramic TMJ radiographs to assess the movement of the mandibular condyle / 대한구강악안면방사선학회지

PURPOSE: To evaluate the difference of the movement of the mandibular condyles between transcranial and panoramic TMJ radiographs to view the movement of the mandibular condyles. MATERIALS AND METHODS: Thirty-four paired transcranial and panoramic TMJ radiographs of patients were used to evaluate the movement of the mandibular condyle. The distances, from the most superior point of the mandibular condyle to the most inferior point of the articular eminence on both radiographs, were measured. The measurements were taken at closed state and maximum opening state of each radiograph on both side. Differences between matched pairs were analysed by paired t-test, with significance established at P<0.05. RESULTS AND CONCLUSION: The mean distance, from the most superior point of the mandibular condyle to the most inferior point of the articular eminence on both radiographs, was statistically different at each side (P<0.05). At closing state, the mean distance measured on panoramic TMJ radiographs was longer than on transcranial radiographs (0.85 mm at right side, 1.20 mm at left side). But at maximum opening state, the mean distance on transcranial radiographs was longer (1.00 mm at right side, 0.62 mm at left side) than panoramic TMJ radiographs.

Basal cell nevus syndrome: 2 case reports / 대한구강악안면방사선학회지

The basal cell nevus syndrome (BCNS) is an autosomal dominant disorder, characterized by basal cell carcinomas, odontogenic keratocysts and skeletal abnormalities. We experienced two cases that represented several characteristics of BCNS. Case 1: a thirty three year-old man visited CSU hospital. His radiographs showed four cystic lesions at both maxillary sinus and both mandibular angle, with bifid rib and ectopic calcification of falx cerebri. After marsupialization and enucleation, recurrent and newly developing tendency were found on his follow-up radiographs. Case 2: a seventeen year-old man had four large cystic lesions which were diagnosed as odontogenic keratocysts. He had craniofacial anomalies which included ectopic calcification and frontal bossing.

A study of the mandibular canal in digital panoramic radiographic images of a selected Korean population / 대한구강악안면방사선학회지

PURPOSE: To determine the more valuable information to detect the mandibular canal and the mental foramen in panoramic radiographs of a selected Korean population for the implant. MATERIALS AND METHODS: This study analysed 288 panoramic radiographic images of patients taken at the Dental hospital of Chosun University retrospectively. Indirect digital panoramic X-ray machine (ProlineXC, PLANMECA, Finland) with processing by using Directview CR950@ (Kodak, U.S.A.) and Direct digital panoramic X-ray machine (Promax, PLANMECA, Finland) were used for all exposures. All images were converted into Dicom format. RESULTS: The common position of the mental foramen was in line with the longitudinal axis of the second premolar (68.1%). The mental foramen was symmetrical in 81.8% of cases. The mandibular canal was not identified at anterior portion and discontinued with the mental foramen in 27.8% of all cases, in 42.4% identified with lower border line continued with the mental foramen, in 14.6% with both upper and lower border lines, and in 15.3% unilaterally identified with lower border line. CONCLUSION: Clinicians can estimate the upper border line of the mandibular canal from the confirmation of the mental foramen and the lower border line of the mandibular canal symmetrically on the panoramic radiography taken in adjusted midsaggital plane of patient's head.

CBCT analysis of three implant cases for treatment planning / 대한구강악안면방사선학회지

The role of radiographic imaging in determining the size, numbers and the position of implants is very important. To perform the implant procedure, the dentist needs to evaluate the bone pathology and bone density, and to know the precise height, width, and contour of the alveolar process, as well as its relationship to the maxillary sinus and mandibular canal. The author analyzed 3 implant cases for treatment planning with the cone beam CT. All axial, panoramic, serial and buccolingual-sectioned images of 3 cases with stent including vertical marker were taken by using Mercuray (Hitachi, Japan). When the curved line drawn intentionally did not include dot image of a vertical marker on the axial image of CBCT, the image of the vertical marker was deformed on its buccolingually sectioned image. There was wide discrepancy in inclination between the alveolar bone and tooth on buccolingually sectioned image.

Developmental salivary gland defect: Literatures review and case analysis of 12 cases / 대한구강악안면방사선학회지

PURPOSE: To review developmental salivary gland defect based on 12 reported cases and literature, and to guide radiographic diagnosis of this entity. MATERIALS AND METHODS: The 12 cases of developmental salivary gland defect of Chosun University Dental Hospital in the last 4 years were analyzed and compared with previous reported cases. RESULT: 11 of the 12 cases were found in men, indicating a very strong male predilection. The peak age was in the 6th decade. These defects were situated just above or at the inferior border of mandible between the first molar and the mandibular angle, and always inferior to the mandibular canal. Only one case was superimposed with the mandibular canal, 6 cases were superimposed with the inferior border of the mandible. CONCLUSION: Characteristically, these defects had a special radiographic features such as ovoid shaped well-defined radiolucency located just above or at the inferior border of the mandible between the first molar and the mandibular angle, and always inferior to the mandibular canal. The recognition of these radiographic features were diagnostically valuable.

