The effects of mandibular distraction on the mandible and its surrounding tissue remain to be clarified. Here, we used a 3-dimensional finite-element method to investigate the effects of unilateral horizontal lengthening of the mandibular body and vertical lengthening of the mandibular ramus on the mandible and temporomandibular joint (TMJ). With horizontal loading that assumed mandibular body lengthening, tensile and compressive stresses were great near the anterior region of the mandibular angle (the loading area). With vertical loading that assumed mandibular ramus lengthening, tensile and compressive stresses were great at the center of the mandibular ramus (the loading area). Under both loading conditions, stress distribution in the TMJ was greater on the loading side than on the non-loading side. With mandibular body lengthening, the center of the mandible deviated in the direction of the non-lengthened side to widen the mandible in the lateral direction. With mandibular ramus lengthening, the occlusal plane tilted in the inferior direction on the lengthened side. In the TMJ, stress was greatest on the affected side during mandibular ramus lengthening, suggesting the need to consider the mandibular condyle on the affected side during this procedure.

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We focused on brain areas activated by audiovisual stimuli related to swallowing motions. In this study, three kinds of stimuli related to human swallowing movement (auditory stimuli alone, visual stimuli alone, or audiovisual stimuli) were presented to the subjects, and activated brain areas were measured using fMRI and analyzed. When auditory stimuli alone were presented, the supplementary motor area was activated. When visual stimuli alone were presented, the premotor and primary motor areas of the left and right hemispheres and prefrontal area of the left hemisphere were activated. When audiovisual stimuli were presented, the prefrontal and premotor areas of the left and right hemispheres were activated. Activation of Broca's area, which would have been characteristic of mirror neuron system activation on presentation of motion images, was not observed; however, activation of brain areas related to swallowing motion programming and performance was verified for auditory, visual and audiovisual stimuli related to swallowing motion. These results suggest that audiovisual stimuli related to swallowing motion could be applied to the treatment of patients with dysphagia.

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This study investigated the influence of different composite resin shades on light energy transmission through the composite, hardness and cross-link density (CLD). The composite Filtek Z250 was used in shades A1, A2, A3, A3.5 and A4. A quartz tungsten halogen light curing unit was used at an irradiance of 900mW/cm². Thirty specimens were made for each shade. Light energy transmission that passed through the composite was calculated (n=10). Differences in Knoop hardness between the top and bottom (DKH) of the same specimen were calculated (n=10). The Knoop hardness value for each surface was recorded as the average of three indentations (KHN₁). Thereafter, the specimens were soaked in absolute ethanol for 24hr at room temperature, and hardness was again determined (KHN₂). The CLD was estimated by the softening effect produced by ethanol, i.e., by decrease in hardness. The percentage of decrease in KHN₂ compared with KHN₁ (PD) in the same specimen was then calculated for both surfaces (n=10). The data were submitted to an ANOVA in different tests (Light energy transmission, Knoop hardness and CLD). The irradiance of light that passed through composite shade A1 (408mW/cm²) was statistically greater than that through shade A2 (376mW/cm²), and was greater through A2 than A3 (359mW/cm²) and through A3 than A3.5 (327mW/cm²); A3.5 showed no statistical difference when compared to A4 (324mW/cm²). The DKH of A4 (20.56%) was not statistically higher than that of A3.5 (20.14%), which was greater than that of A3 (14.08%), A2 (11.65%) and A1 (9.06%). There was no statistical difference in CLD. Darker shades had a significant influence on light energy transmission through dental resin composite and its hardness. However, CLD was not affected by darker dental composite shades.

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The purpose of this study was to investigate the influence of anteroposterior postural change on electromyography (EMG) activity in the lateral pterygoid muscle. Subjects consisted of 7 patients attending this hospital for close examination. The inferior heads of the lateral pterygoid and masseter muscles were chosen as evaluation sites. For the EMG recordings, the test movement was opening and closing of the mouth; postural conditions were the upright and supine positions. The mean value of EMG activity in the inferior head of the lateral pterygoid muscle was calculated. During mouth-opening in 5 out of the 7 patients, and during mouth-closing in 2 out of the 7 patients, mean value of EMG activity differed significantly with body position. Mean value of EMG activity was reduced in the supine position. The results revealed that anteroposterior postural change affected mean value of EMG activity in this muscle.

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A case report is presented on transplantation of a left third molar to replace a right second molar lost due to large furcation perforation. Two weeks after surgery, a reentry surgical procedure was performed on the furcation defect of the second molar to remove membrane and retrieve proliferating periodontal tissue. The left third molar and proliferating periodontal tissue were then transplanted into the bone defect of the right second molar. Radiographically, the transplanted tooth showed no root resorption over a 3-year period. The results indicate that teeth replanted with proliferating periodontal tissue have a favorable long-term prognosis.

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Number of patients assigned to dental residents, course of treatment and number of various technical tasks performed as described in the Reports on Clinical Training of Dentists published by the Department of General Dentistry, Tokyo Dental College Chiba Hospital since its establishment in 2002 were compared between before (2003-2005) and after (2006-2007) clinical training was made mandatory, and the state of clinical residency evaluated. Number of patients assigned generally increased, and mean number of patients treated by each resident in 2007 (15.08) was approximately 2 times higher than that in 2003 (8.47). Total number of treatments was 1.38 times higher in 2007 than in 2003, and periodontal treatment accounted for approximately 40% of all treatment both before and after clinical training became mandatory. Number of technical tasks in 2004-2007 was less than half the peak in 2003. To further improve clinical training, evaluation and implementation of effective approaches is necessary to secure an adequate number of patients, widen the variety of cases and increase the number of technical tasks.

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