Background: This study investigated the factors involving joint effusion in patients with temporomandibular disorders. Methods: The magnetic resonance images of 131 temporomandibular joints (TMJs) of patients with temporomandibular disorders were evaluated. Gender, age, disease classification, duration of manifestation, muscle pain, TMJ pain, jaw opening disturbance, disc displacement with and without reduction, deformation of the articular disc, deformation of bone, and joint effusion were investigated. Differences in the appearance of symptoms and observations were evaluated using cross-tabulation. The differences in the amounts of synovial fluid in joint effusion vs. duration of manifestation were analyzed using the Kruskal–Wallis test. Multiple logistic regression analysis was performed to analyze the factors contributing to joint effusion. Results: Manifestation duration was significantly longer when joint effusion was not recognized (p < 0.05). Arthralgia and deformation of the articular disc were related to a high risk of joint effusion (p < 0.05). Conclusions: The results of this study suggest that joint effusion recognized in magnetic resonance imaging was easily observed when the manifestation duration was short, and arthralgia and deformation of the articular disc were related to a higher risk of joint effusion.

The purpose of this study was to investigate the characteristics and the detection ability of vertical root fractures in endodontically treated teeth by intraoral radiography and cone-beam computed tomography (CBCT). CBCT images of 50 patients with root fractures in endodontically treated teeth were reviewed, and 36 vertical root fractures were taken in this study. The cause of fracture, core construction, kind of teeth, and fracture direction (bucco-lingual and mesio-distal fractures) were investigated. Detection ability of vertical root fractures by intraoral radiography and CBCT was also examined. Statistical analyses concerning the characteristics were performed by χ² test, and the detection ability was analyzed by cross-tabulation. All of the fractured teeth were nontraumatized teeth. The vertical root fracture occurrence was not differed by core construction. The vertical root fracture number was largest at the premolar teeth (p = 0.005), and the number of the bucco-lingual fracture was larger than the mesio-distal fracture (p = 0.046). Vertical root fractures were detectable using CBCT, while undetectable by intraoral radiography (p < 0.001). Vertical root fractures occurred easily in premolar teeth with bucco-lingual direction, and CBCT is an adequate radiographic method to diagnose vertical root fracture.

Purpose: A new method inducing the physiologic rest position of the mandible using the lip contact position with the closed mouth have compared with those obtained using conventional methods of placing the mandible in the physiologic rest position. Methods: The lip contact position with the closed mouth as a method was investigated whether the technique was useful for determining the occlusal vertical dimension. The relationship between the space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth and the areas of the prolabia was also investigated. Results: Median space between the maxillary and mandibular front teeth in the lip contact position with the closed mouth was 1.53 mm, a value intermediate between the value of 2.16 mm in the resting mandibular position obtained by the conventional technique and that of 1.33 mm in the swallowing position. The coefficient of variation of the space in the lip contact position with the closed mouth was significantly lower than those in the resting mandibular position and in the swallowing position. A significant positive correlation was recognized between the space in the lip contact position with the closed mouth and the area of the prolabium of the upper lip. Conclusions: These results clarified that the lip contact position with the closed mouth obtained the excellent reproducibility comparing to the conventional methods. These findings suggested that the area of the prolabium of the upper lip might offer an effective index for individual determination of the correct free-way space.

In this study, we investigated joint effusion in patients with temporomandibular disorders (TMDs) with disc displacement. The magnetic resonance (MR) images of 97 temporomandibular joints (TMJs) were evaluated, and the appearance of joint effusion was investigated. Myofascial pain and TMJ pain were considered in addition to the duration from manifestation. Disc displacement with and without reduction, as well as the region and the area of joint effusion, were investigated using the MR images. Fisher’s test was used for the analyses. Joint effusion was recognized in 70 TMJs, including 55 in the superior articular cavity, 1 in the inferior articular cavity, and 14 in both the superior and inferior articular cavities. The appearance of joint effusion did not differ with the existence of myofascial pain or TMJ pain. The region of joint effusion did not differ between disc displacement with and without reduction. A larger area of joint effusion was recognized in disc displacement without reduction (p < 0.05). The results showed that the amount of synovial fluid in the joint effusion did not change with the existence of myofascial pain or TMJ pain. Joint effusion commonly appeared in disc displacement without reduction.

We aimed to investigate the type of bone changes in temporomandibular disorder patients with disc displacement. The subjects were 117 temporomandibular joints that were diagnosed with anterior disc displacement using magnetic resonance imaging (MRI). Temporomandibular joint (TMJ) pain and opening dysfunction were examined. Disc displacement with and without reduction, joint effusion, and bone changes in the mandibular condyle were assessed on MRI. The types of bone changes were classified into erosion, flattening, osteophyte, and atrophy on the MR images. Fisher’s exact test and χ² test were performed for analyses. Bone changes were found on 30.8% of subjects with erosion, flattening, osteophyte, and atrophy types (p < 0.001). The occurrence of joint effusion appearance (p < 0.001), TMJ pain (p = 0.027), and opening dysfunction (p = 0.002) differed among the types of bone changes. Gender differences were also found among the types of bone changes (p < 0.001). The rate of disc displacement with reduction was significantly smaller than that of disc displacement without reduction on flattening and osteophyte (p < 0.001). The results made it clear that the symptoms, gender, and presence or absence of disc reduction differed among the types of bone changes.