Bulletin of Tokyo Dental College最新文献

A minitracheostomy (MTS) is performed after surgery for oral cancer at our institution in patients who are at risk of postoperative airway obstruction. The aim of this study was to evaluate outcomes of preventive airway management with this procedure. A total of 105 patients undergoing preventive airway management with a Seldinger MTS kit after oral cancer surgery between October 2014 and March 2020 were enrolled. Information on patient characteristics, time required for the MTS, duration of tracheal cannula placement, and MTS-related complications was obtained from both the medical and anesthesia records. In addition, the numbers of postoperative instances of tracheotomy between April 2009 and September 2014 and extubation between October 2014 and March 2020 were also counted for a comparison. The time required for an MTS was 3.2±2.6 min. Minor complications, including mild subcutaneous or mediastinal emphysema and bleeding, were found in 5 patients, but all recovered in a short time. The median duration of tracheal cannula placement was 2 days, with a range of from 0 to 8 days. A total of 348 oral cancer surgeries were performed between April 2009 and September 2014. Among patients undergoing these procedures, 111 underwent a tracheostomy (32%), 235 extubation (68%), and 2 sustained intubation. A total of 580 oral cancer surgeries were performed between October 2014 and March 2020. Here, 121 patients underwent a tracheostomy (21%), 105 an MTS (18%), and 354 extubation (61%). The results suggest that an MTS can be performed safely and smoothly with no significant complications. They also suggest that an MTS reduces the need for a full tracheostomy and the risk of airway obstruction after extubation. We conclude that airway management strategy with an MTS is a useful option in preventing airway obstruction following oral cancer surgery.

This report describes a validation study of data in the National Database of Health Insurance Claims and Specific Health Checkups of Japan (NDB) obtained by nationwide surveys on tooth extractions. The following 3 data sources on tooth extractions in Japan were compared: (1) the Nationwide Survey of the Reasons for Permanent Tooth Extractions in Japan (a previous survey conducted by the present authors); (2) the Statistics on Medical Care Activities in Public Health Insurance; and (3) the 4th NDB Open Data Japan. Source 1 was a nationwide survey conducted in 2018; sources 2 and 3 comprised data that are freely available for use by the public. In Source 1, 2,345 of 5,250 dentists approached responded to the questionnaire (recovery rate: 44.8%). The number of extracted teeth among younger age groups (aged 25-50 years) reported in Source 1 was lower than that in the other two sources. In contrast, the number of extracted teeth among older age groups reported in Source 1 was higher than that reported in the other two sources. However, when stratified by age group, all differences across the 3 sources regarding the mean annual number of tooth extractions were <0.05 teeth/year. The present results suggest that the NDB is a reliable resource for data on tooth extractions performed across the entire Japanese population.

The objective of this study was to verify whether loss of posterior occlusal support induced displacement of the mandibular condyles from a physiological point of view. Stabilization-type splints were fabricated for 12 healthy dentulous individuals. Each splint was designed to cover the bilateral maxillary teeth up to the second molars. To reproduce loss of posterior occlusal support, the extent of the splint was reduced one tooth at a time, bilaterally, starting from the back and moving forward sequentially. Tapping movement and lateral excursions were performed with each splint and a jaw movement tracking device with 6-degrees of freedom used to observe condylar displacement. Evaluation of 3-dimensional (3-D) displacement of the kinematic axis of the condyle during experimental jaw movement was performed under each occlusal condition with occlusal contact on all teeth, including the maxillary second molars. The habitual closing position was used as the reference. An increase was observed in 3-D displacement of the kinematic axis at the terminal point of the tapping movement with loss of occlusal support, and significant differences were observed in both condyles. An increase was also observed in 3-D displacement of the kinematic axis on the working side during lateral excursion with loss of occlusal support, and a statistically significant difference was observed in the left condyle. A small increase was observed in 3-D displacement of the kinematic axis on the non-working side during lateral excursion with loss of occlusal support. The results of this study suggest that loss of posterior occlusal support induces displacement of the mandibular condyles, suggesting that occlusal support in the molar region is an important factor in stabilization of the condylar position.

