Objective: The salivary glands play an important role in oral health, and therefore, correct diagnosis and treatment of conditions that affect them are essential. The minor salivary glands are important structures in the oral cavity; however, little is known about their normal imaging findings, especially on ultrasonography. Knowledge of the normal imaging findings of the minor salivary glands is required to aid the diagnosis and treatment of salivary gland conditions. In this study, we aimed to assess the normal ultrasonographic findings of the minor salivary glands.
Material and methods: Twenty healthy adult volunteers, who had no subjective oral symptoms, including a dry mouth, were included in this study. Intraoral ultrasonography scans were performed using a hockey stick-shaped intraoperative linear probe. The following criteria were used to identify the glandular lobes of the minor salivary glands on ultrasonography: an oval or spindle-shaped structure, with an internal echo that was lower than that of the surrounding adipose tissue and higher than that of the surrounding muscles.
Result: On intraoral ultrasonography, the glandular lobes of the upper and lower labial glands were clearly visualized in all subjects. In the lower lip, the glandular lobes were typically found near the facial artery, and the mean lengths of their major and minor axes were 8.4mm and 2.2mm, respectively. In the upper lip, the glandular lobes were slightly smaller than those in the lower lip （mean lengths of the major and minor axes: 5.2mm and 1.5mm, respectively）. The glandular lobules of the anterior lingual gland were symmetrical in the anterior part of the lower surface of the tongue, and the mean lengths of their major and minor axes were 7.2mm and 2.7mm, respectively. The buccal, palatal, and molar glands were difficult to visualize, and therefore, no typical images of these structures were obtained.
Conclusion: This study is the first to attempt to describe the normal intraoral ultrasonographic findings of the minor salivary glands. A more sophisticated ultrasound probe that allows all minor salivary glands to be visualized and has an optimized size and shape for intraoral scanning is required.

View full abstract

Background and Purpose: In recent years, a titanium-zirconium alloy（Ti-ZrO₂）showing improved mechanical properties compared with commercially pure titanium（Ti）has been introduced. On magnetic resonance imaging（MRI）, metal artifacts of dental implants often make diagnosis difficult in clinical situations. Therefore, it is very important to compare metal artifacts of Ti and Ti-ZrO₂ dental implants using MRI. However, few studies have made this comparison. The purpose of this study was to investigate and compare metal artifacts of titanium and Ti-ZrO₂ dental implants.
Materials and Methods: The phantom used in this study was composed of a hollow cylinder with an outer diameter of 20.0cm, and a removable rod of 1.0cm in diameter was placed along the phantom’s central axis. Ti and Ti-ZrO₂ alloy implants were placed on this rod. All subjects underwent imaging with a 1.5T MR scanner（Intera Achieva® 1.5T: Philips Medical Systems, Best, The Netherlands）with a SENSE head 8-channel coil. The imaging sequences included turbo spin echo（TSE）T1-weighted imaging（T1WI）, TSE T2-weighted imaging（T2WI）, short tau inversion recovery（STIR）, and single shot echo planar imaging diffusion-weighted imaging（DWI）. The full width at half maximum （FWHM） of metal artifact in each phase-encoding direction and frequency-encoding was measured on Image J. The Mann-Whitney U test was used to compare FWHM between Ti and Ti-ZrO₂ implants. p-values less than 0.05 were considered to indicate significance.
Results: The phase-encoding direction and frequency-encoding of FWHM were significantly different between Ti and Ti-ZrO₂ implants on T2WI（p ＜0.01）and DWI（p＜ 0.05）. There was no significant difference between each material on T1WI and STIR imaging.
Conclusions: This study suggested that the Ti-ZrO₂ implant is affected by metal artifacts less than the Ti implant on MRI.

View full abstract

Background and Purpose: Joint disc disorders can cause morphological changes in the mandibular condyle due to direct contact between the mandibular condyle and joint nodules. It has been reported that changes in bone marrow signals occur in mandibular condyles that have undergone morphological changes. However, few studies have examined the relationships that exist among temporomandibular joint （TMJ） disk position, disk reduction, and mandibular condyle bone marrow signals. The purpose of this study was to investigate the relationships among these factors using magnetic resonance imaging.
Materials and Methods: In total, 431 patients with temporomandibular disease who underwent MRI examinations of their TMJs at our hospital between April 2016 and March 2018 were included in this study. TMJ disk disorders were classified into anterior disk displacement with reduction and anterior disk displacement without reduction. The bone marrow of the mandibular condyle was classified as normal or abnormal. Statistical analyses were performed with the χ2 test, and p-values of ＜0.05 were considered statistically significant.
Results: Twenty-seven TMJs without disk displacement did not exhibit bone marrow signal abnormalities in the mandibular condyle. Of the 489 joints with anterior disk displacement with reduction, 30 and 459 joints did and did not display signal abnormalities, respectively. In addition, of the 338 joints with anterior disk displacement without reduction, 114 and 224 did and did not exhibit signal abnormalities, respectively. The χ2 test indicated that there was a significant association between TMJ disk displacement with reduction and mandibular condyle bone marrow signals （p＜0.01）.
Conclusions: The present study suggested that relationships exist among TMJ disk position, disk reduction, and bone marrow signals from the mandibular condyle.

View full abstract

Intraoral X-ray images are the most frequently used imaging modality in dentistry. Intraoral X-ray images were classified based on the ten anatomical regions using deep-learning artificial intelligence. A total of 2500 intraoral images from 250 full-mouth intraoral X-ray examinations were used. The LeNet-type deep learning function of the Neural Network Console （Sony Network Communications, Inc.） was employed. The Structure Search function was used to optimize the structure of the convolutional neural network. Ninety-eight percent of the images were classified successfully when each image was in the proper orientation, and the equivalent figure was 88％ when half of the images were randomly rotated. These results suggested that automatic alignment of intraoral X-ray images is possible.

View full abstract

Background and Purpose: Diffusion-weighted imaging （DWI） is used to differentiate between benign and malignant tumors in the maxillofacial region and is less commonly used to examine the temporomandibular joints （TMJs）. The apparent diffusion coefficient （ADC） is a quantitative parameter that is used for tissue characterization. The purpose of the present study was to assess the condylar bone marrow of patients with TMJ disorders using DWI.
Materials and Methods: We designed and performed a retrospective cohort study, which was approved by our university ethics committee （EC15-12-009-1）. The study group comprised 57 patients （12 males, 45 females; 20-81 years of age, mean age: 49.81 years） with a total of 111 TMJs that were examined by MRI. Bone marrow ADCs were compared between various conditions affecting the TMJ using Mann-Whitney’s U test, multiple regression analysis, and the Shapiro-Wilk test. Furthermore, correlations were calculated using the mandibular condyle bone marrow ADC as the predictive variable and condylar joint effusion, or condylar deformities and erosion as explanatory variables.
Results: The mean ADC values of the condylar bone marrow were significantly higher in cases involving joint effusion, osteophyte formation, flattening, or erosion in the mandibular condyle （P＜0.05）.
Conclusion: Mandibular condyle bone marrow ADC values exhibit significant associations with joint effusion, and deformities and erosion in the mandibular condyle. Our results could aid the diagnosis of TMJ disorders.

View full abstract