Radiopacity Measurement of Restorative Resins Using Film and Three Digital Systems for Comparison with ISO 4049: International Standard.

This study compared Ultra Speed Occlusal Film (USOF) and 3 digital systems in determining the radiopacity of 5 different restorative resins in terms of equivalents of aluminum thickness. Whether those digital systems could be used to determine whether radiopacity was in line with International Organization for Standardization (ISO) recommendations was also investigated. Disks of each of 5 restorative resins and an aluminum step wedge were exposed at 65 kVp and 10 mA on USOF and imaged with each digital system. Optical density on the film was measured with a transmission densitometer and the gray values on the digital images using Image J software. Graphs showing gray value/optical density to step wedge thickness were constructed. The aluminum equivalent was then calculated for all the resins using a regression equation. All the resins were more radiopaque than 1 mm of aluminum, and therefore met the ISO 4049 recommendations for restorative resins. Some resins showed statistically higher aluminum equivalents with digital imaging. The use of traditional X-ray films is declining, and digital systems offer many advantages, including an easy, fast, and reliable means of determining the radiopacity of dental materials.

Characteristic findings on panoramic radiography and cone-beam CT to predict paresthesia after extraction of impacted third molar.

The purpose of this study was to compare findings on the relationship between impacted molar roots and the mandibular canal in panoramic and three-dimensional cone-beam CT (CBCT) images to identify those that indicated risk of postoperative paresthesia. The relationship between impacted molars and the mandibular canal was first classified using panoramic images. Only patients in whom the molar roots were either in contact with or superimposed on the canal were evaluated using CBCT. Of 466 patients examined using both panoramic and CBCT images, 280 underwent surgical extraction of an impacted molar, and 15 of these (5%) reported postoperative paresthesia. The spatial relationship between the impacted third molar root and the mandibular canal was determined by examining para-sagittal sections (lingual, buccal, inter-radicular, inferior, and combinations) obtained from the canal to the molar root and establishing the proximity of the canal to the molar root (in contact with or without loss of the cortical border and separate). The results revealed that darkening of the roots with interruption of the mandibular canal on panoramic radiographs and the inter-radicular position of the canal in CBCT images were characteristic findings indicative of risk of postoperative paresthesia. These results suggest that careful surgical intervention is required in patients with the above characteristics.

Exposure time reduction of secondary radiographs used in digital subtraction radiography in detecting intrabony change.

OBJECTIVES: Digital subtraction radiography (DSR) is a suitable technique for detecting incipient bone changes. However, in DSR, one or more follow-up radiographs must be taken. The aim of this study was to assess the possibility of reducing the exposure time for the radiographs that follow the initial one. METHODS: Maxillary premolar and molar radiographic images of a dry skull were taken with a digital radiography system. The initial radiographs, without bone chips, were taken at 0.32 and 0.16 s. Then, five bone chips (weight range 7-15 mg) were placed on the maxillary molar buccal side of the dry skull. Secondary radiographs were taken at 0.32-, 0.16-, 0.08-, 0.04-, and 0.02-s exposure times. For each bone chip, radiographs were taken three times. The secondary and initial images were subtracted to yield subtraction images. Four observers were asked to evaluate bone change visibility in the subtraction images. The Friedman test was used for statistical analysis. RESULTS: Significant differences were seen at each of the settings for the 0.32-s group (p = 1.24e-030) and 0.16-s group (p = 7.52e-009). By comparing the different groups, observer evaluations indicated that visibility changed when the secondary radiograph was taken at 1/8 of the exposure time of the initial radiograph. In both groups, the visibility of the 0.02-s subtraction image was significantly lower than that of the other subtraction images. CONCLUSION: In DSR, the exposure time of the secondary radiograph can be reduced to 1/4 of the exposure time of the initial radiograph.

Composition of the blood supply in the sublingual and submandibular spaces and its relationship to the lateral lingual foramen of the mandible.