Myofibroma of the mandible: A case report / 대한구강악안면방사선학회지

Myofibroma is a rare benign soft tissue tumor that in all ages usually occurs in the head and neck region, and at subcutaneous tissue, but rarely has bone origin within bone. Intraosseous lesions are more often found in childhood. Although intraosseous lesions are relatively common in mandible. Reports for mandible, reports on radiographic findings of myofibroma occurred on the mandible are uncommon. We describe the radiographic appearance on the conventional radiographs and CT of myofibroma of the mandible in a 9-year-old boy. This benign lesion closely resembles to odontogenic cyst or tumor on image.

Influence of Lens Factor and Effect of Selected Cataract Extraction on Acute Angle-Closure Glaucoma

PURPOSE: To analyze the affecting factor of lens in pathogenesis of acute primary angle-closure glaucoma (APACG) and the effect of selected cataract extraction with intraocular lens (IOL) implantation. METHODS: A survey was conducted on 25 eyes of 21 patients with acute angle-closure glaucoma accompanied by senile cataract against 21 eyes of 16 age-matched normal persons. Biometric measurements were made in both groups in order to analyze an affecting factor of lens in APACG. Before and after selected cataract extraction, other clinical findings were also evaluated. RESULTS: Biometric measurements such as anterior chamber depth (ACD), lens thickness (LT), ACD/axial length (AXL), LT/AXL, and relative lens position (RLP) were significantly larger for the 25 eyes of the 21 patients with APACG than the 21 eyes of the 16 age-matched normal persons (P<0.05). After selecting cataract extraction with IOL implantation, improved biometric measurements and clinical findings revealed the effectiveness of that operation. CONCLUSIONS: Selected cataract extraction with IOL implantation could be successful as primary surgery in APACG accompanied by senile cataract over intraocular pressure control and visual acuity improvement for lens factor removal of APACG.

Mesiodistal tooth angulation to segmental occlusal plane in panoramic radiography / 대한구강악안면방사선학회지

PURPOSE: To evaluate the stability of the segmental occlusal plane and anatomical line as the reference line for measuring the mesiodistal tooth angulation in panoramic radiography and to determine the mean angle and the range of the mesiodistal tooth angulation in Korean population with normal occlusions. MATERIALS AND METHODS: Twenty nine subjects (15 men, 14 women) with normal occlusion were selected. A total of 29 panoramic radiograms were taken at normal head position and then 10 images of 5 subjects selected were repeatedly taken with repositioning 2 times at each of the head down (V-shaped occlusion) and up (horizontal occlusion) for evaluation of stability of adopted reference lines by using PM2002CC (Planmeca, Finland). The images were traced with adoption of two test reference lines and the long axes of the teeth. The mesial angles formed by each reference line and the long axes of the teeth were measured and analyzed. RESULTS: With anatomical reference line, the mesiodistal tooth angulations of the molars showed the significant difference by over 5 degree between the normal and each changed head position. With segmented occlusal reference line, deviations of mesiodistal tooth angulations by the two changed head positions were less than 1 degree. The means, standard deviations, and maximum and minimum values of mesiodistal tooth angulations to segmental occlusal reference line on panoramic radiography were determined. CONCLUSION: It would appear that mesiodistal tooth angulations to segmental occlusal plane as reference line in panograms are predictable as standards of normal occlusion and useful for evaluation of tooth arrangement between adjacent teeth.

A fractal analysis of bone phantoms from digital images / 대한구강악안면방사선학회지

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 rectangular 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) 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.

Finite element analysis of wide diameter screw implant placed into regenerated bone

The purpose of this study was to investigate the distribution of stress within the regenerated bone surrounding the implant using three dimensional finite element stress analysis method. Using ANSYS software revision 6.0 (IronCAD LLC, USA), a program was written to generate a model simulating a cylindrical block section of the mandible 20 mm in height and 10 mm in diameter. The 5.0 x 11.5-mm screw implant (3i, USA) was used for this study, and was assumed to be 100% osseointegrated. And it was restored with gold crown with resin filling at the central fossa area. The implant was surrounded by the regenerated type IV bone, with 4 mm in width and 7 mm apical to the platform of implant in length. And the regenerated bone was surrounded by type I, type II, and type III bone, respectively. The present study used a fine grid model incorporating elements between 250,820 and 352,494 and nodal points between 47,978 and 67,471. A load of 200N was applied at the 3 points on occlusal surfaces of the restoration, the central fossa, outside point of the central fossa with resin filling into screw hole, and the functional cusp, at a 0 degree angle to the vertical axis of the implant, respectively. The results were as follows: 1. The stress distribution in the regenerated bone-implant interface was highly dependent on both the density of the native bone surrounding the regenerated bone and the loading point. 2. A load of 200N at the buccal cusp produced 5-fold increase in the stress concentration at the neck of the implant and apex of regenerated bone irrespective of surrounding bone density compared to a load of 200N at the central fossa. 3. It was found that stress was more homogeneously distributed along the side of implant when the implant was surrounded by both regenerated bone and native type III bone. In summary, these data indicate that concentration of stress on the implant-regenerated bone interface depends on both the native bone quality surrounding the regenerated bone adjacent to implant and the load direction applied on the prosthesis.