Morphological analysis of mandibular posterior edentulous bones using cross-sectional CT images / 대한구강악안면방사선학회지

PURPOSE: The purpose of this study was to evaluate the morphologic features of posterior edentulous mandible for Korean patients using cross-sectional CT images. MATERIALS AND METHODS: Computed tomographic cross-sectional views taken in 2004 and 2005 at Seoul National University Dental Hospital were analyzed by an oral and maxillofacial radiologist. Four indices were measured to meet the purpose of this study: 1) the horizontal distance between the alveolar crest and mandibular canal (Type), 2) the angle of the mandibular long axis (Angle), 3) the bucco-lingual location of mandibular canal, and 4) the depth of the submandibular fossa. The averages and standard deviations of the measurements were compared according to the location (the first and second molar area) and sex of the patients. RESULTS: Statistically significant difference was found in Type, Angle, and submandibular fossa depth between the first and second molar area (p.0.05). However, there was no significant difference between men and women in any of the measured indices. Most of the mandibular canals were located in lingual side of posterior mandible. CONCLUSION: More care should be taken when an implant is installed on the mandibular second molar area.

A study of panoramic focal trough for the six-year-old child / 대한구강악안면방사선학회지

PURPOSE: To make a focal trough (image layer) for an average maxillary dental arch of 6-year-old korean in panoramic radiography. MATERIALS AND METHODS: Phantom for the maxillary dental arch was designed using intercanine width, intermolar width, tooth size, and interdental spacing to record the data of 6-year-old child. The characteristics of pre-corrected panoramic machine (for adult) was evaluated using the phantom, resolution test pattern for margin of the image layer, and metal ball for the center of the image layer. Panoramic image layer of the child was developed by means of decreasing the speed of film-cassette and positioning the phantom backwards, and then the characteristics of post-corrected panoramic machine (for child) were reevaluated. RESULTS: At post-corrected panoramic image layer, beam projection angles at all interdental areas increased for about 2.6-3.8 degrees, the position of the image layer was shifted toward the rotation center for about 2.5 mm at the deciduous central incisior area. The width of image layer decreased at all areas. CONCLUSION: Increased beam projection angle will reduce the disadvantage of tooth overlap, and the same form between the center of the image layer and dental arch will improve image resolution.

Effect of irradiation on cell cycle, cell death and expression of its related proteins in normal human oral keratinocytes / 대한구강악안면방사선학회지

PURPOSE: To investigate the radiosensitivity of the normal human oral keratinocytes (NHOK), and the effect of irradiation on cell cycle and protein expression. MATERIALS AND METHODS: To evaluate the radiosensitivity of NHOK, the number of colonies and cells were counted after irradiation and the SF2 (survival fraction at 2 Gy) value, and the cell survival curve fitted on a linear-quadratic model were obtained. LDH analysis was carried out to evaluate the necrosis of NHOK at 1, 2, 3, and 4 days after 2, 10, and 20 Gy irradiation. Cell cycle arrest and the induction of apoptosis were analyzed using flow cytometry at 1, 2, 3, and 4 days after 2, 10, and 20 Gy irradiation. Finally, proteins related cell cycle arrest and apoptosis were analysed by Western blot. RESULTS: The number of survived cell was significantly decreased in a dose-dependent manner. The cell survival curve showed SF2, alpha, and beta values to be 0.568, 0.209, and 0.020 respectively. At 20 Gy irradiated cells showed higher optical density than the control group. After irradiation, apoptosis was not observed but G2 arrest was observed in the NHOK cells. 1 day after 10 Gy irradiation, the expression of p53 remained unchanged, the p21 (WAF1/Cip1) increased and the mdm2 decreased. The expression of bax, bcl-2, cyclin B1, and cyclin D remained unchanged. CONCLUSION: These results indicate that NHOK responds to irradiation by G2 arrest, which is possibly mediated by the expression of p21 WAF1/Cip1, and that cell necrosis occurs by high dose irradiation.