OBJECTIVE: The purpose of this research was to contribute to minimizing arterial disruption during mandibular surgical procedures by clarifying the course of the arteries supplying the sublingual and submental regions. STUDY DESIGN: Heads of 75 human cadavers were dissected to identify the arterial supply of the sublingual and submental regions. Computed tomography scans were performed to visualize the lateral lingual foramina of the mandibles. RESULTS: The facial artery was found to contribute to the composition of almost half of the sublingual arteries studied. Furthermore, it was demonstrated that the arterial supply to an incisor tooth is often from the submental artery. CONCLUSIONS: Our data provide important information for coping with bleeding or hematoma occurring during surgical procedures in the mandibular region.

Retromolar canals as observed on cone-beam computed tomography: their incidence, course, and characteristics.

OBJECTIVE: The study aims at assessing the incidence, course, and characteristics of retromolar canals. STUDY DESIGN: The cone-beam computed tomography images of 171 subjects were evaluated for the presence, course, and pattern of occurrence of retromolar canals. RESULTS: Three types of retromolar canals namely A, B, & C were detected in 129 subjects. Type A branched off the mandibular canal distal to third molar to open into retomolar fossa, type B coursed between retromolar fossa and radicular portion of third molar, type C coursed from mandibular foramen anteroinferiorly to exit into retromolar fossa. The type B retromolar canal presented features distinguishing it from other types. CONCLUSIONS: Considerable number of individuals presented with retromolar canals emphasizing their significance in surgeries involving the retromolar area. The type B pattern, to the best of our knowledge, hasn't been reported by most researchers and hence, could be considered as an additional type of retromolar canal.

The effect of surrounding conditions on pixel value of cone beam computed tomography.

OBJECTIVE: The purpose of this study was to evaluate the reliability of pixel value in CBCT, especially with regard to the effect of surrounding objects that are presented outside the field of view (FOV). MATERIALS AND METHODS: This experiment used the GE Hi-Speed QXi, a multidetector helical computed tomography (MDCT) scanner, and the 3D Accuitomo FPD 8, a cone beam computed tomography (CBCT) scanner. Two types of phantoms were used, both of which contained Lipiodol Ultra Fluid (Lipiodol UF). The type A phantom was a target phantom for pixel value measurement while type B was used for the surrounding environment. For CBCT, the type A phantom was placed in a water bath, and 4 types of surrounding environmental conditions were created: (1) no other phantom present, (2) phantom type B also within the FOV, (3) half of phantom type B within the FOV, (4) phantom type B entirely outside the FOV but within the path of x-rays aimed at phantom A. RESULTS: In MDCT, pixel value (CT number) showed an almost linear correlation with the concentration of Lipiodol UF. In CBCT, on the other hand, pixel value was not linearly correlated with Lipiodol UF concentration. The position of the type B phantom affected pixel values in images of the type A phantom. CONCLUSIONS: Pixel value in CBCT may be affected by various conditions such as beam hardening and surrounding materials, and is therefore not reliable. Caution is essential when pixel values in CBCT are used to estimate bone density at potential implant sites.

Accessory mandibular foramina: a CT study of 300 cases.

PURPOSE: The aim of the study was to assess the distribution of accessory foramina in the mandibular body with computed tomography (CT). MATERIALS AND METHODS: The CT images of the mandibular body in 300 subjects (183 females and 117 males aged between 12 and 85 years) were retrospectively analysed for the presence of accessory foramina. The buccal and lingual surfaces were examined by dividing them into anterior and posterior quadrants. RESULTS: Of the 300 subjects, 26 presented with accessory foramina on buccal posterior aspect and 70 subjects presented on buccal anterior aspect. Further, on the lingual posterior aspect, 132 subjects presented with accessory foramina and 59 subjects presented on lingual anterior aspect. Most of the subjects with accessory foramina in the buccal posterior, buccal anterior and lingual anterior regions had accessory foramina on other aspects of the mandible as well. CONCLUSION: A substantial number of subjects presented with accessory foramina on the lingual posterior aspect when compared to other aspects. Nevertheless, the number of subjects with accessory foramina on other aspects of the mandible was considerable and cannot be ignored. It is suggested that when an accessory foramen is identified in an individual on a particular aspect of the mandibular body, it is highly probable that he will exhibit accessory foramina on other aspects as well.

