Clinical and magnetic resonance imaging findings in patients with and without improvement after mandibular manipulation and conservative physical therapy for temporomandibular joint disorders.

OBJECTIVE: This study compared clinical and magnetic resonance imaging (MRI) findings in patients with anterior disk displacement without reduction (ADDWOR) who improved to anterior disk displacement with reduction (ADDWR) vs. patients who did not improve after mandibular manipulation (MM) and conservative self-administered physical therapy (CSAPT). STUDY DESIGN: Of 15 patients diagnosed with ADDWOR by MRI, 7 improved to ADDWR (WOR-WR) and 8 did not improve (WOR-WOR). The clinical and MRI findings before and after therapy were compared in each group. RESULTS: Significant differences between the groups included age, period of awareness of trismus, and maximum mouth opening (MMO). The MRI findings revealed significant differences in the degree of ADD and morphology of the disk and condyle. MMO significantly improved in the WOR-WR group between initial and follow-up visits. CONCLUSION: Patients who were successfully treated with MM and CSAPT tended to be <30 years old, with a longer period of awareness of trismus, MMO <40 mm, a slight or moderate degree of ADD, no deformity of the disk, and no morphologic change in the condyle. Patients with ADDWOR who are treated with MM and CSAPT require an accurate clinical examination and MRI before treatment.

Inter-observer reliability in cone-beam computed tomography assessment of the retromolar canal: A practical plan to improve diagnostic imaging.

Purpose: This study aimed to investigate inter-observer reliability among observers with different levels of proficiency and the diagnostic imaging reliability of cone-beam computed tomography (CBCT) images of the retromolar canal. Materials and Methods: CBCT images of 307 patients were assessed for the presence of retromolar canals (RMCs) by 3 observers independently. Diagnoses were made twice by each observer at intervals of more than 3 weeks. Inter-observer reliability was assessed using the kappa coefficient. One observer had no experience in diagnosis using CBCT images. Therefore, a specialist in diagnostic imaging explained the CBCT images for interpretation and practiced diagnostic imaging together with this observer, while the other observer interpreted the images independently. Thereafter, the observers re-evaluated the images. Results: The interobserver kappa coefficients (including bilateral RMCs) calculated at the first reading were low, ranging from 0.21 to 0.61. Their values ranged from 0.95 (right side) to 1.00 (left side) after one-on-one practice with a diagnostic imaging specialist, while the values ranged from 0.65 (right side) to 0.66 (left side) without one-on-one practice. Conclusion: Diagnostic accuracy was improved through diagnostic imaging practice. To improve the anatomical interpretation of images, it is important to practice diagnostic imaging with a specialist in diagnostic imaging. One-on-one instruction about diagnostic imaging was an effective method of training.

Differential diagnosis between calcifying odontogenic cyst and adenomatoid odontogenic tumor by computed tomography images.

OBJECTIVES: Calcifying odontogenic cysts (COC) and adenomatoid odontogenic tumors (AOT) have similar radiographic findings. We examined the radiographic and computed tomography (CT) images of patients histologically diagnosed with COC or AOT and identified their characteristic findings. METHODS: The subjects included 12 patients histologically diagnosed with COC or AOT (one female and five males per group), who underwent CT at our hospital between Nov 1998 and Jun 2019. The location of the lesion, impacted tooth, bone expansion, root resorption, tooth migration, calcified body, and presence or absence of a high-intensity zone in the marginal area of the lesion were examined. RESULTS: In patients with COC, five patients with COC exhibited bone expansion toward the buccal side. The lesion encompassing the crown was attached to the cement-enamel junction and contained a radiopaque lesion with a calcified body. In 6 patients with COC, irregularly shaped calcified bodies were observed with small tooth-like structures. In patients with AOT, all six patients with AOT exhibited bone expansion toward the buccal and lingual sides. The lesion encompasses a part of the tooth root or the entire tooth. Punctate calcification was observed within the lesion and the marginal area in three patients, and a high-intensity zone was observed in the marginal area of the lesion in two patients. CONCLUSION: We report imaging findings that may be characteristic of COC and AOT, suggesting that CT findings may be useful for differentiating between COC and AOT.

Automatic segmentation of the temporomandibular joint disc on magnetic resonance images using a deep learning technique.

OBJECTIVES: The aims of the present study were to construct a deep learning model for automatic segmentation of the temporomandibular joint (TMJ) disc on magnetic resonance (MR) images, and to evaluate the performances using the internal and external test data. METHODS: In total, 1200 MR images of closed and open mouth positions in patients with temporomandibular disorder (TMD) were collected from two hospitals (Hospitals A and B). The training and validation data comprised 1000 images from Hospital A, which were used to create a segmentation model. The performance was evaluated using 200 images from Hospital A (internal validity test) and 200 images from Hospital B (external validity test). RESULTS: Although the analysis of performance determined with data from Hospital B showed low recall (sensitivity), compared with the performance determined with data from Hospital A, both performances were above 80%. Precision (positive predictive value) was lower when test data from Hospital A were used for the position of anterior disc displacement. According to the intra-articular TMD classification, the proportions of accurately assigned TMJs were higher when using images from Hospital A than when using images from Hospital B. CONCLUSION: The segmentation deep learning model created in this study may be useful for identifying disc positions on MR images.

A case of venous malformation of the mandible.

OBJECTIVE: Vascular 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 REPORT: A 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. DISCUSSION: Although 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.

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.

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.

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.

Clinical and magnetic resonance imaging study of unilateral sideways disc displacements of the temporomandibular joint.

The aim of our study was to find symptomatic diagnostic factors for sideways displacement of the temporomandibular joint disc, compared with anterior or rotational disc displacement. A consecutive series of 2310 temporomandibular joints were examined with MRI to define the clinical signs and symptoms particularly related to sideways disc displacement compared to anterior disc displacement with logistic regression model. Bone change of the mandibular condyle and age were negatively related factors in differentiating cases with lateral disc displacement from anterior disc displacement without reduction. Range of mouth opening (over 40 mm) was a significant predictor (odds ratio 4.5865 for lateral disc displacement). This study suggested the wide opening of the mouth to become the predictor for the lateral disc displacement among the cases suspected to have disc displacement without reduction.