Kokubyo Gakkai zasshi. The Journal of the Stomatological Society, Japan最新文献

Lymphoepithelial cysts occur mainly in the lateral cervical region, but rarely in the parotid gland. We report three cases of lymphoepithelial cysts arising in the parotid gland. These patients presented with a mass in the pre-auricular or infra-auricular region. All masses were mobile and non-tender. The lesions were removed by superficial partial parotidectomy. A definite diagnosis could not be made at initial evaluation, including clinical findings, ultrasound sonography, computed tomography, magnetic resonance imaging, nor radioisotope scintigraphy. Final diagnoses were made by histopathologic evaluation of the excised specimen. In these three cases, histopathologic examination of the mass showed a cystic lesion to be lined by stratified squamous or cuboidal epithelium that was surrounded by a lymphoid tissue with lymphoid follicles, leading to a histopathological diagnosis of lymphoepithelial cyst. The postoperative course was uneventful, and there has been no evidence of recurrence in any of the three cases reported. A review of 52 cases of lymphoepithelial cyst arising in the parotid gland reported in Japanese literature was also made together with the three cases of lymphoepithelial cyst arising in the parotid gland reported here. The results of this review were considered clinical presentation and histopathogenesis of the three cases of lymphoepithelial cyst arising in the parotid gland reported here.

The periodontal ligament (PDL) is a fibrous connective tissue that exists in the cementum and the alveolar bone. Periodontitis is a chronic inflammatory disease that is caused by a bacterial infection in the periodontal region. This infection increases the production of inflammatory cytokines and causes the destruction of periodontal tissue. High mobility group box 1 (HMGB1) is a nuclear nonhiston DNA-binding protein that is present in many eukaryotic cells. HMGB1 is released actively from macrophages and monocytes stimulated by lipopolysaccharide or tumor necrosis factor-alpha and passively from damaged cells and necrotic cells. Extracellular HMGB1 signals through a specialized receptor for advanced glycation end products (RAGE), toll-like receptor 2 (TLR2), and toll-like receptor 4 (TLR4). According to a recent report, HMGB1 is of concern in periodontitis. The purpose of this study was to examine the effect of HMGB1 in PDL cells. To investigate RAGE, TLR2 and TLR4 mRNA in PDL cells, reverse transcript-polymerase chain reaction experiments were performed. PDL cells were stimulated with HMGB1, with or without anti-RAGE, TLR2 and TLR4 antibodies. IL-6 and IL-11 production was measured using an enzyme-linked immunosorbent assay, and mRNA expression was quantified by real-time PCR. PDL cells expressed RAGE, TLR2 and TLR4 mRNA. Production and mRNA expression of IL-6 and IL-11 were augmented in PDL cells stimulated with HMGB1. In addition, they were also suppressed by anti-RAGE, TLR2 and TLR4 antibodies. In conclusion, PDL cells produce IL-6 and IL-11 in response to HMGB1 via RAGE, TLR2 and TLR4.

The purpose of this research was to clarify the morphological changes of the apex region of the tongue in the elderly. Apexes of tongue were removed from 44 Japanese adult cadavers (64-99 years) which were contributed for dental studies at Tokyo Medical and Dental University. These specimens were fixed again with 10% formaldehyde, and then paraffin sections were made from these specimens according to a general method. After several stainings, these sections were observed with a light microscope. The results were as follows : 1) The epithelium, propria mucosae and muscle layers became thin with aging, and the boundaries between these layers became unclear. 2) The tendencies of fibrosis also became remarkable, and the arrangement and distribution of collagen fibers and elastic fibers became disordered in propria mucosae. 3) The numbers of myocytes and myofibrils tended to decrease. 4) The connective tissue which is the outer layer of nerves tended to increase. Moreover, in some nerves, the paths of each neurofibril became tangled. 5) These findings are structural features in the apex of the tongue of the elderly, involving morphological changes of layers, fibrosis, structural changes of myocytes and myofibrils, nerves and neurofibrils in this region. These changes suggest some relationships to functional disorder in motion, pain and paresthesia of the tongue.

