Chinami Igarashi

Accuracy of intraoral radiography, multidetector helical CT, and limited cone-beam CT for the detection of horizontal tooth root fracture.

OBJECTIVE The accuracies of intraoral radiography (IOR), multidetector helical computerized tomography (MDHCT) at slice thicknesses 0.63 mm and 1.25 mm, and limited cone-beam computerized tomography (LCBCT) were compared for detection of horizontal tooth root fracture. STUDY DESIGN In 7 beagle dogs, 28 maxillary anterior teeth were used, of which 13 had artificially induced horizontal root fracture. The specimens were examined by the above-mentioned 4 modalities. Diagnosis of root fracture was based on direct visualization of radiolucent line in each image by 6 radiologists. RESULTS Sensitivity, negative predictive value, and diagnostic accuracy (true positives + true negatives) for detecting fracture lines in LCBCT (0.96 +/- 0.04, 0.97 +/- 0.03, 0.93 +/- 0.04, respectively) were significantly higher than MDHCT at 0.63 mm (0.76 +/- 0.09, 0.8 +/- 0.05, 0.8 +/- 0.05, respectively), MDHCT at 1.25 mm (0.49 +/- 0.09, 0.66 +/- 0.04, 0.69 +/- 0.05, respectively), and IOR (0.51 +/- 0.18, 0.67 +/- 0.08, 0.69 +/- 0.08, respectively). Specificity and positive predictive value showed no significant intermethod difference among the 4 modalities. CONCLUSION Limited cone-beam CT is more useful than the other 3 radiographic modalities for diagnostic imaging of horizontal tooth root fracture.

Accuracy of oral mucosal thickness measurements using spiral computed tomography.

BACKGROUND Assessment of oral mucosal thickness is important in implant surgery; however, examining the soft tissue three dimensionally is difficult. A reamer method is invasive, and a non-invasive ultrasonic method produces only low-resolution images depending on anatomic variations. The emerging technology of spiral computed tomography (CT) is an alternative to the conventional methods. Spiral CT has been a useful diagnostic tool in implant surgery. Although it delivers high radiation doses, spiral CT provides three-dimensional imaging of low-contrast structures. The purpose of the present study is to assess the accuracy of oral mucosal measurements using spiral CT. METHODS Thickness of maxillary oral mucosa was measured in five cadavers. The measurement sites were set up in buccal, palatal, and middle of the crest in the missing tooth area in the incisor, canine, premolar, and molar regions. Each cadaver was exposed to spiral CT after installing the measurement guide. After that, each site was physically measured by reamer. Linear regression and correlation analysis were performed to describe the association between radiographic and physical measurements. RESULTS A total of 114 measurements were performed with statistical analyses. Mean values and standard deviations of physical and radiographic measurements were 3.12 ± 1.43 and 2.83 ± 1.70 mm, respectively. The radiographic and physical measurements demonstrate strong correlation (r = 0.90; P <0.01). Measurement error was 0.52 ± 0.36 mm. According to the regions, the measurements in buccal, palatal, and missing tooth region depicted a significant correlation (r = 0.92, r = 0.85, and r = 0.91, respectively). The boundary of the bone and mucosa was indistinguishable at 23 buccal sites. Twenty-three measurements that could not be distinguished with CT had a mean of 0.69 and standard deviation ± 0.13 mm. CONCLUSIONS The correlation between spiral CT and physical measurement was high except in sites of very thin mucosa. Spiral CT can be considered an alternative method for the measurement of oral mucosal thickness. Because of the higher radiation exposure, caution should be exercised and radiation dosage versus clinical benefit assessment is required.

Double mental foramina of the mandible on computed tomography images: a case report

Double mental foramina found with preoperative computed tomography (CT) prior to implant therapy are reported and discussed in reference to literature reports. A 52-year-old man visited us for implant therapy. Preoperative panoramic radiography and CT were conducted. A multisection reconstructed sagittal image showed two mental foramina leading to the mandibular canal on the right side of the mandible, which were diagnosed as double mental foramina. The incidence of double mental foramina reported in the literature is approximately 6.9% in dry Japanese skulls. Many reports have indicated that non-Caucasians have a higher incidence than Caucasians. The general incidence ranges from 2% to 10%. However, only one clinical case report is available.

Magnetic resonance imaging of the temporomandibular joint: a study of inter- and intraobserver agreement

ObjectiveThe purpose of this study was to estimate the inter- and intraobserver agreement for interpreting magnetic resonance (MR) images of the temporomandibular joint (TMJ).MethodsThe study was based on MR images of 30 TMJs. The images were interpreted by seven observers for disk configuration, disk position, joint fluid, bone marrow changes, and diagnosis. The observers were not calibrated. Kappa statistics were used.ResultsThe kappa values were, for interobserver agreement of disk configuration, 0.10; for disk position in the sagittal plane with closed mouth, 0.35; for a combination of closed mouth and open mouth, 0.44; for disk position in the coronal plane, 0.17; for joint fluid, 0.36; for bone marrow changes, 0.01; and for diagnosis, 0.39. Intraobserver agreement was generally higher than interobserver agreement.ConclusionAgreement on disk position in the sagittal plane, on presence and amount of joint fluid, and on diagnosis was fair to moderate. Agreement on disk configuration, on disk position in the coronal plane, and on bone marrow changes was poor.