Influence of horizontal condylar angle and x-ray projection angle on the appearance of the condyle on lateral temporomandibular joint panoramic radiographs.

AIMS: This study used dried human mandibles and aimed to assess the effect of different horizontal condylar angle and the effect of different beam angles from three different units in the depiction of medial, central and lateral parts of the condyle on panoramic and lateral temporomandibular joint (TMJ) panoramic images. METHODS: Standard panoramic and lateral TMJ panoramic images of four dried human mandibles with horizontal condylar angles of 5, 8,10, 15, 17 and 20 degrees were analysed. The different parts of the condyle were represented by radiopaque markers. The standard panoramic and lateral TMJ panoramic images of the four mandibles were acquired from three panoramic radiography models with different x-ray beam angle. The images were analysed for the position of these radiopaque markers. RESULTS: Standard panoramic images demonstrated almost similar images of the condyles in the three panoramic models. The lateral TMJ panoramic images demonstrated the medial pole anterior to the lateral pole when the x-ray projection angle was more than the horizontal condylar angle; superimposition of medial and lateral poles when the x-ray projection angle was equal to horizontal condylar angle; and lateral pole anterior to medial pole when the x-ray projection angle was less than beam projection angle. CONCLUSION: This study demonstrated that apart from other factors, the depiction of the mandibular condyle on lateral TMJ panoramic radiographs depends on the horizontal condylar angle, and the x-ray beam angle, which differs among different manufacturers. Therefore these limitations have to be considered when interpreting the integrity of the mandibular condyle on lateral TMJ panoramic radiographs.

Skeletal maturity assessment with the use of cone-beam computerized tomography.

OBJECTIVE: The aim of the study was to compare cervical vertebrae maturity assessed with the use of cone-beam computerized tomography (CBCT) with the hand-wrist maturation method and cervical vertebrae maturation assessed with the use of lateral cephalography for the assessment of skeletal maturity. STUDY DESIGN: Assessment of skeletal maturation was done using skeletal maturity indicators (SMI) from hand-wrist radiography, cervical vertebrae maturity index (CVMI) from CBCT and lateral cephalography (cephalo-CVMI). The Spearman correlation coefficient was used for statistical analysis. RESULTS: We observed a significant relationship between CBCT-CVMI and cephalo-CVMI as well as between CBCT-CVMI and SMI stages. The Spearman correlation coefficient value between CBCT-CVMI and cephalo-CVMI was 0.975 (P < .0001) and between CBCT-CVMI and SMI was 0.961(P < .0001). CONCLUSIONS: Cervical vertebrae maturity assessment with CBCT provided a reliable assessment of pubertal growth spurt, and therefore CBCT can be used to assess skeletal maturity.

Effects of dose reduction on multi-detector computed tomographic images in evaluating the maxilla and mandible for pre-surgical implant planning: a cadaveric study.

OBJECTIVE: To assess effects of dose reduction on image quality in evaluating maxilla and mandible for pre-surgical implant planning using cadavers. MATERIALS AND METHODS: Six cadavers were used for the study using multi-detector computed tomography (CT) operated at 120 kV and the variable tube current of 80, 40, 20 and 10 mA. A slice thickness of 0.625 mm and pitch 1 were used. Multi-planar images perpendicular and parallel to dentitions were created. The images were evaluated by five oral radiologists in terms of visibility of the anatomical landmarks including alveolar crest, mandibular canal, floors of the maxillary sinus and nasal cavity, contours/cortical layer of jaw bones and the details of trabecular bone. Observers were asked to determine the quality of the images in comparison with 80 mA images based on the criteria: excellent, good, fair or non-diagnostic. The average scores of all observers were calculated for each specimen in all exposure conditions. RESULTS: The 40 mA images could visualize such landmarks and were evaluated to be same or almost equivalent in quality to the 80 mA images. Even the 20 mA images could be accepted just for diagnostic purpose for implant with substantial deterioration of the image quality. The 10 mA images may not be accepted because of the obscured contour caused by image noise. CONCLUSION: Significant dose reduction by lowering mA can be utilized for pre-surgical implant planning in multi-detector CT.

