Hideki Saka

Age estimation based on three-dimensional measurement of mandibular central incisors in Japanese

The purpose of this study was to investigate an age estimation method that considers gender as well as three-dimensional measurement of the components, specifically enamel and dentin. A total of 155 mandibular central incisors aged 12-79 years old which was chosen from the collection stored at the Department of Anatomy in Tokyo Dental College and had no opened apex, caries or restorative treatment, were examined. Samples were scanned using micro-CT HMX225 ACTIS4. Based on the sliced image data, three-dimensional structures were obtained and the volumes of enamel, dentin, and pulp cavity were measured. Regression equations for age estimation were then determined. The accuracy of age estimation equations for each region, volume ratio, and sex was assessed using the determination coefficient R(2) as well as the standard errors of estimated values. The root region alone had a comparable accuracy to that of the whole tooth and the crown region had a relatively lower accuracy. In the whole tooth and the crown region, slightly higher correlations were observed for pulp/tooth volume ratios in which enamel was excluded. Females tended to have higher accuracy compared to males. The estimated age was higher in males compared to females for the same volume ratio of the pulp cavity. The highest correlation in both genders with age was observed for the volume ratio of the pulp cavity to the whole tooth excluding the enamel (males, R(2)=0.67; females, R(2)=0.76). The 95% confidence intervals for the population regression showed different distributions for each sex. In the 95% prediction intervals for age estimation, females tended to have narrower intervals and higher accuracy compared to males. Therefore, the use of gender-specific equations is recommended for age estimation.

Expression of Myostatin and Follistatin in Mdx Mice, an Animal Model for Muscular Dystrophy

Follistatin is a functional antagonist of several members of the TGF-&bgr; family of secreted signaling factors, including myostatin, the most powerful inhibitor of muscle growth characterized to date. Myostatin inhibition offers a novel therapeutic strategy for muscular dystrophy by restoring skeletal muscle mass and suppressing the progression of muscle degeneration. To assess the potential benefits of follistatin in treating muscle degenerative diseases, we examined the expression of myostatin and follistatin in Mdx mice, a model for Duchenne muscular dystrophy, and in B10 mice as a control. Our results demonstrated a temporary and coincident expression of follistatin and myostatin in both mouse strains, but this expression was significantly higher in Mdx mice than in B10 mice. The maximum expression of follistatin and myostatin in the presence of restoring necrotic muscle was detected 4 weeks after birth in Mdx mice. Interestingly, during the stage of complete regeneration, the absence of myostatin and follistatin proteins and a marked decrease in the expression of both genes were observed 9 weeks after birth in both mouse strains. These findings suggest that follistatin not only blocks myostatin but also allows other activators to function in muscle development, emphasizing that follistatin could be a very potent molecule in combating muscle loss during dystrophies and muscle ageing, disuse, or denervation.

Three-Dimensional Analysis of the Internal Structure of the Mandibular Condyle in Dentulous and Edentulous Jaws Using Micro-CT

Abstract This study clarifies the internal structure of the mandibular condyle in dentulous and edentulous jaws; three-dimensional observation and morphological measurements were performed using micro-CT. The materials used in this study were 14 mandibular condyles each removed from the dentulous and edentulous cadavers. Internal structures of the mandibular condyle were morphologically analyzed in three anatomical planes. Additionally, morphometrical observations of the trabecular bone structure at five regions of interest and cortical bone thickness were performed. The mandibular condyle of dentulous jaws consisted predominantly of regularly aligned plate-shaped trabeculae. Conversely, edentulous jaws were predominantly irregularly aligned narrow rod-shaped trabeculae. The results of morphometrical analysis showed that trabecular separation (Tb.Sp) in the central region of the mandibular condyle most closely reflected the difference between dentulous and edentulous jaws. These results suggest that, in edentulous jaws, reduced masticatory function due to tooth loss affects the internal structures of mandibular condyle.

Increased expression of decorin during the regeneration stage of mdx mouse

Satellite cells exist in postnatal muscle tissue and constitute the main source of muscle precursor cells for growth and repair. These cells carry out important roles for skeletal muscle formation postnatally during growth of muscle mass as well as damage-induced regenerative processes. Muscle regeneration supports muscle function in aging and has a role in the functional impairment caused by progressive neuromuscular diseases. Major substances controlling this process are growth factors and extracellular matrix. Myostatin, a member of TGF-β family, was mainly expressed in muscle tissue. Decorin, a member of the small leucine-rich proteoglycan gene family, is composed of a core protein and a dermatan/chondroitin sulfate chain. Recent studies have shown that decorin enhanced the proliferation and differentiation of myogenic cells by suppressing myostatin activity. Thus, decorin appears to be a new molecule in the myostatin signaling pathway and a promising target for treatment of progressive neuromuscular diseases. Therefore, in this study, we examined the localization of decorin as well as myostatin in a muscular dystrophy model in mdx mice and B10 Scott Snells mice as a control to elucidate the differences between decorin and myostatin messages as well as protein distribution. This study revealed increased expression of decorin protein as well as mRNA at the regenerative stage of mdx mice compared to early stages, while only weak expression of decorin was detected in the control mice. Our study contributes to identifying the relationship between decorin and myostatin as well as the development of a therapeutic strategy for progressive neuromuscular diseases.

