The Histological Consideration on the Interface of Dental Implants-Bone

Several qualities of materials are being used in implants. The biomaterial of the implants are usually classified as either non-bioactive or bioactive. Several studies have compared the interface of bone and different biomaterials. However, differences between the types of bone bonding, osseointegration, and contact osteogenesis have not been clarified. Formerly, titanium blade-vent implants were used for endosteal implants for a long time. Recently, various other forms and materials have been introduced for this purposes. The histological findings of these interface are also discussed in this introduction. The first cellular reaction occurs on the implant surface 1 to 3 weeks after implantation. Mononuclear phagocytes occur on the bone surface of the surrounding implant in this period. Preosteoblast and osteoblast are situated a distance of 30-50μm away from the implant surface. After 3 months, osteoblasts have reached the implant surface and bone formation is seen. The concept of osseointegration was originally introduced by Bränemark to describe the type of fibrous connective tissue-free anchorage of endosteal implant. Osseointegration is represented as healed bone in direct contact with a loaded implant surface. In the early period, movements of the implant encourage the formation of fibrous connective tissue at the implant interface. The loaded Ti-Ni Shape Memory alloy implant has been shown to come in direct contact with the bone, similar to osseointegration conditions. The hydroxyapatite coated implants (Sumicikon^[○!R]) designed by M.Ito and K. Suzuki in 1981, overcame the inter facial difficulty. The absence of fibrous encapsulation reaction allowing bonding between hydroxyapatite coating layer and the newly formed bone is an interesting phenomenon. The hydroxyapatite coated layer and the healing bone appeared to bind chemically at the interface

Histological Study of Gubernacular Cord

It has been discussed by several authors that the relationship between the gubernacular cord and the eruption of permanent teeth at the period of changing dentition. However, the roles of the gubernacular cord at this period were not yet clear. In the present study, mandibular bones of 25 young dogs were used to make clear these subjects by radiograghy, chiefly by light microscopy and electron microscopy. The gubernacular cord consisted mainly of connective tissues, which stretched from dental follicles of the permanent teeth to lamina propria of gingiva. The bundles of fibrous connective tissues, occured from the dental follicles, were observed to reach to the central region of gubernacular cord. In the outer region of the gubernacular cord, facing to the surface of the bony crypt walls, there were loose connctive tissues abounded with blood vesseles. Furthermore, mumerous osteoclasts were detected on the surface of the bony crypt walls. The results of these morphological observations may suggest that the gubernacular cord have an influence on erupting teeth, and its influence varies according to the regions of the gubernacular cord. The central region of the gubernacular cord may have a function in migrating and erupting of the permanent teeth. And the outer region of the gubernacular cord may have a function in enlarging eruption pathway of the successional teeth by resorptions of bones and roots of deciduous teeth

Monitoring of alien rats on Minami-Iwo-To Island, the Volcano Islands in 2017

南硫黄島の外来ネズミ類の侵入確認するため、センサーカメラを海岸部～頂上部に計10台を設置した。海岸林においては最大1年間、コルおよび頂上部においては3～5日間の撮影期間であったが、ネズミ類の撮影は見られなかった。また、踏査ルート上でネズミ類(生体・死体)及び痕跡(タコノキ果実への食痕等)は観察されなかった。現時点においては、南硫黄島における外来ネズミ類の侵入している可能性は低いと考えられる。Ten trail cameras were set along a survey route to confirm the absence of alien rats on Minami-Iwo-To Island. The operation periods of the cameras were 11 to 363 days in seashore forests, three days at the col, and five days at the summit. No photographs of alien rats were obtained. In addition, no traces of rats, such as live rats, dead bodies, or remnants of consumed seeds, were observed at any of the four monitored plots. It is highly probable that there are currently no alien rats on Minami-Iwo-To

Observation on the Fibers of the Periodontal Ligament during the Tooth Eruption

Recently, it is considered that the development of the periodontal ligament relates to the tooth eruption. But these relations are not yet properly understood. In this paper the periodontal ligament of the young dog was observed under the scanning electron microscope and light microscope. Specimens for SEM were fixed with 10% formaldehyde solution and sliced according to the toothaxis. After dehydration, they were dried by the critical point drying apparatus and coated with gold by using ion spattering apparatus. Periodontal ligament apparatus started to form before emergence of tooth into the oral cavity. Before eruption, the tooth germs were enclosed in a bony crypt. The developing periodontal ligament appeared to consist of loose fibers connective tissue. Fibers which subsequently became dentogingival fibers were demonstrable as an organized entity as they coursed coronally, following the outline of the crown. Apically, fibers arising from beneath the tooth, coursed into the periodontal ligament. They were oriented parallel to the long axis of the tooth. Principal fibers seemed to emanate from cementum and the bone surface. These fibers extended from the root and bone surfaces to the intermediate zone. An intermediate plexus was apparent during the tooth eruption but could not observe in the functional stage. It was considered that the fiber bundle provided the force for eruption by pulling the tooth out from the bony crypt or alveolar socket

Study on the Rigid Zone of Reinforced Concrete Frames under Horizontal Loading

The purpose of this paper is to clarify the rigid zone lengths for reinforced concrete members. The rigid zone lengths were calculated from the results of finite element analysis of column -beam connections. The equations to estimate a rigid zone lengths were derived to utilize those rigid zone lengths. The estimated rigid zone lengths were applied to three spans，1-9 stories reinforced concrete frames，and those frames were analized by stiffness method. The results of the analysis were very much in agreement with the results of finite elementanalysis of those frames

Experimental Study on Bending Strength of Four Pile Caps

In this paper seventy-four reinforced concrete pile caps, each with four piles were tested under vertical load. The variables involved were spacing of piles, arrangement of reinforcement, side length column and depth of pile cap. For all pile caps final failure was in bending. In regard to the ultimate bending strength the results of the test were compared with the values calculated according to the provision for the bending in A.I.J Building Code Requirements for Reinforced Concrete (1982), to the equations proposed by others and to that by authors. To conclude the discussions the calculated values according to the author’s equation agreed well with the experimental results

Is SPT Effective on Learning English Grammar?

　There are many studies dealing with memory. Memory encoding tasks that involve performing actions are called SPTs (Subject Performed Tasks), while tasks encoding memory without actions are called VTs (Verbal Tasks). Previous studies have reported that the score of recall tests from SPTs is higher than that from VTs when encoding verbal phrases. This effect is known as the SPT effect. Although the SPT effect is documented in many studies, the reason behind it has not been understood. This report discusses SPTs, the theories supporting SPT effects, and the possibility of learning English grammar with the help of SPTs