Effects of tube current on cone-beam computerized tomography image quality for presurgical implant planning in vitro.

OBJECTIVE: The purpose of this study was to evaluate the effect of tube current reduction on the quality of cone-beam computerized tomography (CBCT) images of the maxilla and mandible for presurgical implant planning. STUDY DESIGN: Six cadaver heads were imaged with a CBCT (3D Accuitomo) operated at 80 kVp and variable tube current (8, 4, 2, or 1 mA) in full-scan mode. For the posterior region of maxilla and mandible, half-scans were also performed at similar settings. The images were evaluated independently by 5 oral radiologists for 15 anatomic landmarks regarding presurgical implant planning. The quality of images were compared with their respective reference images at 8 mA and ranked on a 4-point rating scale as excellent, good, fair, or nondiagnostic. The scores of all observers were averaged for each landmark at every exposure condition, and Bonferroni test (P<.05) was performed. RESULTS: The 4 mA images at full-scan mode could visualize each landmark of maxilla and mandible and were evaluated to be the same or almost equivalent in quality as the 8 mA images. Even 2 mA images in full-scan mode and 4 mA in half-scan mode could be used for implant planning. The 1 mA images were unacceptable owing to the substantial degradation in image quality. CONCLUSION: Significant dose reduction can be achieved by reducing tube current without substantial loss of image quality for presurgical implant planning in CBCT.

Effect of glypican-1 gene on the pulp cells during the reparative dentine process.

GPC-1 (glypican-1) is a cell surface heparan sulfate proteoglycan that acts as a co-receptor for heparin-binding growth factors and members of the TGF-ß (transforming growth factor beta-1) family. The function of cell-surface proteoglycans in the reparative dentine process has been under investigation. Gpc-1 was detected with similar frequency as tgf-ß1 in the cDNA library using mRNA from the odontoblast-like cell-enriched pulp of rat incisors. The aim of this study was to test our hypothesis that gpc-1 may be related to reparative dentine formation. We examined the expression of this gene during the reparative dentine process, as well as the effect of gpc-1 on odontoblast-like cell differentiation using siRNA (small interfering RNA) to down-regulate gpc-1 expression. Immunohistological examination showed that GPC-1 was expressed in pulp cells entrapped by fibrodentine and odontoblast-like cells as well as TGF-ß1. The mRNAs for gpc-1, -3 and -4, except for gpc-2, were expressed during odontoblast-like cell differentiation in pulp cells. The relative levels of gpc-1 mRNA were increased prior to the differentiation stages and were decreased during the secretory and maturation stages of pulp cells. Down-regulation of gpc-1 expression resulted in a 3.9-fold increase in tgf-ß1 expression in pulp cells and a 0.3-fold decrease in dspp (dentine sialophosphoprotein) expression compared with control. These results suggested that gpc-1 and tgfß-1 expression are necessary for the onset of differentiation, but should be down-regulated before other molecules are implicated in the formation of reparative dentine. In conclusion, gpc-1 expression in odontoblast-like cells is associated with the early differentiation but not with the formation of reparative dentine.

Imaging of the mylohyoid muscle: separation of submandibular and sublingual spaces.

OBJECTIVE: This article focuses on the anatomy of the mylohyoid muscle, a crucial landmark in imaging of the oral cavity and upper neck, showing dissected specimens and CT and MR images. CONCLUSION: Identification of the relationship of a lesion in the sublingual space to the mylohyoid muscle using MDCT and high-resolution MRI is a key part of the imaging assessment of the oral cavity and upper neck.

Effect of computer assistance on observer performance of approximal caries diagnosis using intraoral digital radiography.