Fetal anatomy of the upper pharyngeal muscles with special reference to the nerve supply: is it an enteric plexus or simply an intramuscular nerve?

We examined pharyngeal nerve courses in paraffin-embedded sagittal sections from 10 human fetuses, at 25-35 weeks of gestation, by using S100 protein immunohistochemical analysis. After diverging from the glossopharyngeal and vagus nerves at the level of the hyoid bone, the pharyngeal nerves entered the constrictor pharyngis medius muscle, then turned upward and ran superiorly and medially through the constrictor pharyngis superior muscle, to reach either the levator veli palatini muscle or the palatopharyngeus muscle. None of the nerves showed a tendency to run along the posterior surface of the pharyngeal muscles. Therefore, the pharyngeal nerve plexus in adults may become established by exposure of the fetal intramuscular nerves to the posterior aspect of the pharyngeal wall because of muscle degeneration and the subsequent rearrangement of the topographical relationship between the muscles that occurs after birth.

Root resorption of maxillary primary incisors in relation to position of successive permanent incisors by Micro-CT

The aim of this study is to elucidate the root resorption of primary incisors in relation to the development of permanent incisors. We observed the maxillas of the dry skulls of Indian children, using Micro-CT, and measured distance between the root surface of the primary incisor and the bony crypt of the permanent incisor. The bony crypt of the maxillary permanent incisor, which was situated at the lingual side of the primary incisor, grew upward towards the mouth as the tooth eruption stage proceeded. Root resorption was clearly seen at the primary dentition stage, and it proceeded to from root surface towards root canal at the first molar eruption. With the advance of the stage, the distance between the root surface of the primary incisor and the bony crypt of the permanent incisor became shorter, especially the distance between the root of the primary lateral incisor and the bony crypt of the permanent central incisor did. By using Micro-CT, we could confirm more clearly that the growth of the bony crypt of the central permanent incisor deeply influence the progress of root resorption of the primary lateral incisor.

Three-dimensional analysis of pulp chambers in mandibular first deciduous molars

Abstract In crown restoration, it is important to understand the internal anatomical feature of each tooth, as the morphology of human deciduous teeth is particularly complex. The purpose of this study was to clarify threedimensionally the topographic relationship between the crown contour and the pulp chamber of the mandibular first deciduous molars using a micro-CT system. Fifteen mandibular first deciduous molars obtained from the dried skulls of Indian children in the deciduous dentition period were used as specimens. Three-dimensional reconstructed images were reproduced by combining the two-dimensional slice imaging data using a micro-CT system. Crown contours and shapes of the pulp chamber were observed from various directions. In addition, the thickness of tooth substance at each pulp horn was also measured. In observations of the topographic relationship between the crown contour and the pulp chamber, the pulp horn of the mesiobuccal pulp chamber was found to project the most to the cusp side. The distance between the pulp horn and enamel surface was also shortest (2.45±0.30mm) in this region. Furthermore, in teeth with a deep, wide trigonid notch, the lateral wall of the mesiobuccal pulp chamber projected in the mesial direction. These results suggest that in preparation of cavities in mandibular first deciduous molars, close attention must be focused on pulp exposure in the pulp horn of the mesiobuccal pulp chamber. In addition, the lateral wall of the mesiobuccal pulp chamber should be noted in teeth with the deep, wide trigonid notch.

The morphological studies of root resorption of maxillary primary canines and their relation with the position of successive permanent teeth using Micro-CT

The purpose of this study is to clarify the root resorption of maxillary primary canines in relation to the development of successive permanent teeth. It was observed the maxilla of dry skulls of Indian children, using Micro-CT, and measured shortest distance between the root surface of maxillary primary canine and the bony crypt of maxillary canine. The bony crypt including successive canine was positioned almost directly above the root of primary canine and located superior to another bony crypts in the primary dentition stage. When the first molars reached the alveolar crest in addition to the primary dentition stage, the bony crypt of canine grew, showing the distal inclination of the superior margin and mesial inclination of the inferior margin. After the stage which is central incisors reached the alveolar crest, root resorption of primary canines was observed on the lingual side nearby the root apex and the bony crypt of canine was adjacent to the nasal cavity. It was quantitatively shown that the distance between the roots of primary maxillary canine and canine bony crypts reduced from central incisors reached the alveolar crest to lateral incisors reached that.

Three-dimensional observation of internal structure in the region of mandibular deciduous canine using Micro-CT

Abstract The objective of this study is to clarify the changes in the internal structure of the surrounding area in deciduous canine and in relation to the development of successive permanent teeth. We observed the mandibles of the dry skulls of Indian children, using Micro-CT, and measured height of the compact bone at the mandibular base. When the first molars reached the occlusal line in addition to the deciduous dentition stage, the superoinferior position of canine bony crypt located lower than that of other permanent teeth. After this eruption stage, the bony crypts of canine showed inferior growth, resulting in compact substances resorption of the mandibular base. When the central and lateral incisors reached the occlusal line, resorption of compact substance was advanced, but adjunction was observed after deciduous canine shed. Trabecular bone appeared for some directions in the region of sponge bone. The height of compact bone at the mandibular base was measured to elucidate the changes of the compact substance inside of the mandibular base with advancement of the dental eruption stage. The result of measurements quantitatively showed that the bone resorption advanced to the state of central and lateral incisors reached the occlusal line and adjunction occurred after deciduous canine shed.