A case of pilomatrixoma in the cheek / 대한구강악안면방사선학회지

We report a case of pilomatrixoma presenting in the right cheek of a 6-year-old girl. In the panoramic view, a small, ovoid-shaped, and nonhomogenous calcified mass was superimposed on the right mandibular angle. The mass was located on the skin overlying the right mandibular ramus area in the skull P-A view. The tumor had a strongly reflective pattern with acoustic shadowing in sonographic view. We also illustrate how these lesions can be effectively diagnosed.

Effect of retinoic acid on the radiosensitivity of normal human oral keratinocyte / 대한구강악안면방사선학회지

PURPOSE: To evaluate the effect of all-trans-retinoic acid (ATRA) on the radiosensitivity of normal human oral keratinocyte (NHOK). MATERIALS AND METHODS: Relative cell survival fraction including SF2 (survival fraction at 2 Gy) was calculated on the basis of colony formation assay. Data were fitted to the linear-quadratic model to establish the survival curve and calculate alpha and beta values. Using flow cytometry at 1, 2, 3, 4, and 5 days after exposure to 2 and 10 Gy irradiation, cell cycle arrest and apoptosis were analysed. To understand the molecular mechanism of the radiosensitization of ATRA on NHOK, proteins related with apoptosis and cell cycle arrest were investigated by Western blot analysis. RESULTS: Treatment with ATRA resulted in a significant decrease of SF2 value for NHOK from 0.63 to 0.27, and increased alpha and beta value, indicating that ATRA increased radiosensitivity of NHOK. ATRA increased LDH significantly, but increasing irradiation dose decreased LDH, suggesting that the radiosensitizing effect of ATRA is not directly related with increasing cell necrosis by ATRA. ATRA did not induce appotosis but increased G2 arrest after 10 Gy irradiation, implying that the increased radiosensitivity of NHOK may be due to a decrease in mitosis casued by increasing G2 arrest. ATRA inhibited the reduction of p53 at 3 days after 10 Gy irradiation and increased p21 at 1 day after 10 Gy irradiation. Further study is required to determine the precise relationship between this effect and the radiosensitizing effect of ATRA. CONCLUSION: These results suggested that ATRA increase radiosensitivity by inhibiting mitosis caused by increasing G2 arrest.

Eagle's syndrome: report of two cases using computed tomography / 대한구강악안면방사선학회지

Two cases of Eagle's syndrome are reported. The first case involved a 31-year-old man who complained of pain in his throat and pain at preauricular area on turning his head. Panoramic and computed tomography (CT) views showed bilateral stylohyoid ligament ossification. The symptoms were relieved after surgical removal. The second case involved a 56-year-old female whose chief complaints were a continuous dull pain and occasional "shooting" pain on lower left molar area. During the physical examination, an ossified stylohyoid ligament was palpated at the left submandibular area. Panoramic and CT images showed prominent bilateral stylohyoid ligament ossification. CT scans also showed hypertrophy of left medial and lateral pterygoid muscles. The symptoms were relieved after medication. CT is a useful tool for the examination of ossified stylohyoid ligaments and studying the relationship between Eagle's syndrome and adjacent soft tissue.

The effect of mandibular position and gantry angle on the evaluation of implant site with implant CT / 대한구강악안면방사선학회지

PURPOSE: The altered gantry angle during scanning for some multiplanar reconstruction CT program (CT/MPR) may cause distortion of the image. The aim of this study was to ascertain whether there is a image distortion in a reformatted image when the gantry and the object are equally inclined using ToothPix and DentaScan program. MATERIALS AND METHODS: A resin block model with four cylindrical holes and a human dry mandible were used. Two MPR software packages, ToothPix and DentaScan program, were used for reformatted panoramic images. The block and the gantry were equally inclined at 0degree, 15degrees, and 30degrees. RESULTS: With ToothPix program, a resin block model with empty holes and a dry mandible showed inclined images in the reformatted panoramic image. Increasing the gantry angle, the depth and inclination of the holes were increased in the reformatted central panoramic images. However, a resin block model with gutta percha in its holes and a dry mandible with a wire in its mandibular canal didn't show image distortion. With DentaScan program, image distortion was not seen in any situation. CONCLUSION: ToothPix program may distort the reformatted image when the gantry angle is not at zero degrees. However, with DentaScan program, the patient may be positioned comfortably and the gantry can be adjusted to the patient positioning.