Logicon Caries Detector (LDDC) is the only commercially available computer-assisted diagnostic system for caries diagnosis. The object of this study is to elucidate the efficacy of LDDC when used by inexperienced dentists. Fifty extracted teeth were imaged using an RVG6000. Seven dentists who had just passed the Japanese National Dental Board Examination observed those images without LDDC (woLDDC) and assessed the probability that caries lesions were present, then re-assessed the same teeth using LDDC (wLDDC). The areas under the receiver operating characteristic curves (Az) were compared. No statistically significant difference was found between woLDDC Az values and wLDDC Az values when caries lesions of all depths were considered. When positive cases were restricted to caries lesions in the inner half of the enamel or to dentine caries lesions, however, wLDDC Az values were significantly larger than woLDDC (p = 0.043 and 0.018, respectively).

Magnetic resonance signal intensity from retrodiscal tissue related to joint effusion status and disc displacement in elderly patients with temporomandibular joint disorders.

Magnetic resonance imaging (MRI) on patients with temporomandibular joint disorders (TMD) has revealed that a decrease and/or increase in signal intensity from retrodiscal tissue, joint effusion (the excessive accumulation of joint fluid) and articular disc displacement are related to TMD. However, the effect of aging on these phenomena has yet to be clarified. This study was carried out to explore the relationship between changes in signal intensity from retrodiscal tissue, joint fluid status and pathological disc conditions in elderly patients with TMD. Twenty patients aged over 60 years were examined. They consisted of one man and 19 women, and ranged between 60 and 79 years in age (mean, 66.0 years). The relationships between decreased signal intensity on proton-density-weighted (PDW) images and increased signal intensity on T2-weighted (T2W) MR images from retrodiscal tissue, joint fluid status and state of articular disc were examined. Joint fluid status was classified into 5 levels by extent of high signal areas in upper and lower articular spaces on T2W images. Disc displacement status was evaluated by PDW images. The Wilcoxon test was applied for the statistical analysis. The group showing increased T2W signal intensities from the retrodiscal tissue consisted of 31 out of 40 joints (77.5%). This group showed a significant difference in comparison with the other groups in which no apparent joint fluid was shown (p<0.05). There were no statistically significant differences among other categories. The results suggest a negative relationship between joint fluid and increased signal intensity from retrodiscal tissue due to reflection of the inflammatory reaction in TM joints.

Relationship between appearance of a double contour on the mandibular condyle and the change in articular disc position after splint therapy.

OBJECTIVE: The aim was to investigate the relationship between the appearance of double contours on the mandibular condyle and changes in articular disc position after splint therapy. STUDY DESIGN: Panoramic radiographs and magnetic resonance images of 82 joints in 41 patients taken before and after treatment were studied. The number of cases showing a double contour after treatment was compared between the 2 groups with and without disc displacement before treatment, and between the 2 groups with and without reduction in the displacement group; a comparison was also made among age groups and among 3 groups showing improvement, aggravation, or no change in displacement after treatment. RESULTS: All joints showing a double contour after treatment showed articular disc displacement before treatment. No double contours were observed after treatment on joints without articular disc displacement before treatment. All joints showing a double contour showed improvement in disc displacement. CONCLUSION: The results indicate that a double contour on the mandibular condyle is the result of repositioning of, or positional improvement in, a displaced articular disc.

Assessment of the blood supply to the lingual surface of the mandible for reduction of bleeding during implant surgery.