Bone marrow is the principal site of hematopoiesis in mammals. Amphibians were the first phylogenetic group in vertebrates to acquire bone marrow, but the distribution of hematopoietic cells in the bone marrow of the primitive frog, Xenopus laevis (X. laevis) has not been well documented. The purpose of this study was to perform a histological investigation of the distribution of hematopoietic cells in femoral bone marrow at various stages of development in X. laevis. Hematopoietic cells showed preferential distribution on the endosteal surface of cortical bone throughout all stages of development, from tadpole to aged frog. In mature frogs, hematopoietic cells appeared at the boundary between the epiphysis and the bone marrow. The distribution of hematopoietic cells around the blood vessels was limited to a small number of vessels in the bone marrow. Abundant adipose tissue was observed in the bone marrow cavity from the tadpole stage to the mature frog stage. Hematopoietic cells showed preferential distribution in a belt-like fashion on the surface of newly-formed bones in a bone regeneration model in the diaphysis of X. laevis. These results indicate that the distribution of hematopoietic cells in bone marrow in X. laevis differs from that in mammals, and that the bone marrow of X. laevis constitutes a useful model for exploring the mechanism underlying the phylogenetic differentiation of bone marrow hematopoiesis.

Lip-seal strength is important for articulating bilabials, capturing food during eating, maintaining fluid within the oral cavity before swallowing, and achieving swallowing pressure. The objective of this study was to investigate the effect of lip-seal resistance training on lip-seal strength in young adults. The participants comprised 15 young healthy adults aged 26-34 years, all with complete dentition. Each was required to perform lip-seal resistance training 5 weekdays a week for 4 weeks with a commercially available instrument for that purpose. The instrument was placed on the midline, left corner, and right corner of the mouth, and pulled forward, leftward, and rightward, respectively. The participants were required to pull the training instrument forcefully while resisting by closing the lips together as strongly as possible until the instrument exited the lips. Lip-seal strength was measured at before and after training using a measurement device. Change in lip-seal strength between before and after training was analyzed using the Wilcoxon signed rank test. The mean lip-seal strength was 8.9±1.5 N before training and 10.4±1.8 N after. A significant difference was observed in lip-seal strength between before and after training (p=0.003), and the mean increase during the training period was 18.1±17.6%. The results showed that lip-seal resistance training for 4 weeks increased lip-seal strength in young adults. These findings suggest that training that involves pulling not only in a forward direction, but also in bilateral directions strongly stimulates the orbicularis oris muscle, resulting in an increase in lip-seal strength.

Change in soft tissue in relation to that in hard tissue following orthognathic surgery was evaluated. Twenty-five patients were enrolled in the study. The diagnosis in all was jaw deformity (maxillary retrusion and mandibular protrusion) and all underwent a Le Fort I osteotomy and bilateral sagittal splitting ramus osteotomy. Three-dimensional (3D) computer-aided design (CAD) models (polygon models) of the hard and soft tissue of the maxilla and mandible were constructed and superimposed. Reference points were established on the pre- and postoperative hard and soft tissues. Specific elements of each reference point were divided into X, Y, and Z components, respectively, and the distances in each direction and 3D distance (normal distance) measured. The Wilcoxon signed-rank test was used to determine differences in the mean values for the distance moved of each element as the error between pre- and postoperatively. The results revealed statistically significant differences in the Y-direction in the maxilla and the X- and Z-directions in the mandible. A significant difference was also observed in the 3D distances of the maxilla and mandible. Little evidence was found of linearity between the amount of hard and soft tissue movement in the X- and Z-directions in the maxilla. This means that 3D movement in the maxilla was masked more by changes in the morphology of the soft tissue than in the mandible, making it less evident. The results of this study suggest that the 3D analysis method used enables changes in hard and soft tissues to be understood qualitatively, and that it can be used in diagnosis and treatment in orthognathic surgery. It may also be useful in simulation of morphological change in soft tissue.