Calcium phosphate ceramics are widely used as bone substitutes because of their favorable biocompatibility and osteoconductivity. Some studies have reported that porous hydroxyapatite (HA), with its special structure, implanted at ectopic (non-bone) sites, exhibits osteoinductive activity. However, few studies have examined the detailed ultrastructure of mineralized tissue formed in biomaterials like HA. Therefore, it is important to examine whether the mineralized tissue exhibits structural characteristics of normal bone tissue. Thus, in this study, we subcutaneously implanted hydroxyapatite blocks (5 x 5 x 7 mm) into the backs of adult dogs, and performed detailed morphological examination of the bone-like tissue formed, which showed a lamellar structure. Immunohistochemical staining revealed that the matrix fibers of the bone-like tissue were mainly composed of type I collagen. The pattern of crystal deposition in matrix fibers and the structure of osteoblast-, osteocyte-, bone-lining-, and osteoclast-like cells were similar to those of normal bone tissue and osteogenic cells, respectively. These results indicate that cellular events observed in normal bone formation and remodeling occur in bone-like tissue as well, and suggest that bone-like tissue in HA blocks is very similar to bone tissue.

As part of morphological research to investigate the development and function of the human dentino-enamel junction, structural features of net-like structures on the decalcified dentin surface of upper and lower incisors were observed by using stereoscopic microscope, and scanning and transmission electron microscopes. The results were as follows : 1) The net-like structures on the decalcified dentin surface were stained by hematoxylin, orange G phosphomolybdic acid, toluidine blue and aniline blue. 2) The majority of net-like structures were covered with a membrane-like structure. 3) An individual reticulation of net-like structures corresponds to the margin of each dentin foveolus. 4) The dentin crystals situated in the vicinity of the dentinoenamel junction were larger than the crystals of usual dentin and were more closely aligned. On the other hand, the enamel crystals in this region were smaller than those in other layers of enamel. The surface dentin in the vicinity of the dentino-enamel junction seemed to be highly calcified. 5) It was possible to clearly demonstrate the outline and distribution of dentin foveolus by using certain dyes on the decalcified specimen. 6) By observing the distribution and structural features of net-like structures in detail by applying this dye method to human and animal teeth, the formation mechanism of the dentino-enamel junction and functions of those teeth were elucidated morphologically.

Distraction osteogenesis has been widely used even in the craniofacial region. A long fixation time during the consolidation period, however, is a major clinical disadvantage. Hyperbaric oxygen (HBO) has been used to improve healing in ischemic wounds. We have recently started applying hyperbaric oxygen to cleft palate patients after maxillary distraction, but there is little basic evidence. We hypothesized that hyperbaric oxygen would enhance the healing of distraction osteogenesis in the cleft palate model in dogs. A bony segment including a canine was transported proximally into an artificial bone defect in the left palate. Three dogs were treated with hyperbaric oxygen for 20 days just after the distraction and three other dogs underwent only the distraction process (control group). Blood flow of the canine pulp in the bone segment was monitored using a laser Doppler flowmeter throughout the experiment. All the dogs were sacrificed on day 100, and radiological analysis using peripheral quantitative CT and histomorphometric evaluations were performed. Blood flow in the HBO-treated group recovered to the original level about 30 days faster than in the control group (p<0.05). Cortical bone mineral density was significantly higher at the distraction site in the HBO-treated group than in the control group (p<0.05). The histomorphometric analysis revealed that the newly formed bone area was also larger in the HBO-treated group than in the control group (p<0.05). These results suggest that hyperbaric oxygen treatment could be useful for early removal of the distraction device in distraction osteogenesis.

BMP-12, other than BMP-2, 4, and 7, is known to induce the formation of tendon/ligament-like tissues. However, the role of the protein in the process of bone or cartilage healing has not been adequately examined. The purpose of the present study was to examine if a plasmid vector encoding BMP-12 would induce tendon/ ligament formation in a rat bone defect model. A lyophilized atelocollagen pellet with 100 microg of a plasmid vector encoding BMP-12 or BMP-2 was implanted in a bone defect of a rat femoral metaphysis. The samples were retrieved at 2, 4 and 8 weeks post-operation and subjected to histology and real-time PCR analysis. BMP-12 transgene indicated prominent fibrogenesis at 2 weeks. Consequently, the tissue was substituted by bone at 8 weeks. The gene expression of collagen type III was up-regulated by BMP-12 gene transfer after 2 weeks, followed by an increase of elastin and Six1 genes after 4 weeks. These genes, which are intimately related to tendon/ligament formation, decreased in expression at 8 weeks in preparation for osteogenesis afterward. On the other hand, the BMP-2 transgene quickly induced the synthesis of bone-related genes such as collagen type I and ALP. It is concluded that BMP-12 can initiate the development of tendon/ligament-like tissue in a rat bone defect at early healing stages. Maintaining such generation of tissue on bone could be useful for modifying periodontal tissue engineering.