Evaluation of the mandibular asymmetry using the facial photographs and the radiographs / 대한구강악안면방사선학회지

PURPOSE: To assess the relationship between soft tissue asymmetry and bone tissue asymmetry using the standardized photographs and the posteroanterior (PA) cephalometric radiographs in mandibular asymmetric patients. And to clarify that the lack of morphologic balance among different skeletal components can often be masked by compensatory soft tissue contributions. METHODS: Experimental group consisted of 58 patients whose chief complaints were facial asymmetry, they were taken with standardized facial photographs and PA cephalometric radiographs. Control group consisted of 30 persons in the normal occlusion. The reproducibility of the facial photograph was confirmed by model test. The differences of fractional vertical height and horizontal width from standardized facial photographs and PA cephalometric radiographs were compared and analyzed. RESULTS: The difference of fractional vertical bone height was 0.63 and fractional vertical soft height was 0.58 in control group, 3.10 and 2.01 in asymmetric group, respectively. The difference of fractional horizontal bone width was 0.52 and fractional horizontal soft width was 0.70 in control group, 2.51 and 1.70 in asymmetric group, respectively. Both soft and bone tissue showed significant difference between control and asymmetric group (p<0.05). The difference of bone tissue was greater than that of soft tissue (p<0.05) in the experimental group but, not in control group. CONCLUSIONS: Soft tissue components may compensate for underlying skeletal imbalances.

The relationship among reference lines used for taking the extraoral radiography / 대한구강악안면방사선학회지

PURPOSE: The aim of present study is to estimate the relationship among reference lines used for taking the extraoral radiography and panoramic radiography. MATERIALS AND METHODS: Lateral cephalographs of 40 adults, aged 22 to 30 years were taken. Angles between reference lines (Frankfort line, canthomeatal line, infraorbitomeatal line, and occlusal plane) were measured. RESULTS: Angles between Frankfort line and canthomeatal line, Frankfort line and infraorbitomeatal line, Frankfort line and occlusal plane, canthomeatal line and infraorbitomeatal line, canthomeatal line and occlusal plane, and infraorbitomeatal line and occlusal plane were 16.1degrees(+/-2.2), 5.8degrees(+/-2.4), 8.7degrees(+/-3.5), 10.3degrees(+/-1.3), 24.8degrees(+/-4.0), and 14.5degrees(+/-4.4), respectively. CONCLUSION: Angle between frankfort and canthomeatal line is very different with commonly known angle. Frankfort horizontal reference lines used for panoramic radiography need an exact definition and more accurate standard is needed for the taking of panoramic radiograph

The absorbed doses from each exposure program of the Orthopos(R) panoramic machine / 대한구강악안면방사선학회지

PURPOSE: The objective of this study was to estimate the radiation absorbed doses in certain critical organs in the head and neck region with 16 imaging programs available on the Orthopos(R) panoramic machine. MATERIALS AND METHODS: A Rando phantom and LiF TLD chips were used for dosimetry. The absorbed doses were measured at the thyroid gland, the submandibular gland, the parotid gland, the mouth floor, the maxillary sinus, the brain, the mandibular body, the mandibular ramus, the 2nd cervical spine and the skin over TMJ area. RESULTS: The overall absorbed doses with imaging programs available on the Orthopos(R) panoramic machine were much less than that of standard program (program 1) except program 8, 11, and 16. Generally, the absorbed doses to the bone marrow of the mandibular ramus and the parotid gland were high, but the absorbed doses to the bone marrow in the mandibular body, brain, maxillary sinus, and, especially, the thyroid gland were very low. CONCLUSION: The modified imaging programs available on the Orthopos(R) panoramic machine can be effectively used in aspect of radiation protection.