Aggressive periodontitis mostly affects young people, causing rapid destruction of periodontal tissue and loss of supporting alveolar bone. The destruction of periodontal tissue induces pathological tooth movement, resulting in various types of malocclusion such as crowding or spacing in the dentition. This report describes orthodontic treatment for malocclusion due to generalized aggressive periodontitis. The patient was a 31-year-old woman who presented with the chief complaint of displacement in the anterior teeth. An oral examination revealed pathological tooth mobility throughout the entire oral cavity due to severe loss of periodontal support. Many gaps in the displaced maxillary anterior teeth and crowding in the mandibular anterior teeth were also observed. The goal of subsequent treatment was to achieve ideal overjet and overbite by aligning the teeth and closing the spaces via non-extraction orthodontic treatment with stripping. The periodontal disease was managed by a periodontist who provided guidance on oral hygiene and periodontal disease control throughout the course of orthodontic treatment. Appropriate occlusion and a good oral environment were achieved. The condition of the periodontal tissue stabilized during and after orthodontic treatment, and favourable occlusal stability was observed at the 2-year follow-up examination.

One serious complication in implant surgery is displacement of the implant body into the surrounding tissue. This occurs only rarely in the mandible, however. This report describes a case of an implant body displacing into the medullary cavity of the mandible and discusses this in reference to the literature. The patient was a 72-year-old woman who was referred to our department at Tokyo Dental College Chiba Hospital (now Chiba Dental Center) by her regular dentist after an implant inserted in the left mandible in 2010 showed loosening in October 2016. Panoramic X-rays obtained at the initial examination revealed that 2 implants had been inserted into the left mandible, one on top of the other. Removal of both was recommended to prevent infection at the implant site and any potential effects on the alveolar nerve. In the absence of subjective symptoms other than implant loosening, however, the patient did not consent to this proposal. Therefore, only the broken abutment was removed. The patient was instructed to contact us immediately should infection or any other symptoms appear once the mucosa had healed, and the dental clinic that had referred her to us was requested to make her a set of dentures. To our knowledge, only 11 reports have been published to date describing displacement of an implant body into the mandible, and these address a total of just 20 cases. The possibility that an implant body in the mandible may become displaced must be kept in mind during treatment.

We report a case of generalized chronic periodontitis requiring periodontal regenerative therapy. The patient was a 53-year-old woman who presented with the chief complaint of gingival swelling. An initial examination revealed 31.5% of sites with a probing depth of ≥4 mm and 46.3% with bleeding on probing. Radiographic examination showed vertical bone resorption in tooth #33. Horizontal adsorption was also observed in other areas. Based on a clinical diagnosis of severe generalized chronic periodontitis, initial periodontal therapy consisting of plaque control, scaling and root planing, occlusal adjustment, caries treatment, and splint placement was performed. After re-evaluation, surgical periodontal treatment was performed at selected sites. Periodontal regeneration therapy with recombinant human fibroblast growth factor (rhFGF)-2 was performed at #33. Two other sites (#14, 15), which had residual periodontal pockets, were treated by open-flap debridement. After re-evaluation, the patient was placed on a maintenance program. Periodontal regenerative therapy with rhFGF-2 resulted in an improvement in angular bone resorption, which has been properly maintained for 2 years. Continued care is needed to maintain stable periodontal conditions.

While a digital arteriovenous anastomosis (Hoyer-Grosser's organ, Masson's glomus) is a well-known structure, photographic evidence of communication between arterial and venous lumens might not be demonstrated in routine histological or immunohistochemical analysis. Abundant clusters of so-called glomera were found in semi-serial sections of the distal aspect of 14 fingers obtained from 7 donated elderly cadavers. Two to six round or oval clusters were observed in each longitudinal section (over 0.3-0.6 mm in maximum diameter) in subcutaneous tissue 0.5-1.5 mm below the basal layer of the skin, whereas none were often observed in transverse sections. Lumen-to-lumen communication between arteriole and venule at 8 sites in 2 cadavers was identified in these clusters of glomera. The opening in the arteriole was large (50 μm in diameter) at 3 sites in specimens from an 80-year-old man, whereas it was small (10-30 μm) at 5 sites in those from a 91-year-old man. The arterial aspect was tightly surrounded by abundant nerve fibers expressing tyrosine hydroxylase immunoreactivity, whereas the venous part was not. No or little expression of S100 protein immunoreactivity suggested that these nerve fibers were unmyelinated. The morphology at the lumen-to-lumen communication was simple - possibly an end-to-end anastomosis - rather than a sinuous curve of arteriole opening on to a short funnel-shaped venule as seen in the standard textbooks.