OBJECTIVES: The aim of this study was to assess the frequency of the foramina and their canals on the lingual surface of the mandible using computed tomography (CT), which was carried out for dental implant planning. MATERIAL AND METHODS: First, the visibility of the lingual canals of the CT image was verified by dissecting five cadavers. CT images of 200 patients, who had decided on implant treatment, were used in this study. The visibility of the foramina and their canals on the lingual surface of the mandible were assessed. RESULTS: The foramina were divided into two groups by the positions of the mandible, the medial lingual foramen and the lateral lingual foramen. At least one foramen was found in all patients. In the medial group, a higher level of mental spine was seen in 190 patients, the same level of mental spine was observed in 99 patients and a lower level of mental spine was observed in 114 patients. The lateral lingual foramina were found in 160/200 patients and 88/200 patients presented bilaterally. CT can predict the position and the size of the foramina and their canals on the lingual surface of the mandible. All the patients had more than one foramen in the middle of the lingual surface of the mandible on the CT image. CONCLUSION: The frequency of the lingual foramina in the medial region was 100% and that in the lateral region was 80%. It would also be useful to emphasize the significant variation in the precise location of these lingual foramina, and that these can only be visualized presurgically with volumetric imaging modalities, such as CT or Cone beam 3D systems.

Evaluation of a limited cone-beam volumetric imaging system: comparison with film radiography in detecting incipient proximal caries.

OBJECTIVES: To assess the accuracy of a limited cone-beam volumetric imaging system in detecting incipient proximal caries. STUDY DESIGN: Fifty extracted premolars were used. On 100 surfaces examined, 71 proximal carious lesions were found; 47 were limited to the enamel, and 24 penetrated into the dentin. A limited cone-beam volumetric imaging system (CBVI), 3D Accuitomo (J. Morita Mfg. Corp., Kyoto, Japan), was used. Insight films (Eastman Kodak, Rochester, NY) were used for comparison. Seven experienced oral radiologists determined the presence of lesions using a continuous rating scale. The area measure (Az) values were calculated from the receiver operating characteristic curve obtained for each modality and observer. RESULTS: The mean Az-values were 0.63 +/- 0.02 for 3D Accuitomo and 0.63 +/- 0.03 for film. Analysis of variance showed no statistically significant difference between 3D Accuitomo and film. CONCLUSIONS: A limited CBVI, 3D Accuitomo, could not enhance the accuracy in detecting proximal carious lesions.

Effect of Er,Cr:YSGG laser irradiation on eruption of rat mandibular incisor after disturbance of the enamel organ in the pulp.

To investigate the efficacy of Er,Cr:YSGG (erbium,chromium:yttrium scandium gallium garnet) laser irradiation in root canal preparation and to evaluate its effect on eruption of rat incisors after disturbance of the enamel organ in the pulp, 20 canals of lower left incisor teeth were prepared by K-files followed by Er,Cr:YSGG laser irradiation, and 20 canals of right incisors were subjected to K-files only (control). At 1 week after irradiation, both sides of incisors erupted at the same level from the gingival margin. Histological findings showed that laser irradiation produced a slightly larger damage in the pulp than that of control. Scanning electron microscope observation revealed that laser-treated surface revealed a rough, irregular, and very clean surface; there was almost no evidence of debris or smear layer, and dentinal tubules were opened. Adequate power of Er,Cr:YSGG laser irradiation is effective in root canal preparation without disturbance of the eruption.

Accuracy of extraoral tuned aperture computed tomography (TACT) for proximal caries detection.

OBJECTIVES: The objectives of this study were to compare the difference in the accuracy of proximal caries detection by extraoral tuned aperture computed tomography (TACT), intraoral TACT, and film radiographs. STUDY DESIGN: Eighty proximal surfaces of 40 extracted human maxillary teeth were used. A digital sensor was the image receptor for TACT. Film radiographs were acquired using Insight film. Nine basis images were acquired to reconstruct TACT slices. Seven observers scored the presence or absence of proximal caries using the 3 imaging modalities. The true presence of caries and its depth were determined using the sectional images obtained by micro CT. Among the image modalities and observers, possible differences in the area under the receiver operating characteristic curve were assessed by analysis of variance (ANOVA). RESULTS: ANOVA indicated no statistically significant differences between observers (P = .845), modalities (P = .657), and observer-modality combinations (P = .593). CONCLUSION: Within the limited range of this study, extraoral TACT was not statistically different from intraoral TACT or film radiographs for proximal caries detection. This suggests that extraoral TACT may have some clinical utility for caries diagnosis and that further study may be warranted.