A case of venous malformation of the mandible

ObjectiveVascular malformations occur more rarely in bones than in soft tissue, with 0.5–1.0% of all intraosseous tumors occurring in the mandible. We report a diagnostically challenging case of unilocular venous malformation of the mandible.Case reportA 76-year-old man presented with a heterogeneous, unilocular, radiolucent lesion with a well-defined border. Panoramic radiography and computed tomography imaging revealed a continuous white line on the cortical bone at the inferior border of the left mandibular molar region. A spherical lesion with a well-defined border and a clear round region in the left mandible were revealed on magnetic resonance imaging. The lesion had the same signal intensity as muscles on T1-weighted imaging, a homogeneous high-intensity signal on short T1-inversion recovery imaging, and a well-defined low-signal intensity region surrounded by a high-intensity signal region on T2-weighted imaging. Pathological findings indicated that the lesion was a venous malformation.DiscussionAlthough many studies have reported that venous malformations have a multilocular appearance, few have described the occurrence of unilocular lesions. Future investigations using magnetic resonance imaging and computed tomography are needed to increase the diagnostic accuracy for unilocular central vascular malformations of the jaw bone.

Artifacts on temporomandibular joint MR images caused by mascara used as hair dye

We report the case of a patient who used mascara in an unusual manner, as hair dye, causing artifacts on magnetic resonance (MR) images. A 60-year-old woman was referred to our hospital because of discomfort and mastication difficulty as a result of dislocation of the mandible on the left side. After a general examination, she was diagnosed with temporomandibular joint disorder and MR imaging was performed. The images showed artifacts in the bilateral temporal regions, although the patient had not undergone surgical treatment in the region and there were no metal hair accessories. However, mascara had been applied to the region to dye the patient’s hair black. To verify that mascara could be the cause of the artifacts in the temporomandibular area, we performed mock MR imaging using a phantom and mascara. Artifacts were also observed in the area with mascara, confirming that the mascara caused the artifacts during MR imaging. This case suggests that care should be taken during MR imaging when different cosmetics are used in the head and neck region.

Quantitative measurements of the articular areas of mandibular condyles with temporomandibular joint disorders using magnetic resonance imaging.

Objective: The authors sought to clarify the variation in the condylar anterior functional surface (AFS) of patients with temporomandibular joint (TMJ) disorders using quantitative measurements by magnetic resonance imaging (MRI). Methods:MR images of 68 joints (2 males, 32 females) were used. The subjects were classified into three groups: with/without defects of cortical bone groups and a combination group without defects. The AFS was measured as the length between the protrusive point and the apex of the condyle on MRI (4-mm-thick slices), and the quad value of the length was defined as the area on the slice. The summed quad values of all slices were used as the AFS area. Differences in the areas among the three groups were compared by one-way analysis of variance (ANOVA). Results:The non-defect group had significantly larger AFS areas than the defect group. Conclusions:Quantitative measurement on MR images clarified the changes in the condylar sagittal appearance.

Effectiveness of a radiology-anatomy instructional module in a clinical course on oral radiology

ObjectivesAn insufficient knowledge of anatomy often complicates the interpretation of radiological findings by students learning clinical medicine. During a 3-week clinical course in oral radiology, students attended lectures on anatomy for half of each day. Our objectives were to evaluate this program and determine why some students remained unmotivated to learn anatomy.MethodsSurveys were carried out using two questionnaires, one for evaluating the students’ beliefs regarding the necessity of knowing anatomy and their understanding of radiology and anatomy, and the other for determining the value of the educational program. In total, 126 questionnaires were analyzed. Structural equation modeling and decision analysis were used to analyze the data obtained.ResultsBeliefs regarding the necessity of knowing anatomy were explained by three variables: the necessity of knowing imaging anatomy, the necessity of knowing gross anatomy, and understanding of anatomy. Awareness of the necessity of knowing anatomy and understanding of graphical images were not strongly correlated. The educational program was characterized by two factors: “value” and “appropriateness” These were strongly correlated. Student interest in the content of the course was found to be the most important factor in student evaluations of the educational program. Students who answered “agree”, “disagree” or “strongly disagree” to three items, “interested in the content of the course”, “obtained knowledge through the course” and “expected the course to be useful in the near future” were likely to have insufficient understanding of and awareness of the necessity of radiology and anatomy.ConclusionsThe inclusion of lectures on anatomy is beneficial for improving student understanding of oral radiology. Student interest in the content is important in evaluations of radiology–anatomy programs.