The purpose of this study was to assess the influence of residual stress produced after the bending manipulation of a straight wire on flexibility and permanent deformation of wrought-wire clasps. A three-dimensional finite element model of a straight wire (12 mm in length and 1.0 mm in diameter) was created. Elastic and plastic properties of a commercial Co-Cr straight wire measured by means of tensile test were input into the program. We simulated the bending of the clasp shoulder and clasp arm to an angle of 90 degrees or 120 degrees and subsequent unloading processes with spring-back phenomenon. The maximum residual tensile stress appeared at the inside of the bending angle after unloading of the bending force. Thereafter, the clasp models were deflected 0.25, 0.50 mm, and 0.75 mm at the tip to simulate the removal and insertion of a denture. The maximum tensile stress at the inside corner of the bending angle under the deflection was considerably higher than the residual stress before deflection. The stress increase by the deflection was larger at the shoulder than the arm. The load required for deflection was larger in the models with the arm of 120 degrees angle than models with the arm of 90 degrees angle. The results suggest that the permanent deformation of wrought-wire clasps is likely to initiate at the clasp shoulder, while the clasp flexibility is dependent on the bending angle of the clasp arm.

Cementum is an essential tissue to maintain tooth function and should be closely correlated to tooth root development and periodontal tissue regeneration. However, detailed features of the periodontium including cementum and specific markers for cementoblasts are unknown. Moreover, the molecular mechanism of periodontal tissue development, homeostasis and regeneration remains unknown. Previous studies have usually examined cementum or periodontalligament (PDL) tissue obtained by manual curettage, resulting in difficulties in isolating pure cementum or PDL. We employed laser capture microdissection (LCM) to isolate cementoblasts and PDL cells from undecalcified frozen sections of murine mandible and to obtain RNA of good quality for subsequent genetic analysis. Over 500 cementoblasts and PDL cells were separately laser captured under microscopy. A bioanalyzer detected peaks of 18S and 28S rRNA both in the laser-dissected cementoblasts and in PDL cells, suggesting that the RNA was of sufficient quality. The RNA samples were amplified due to their small amount and a comparative analysis of mRNA expression by GeneChip showed that about 2,000 genes were differentially expressed between cementoblasts and PDL cells. Both cementoblast-positive and PDL cell-negative genes were serially analyzed by quantitative RT-PCR using RNA samples obtained from mandibles and femurs. Several genes were expressed at higher levels in the mandible than in the femur, suggesting that some might be cementoblast-specific markers. We established a novel experimental system with which to isolate target tissues from single cells in undecalcified frozen sections and to obtain intact RNA. These methodologies could be useful for further investigation of mineralized tissues and to explore tissue-specific factors.

The masseter-muscle spindle is regarded as being highly adaptable to increases in the occlusal vertical dimension (iOVD), it is hypothesized that spindle function would adapt to a decrease in occlusal vertical dimension (dOVD) as well. Seventy-five 5-week-old female Wistar rats were divided into Control (n = 25) and Experimental (n = 50) groups; those in the Experimental group received a 2.0-mm composite resin build-up to the maxillary molars. The Experimental group was divided into the resin-removal group (n = 25, build-up resin was removed) and the non resin-removal group (n = 25) 8 weeks later; i. e., when the animals were 13 weeks old. Electrophysiological recordings were obtained from masseter-muscle spindle afferents in 13, 14, 15, 19, 21-week-old rats (n = 5 rats each) under general anesthesia Masseter-muscle spindle sensitivity was significantly lower in the resin-removal group 1 week after resin-removal and for the rest of the observation period. The present results indicate that masseter-muscle spindles may not completely adapt to dOVD and may affect jaw function.