Tsukasa Shioyama

The effect on immunocytes of anodic oxide titanium after hydrothermal treatment.

All dental root implants come in contact with the oral epithelium, and many complex factors are found to arise in this region. In order to perform a successful dental root implantation, it is necessary to clarify the interaction of the dental root implant material with the host defense mechanisms involved in the specific and nonspecific immune responses to many antigens in oral bacteria and their components. Recently, focusing on developing the dental root implant, the Nikon Corporation improved the surface characteristics of pure titanium even further by developing a hydroxyapatite (HA) layer formed on an anodic titanium oxide film containing Ca and P via hydrothermal treatment (SA treatment). However, since little is known about the effect of SA-treated pure titanium (HA/Ti) on the defense mechanisms of the oral membrane epithelium, we investigated (1) the in vitro proliferation of murine splenic B lymphocytes on the surface of HA/Ti in the presence of three lipopolysaccharide (LPS) concentrations and (2) interleukin-1alpha (IL-1alpha) production by the reaction of human peripheral blood mononuclear cells (PBM cells) on the surface of HA/Ti under the same concentrations. After culture, murine splenic lymphocytes were measured by uptake of 3H-thymidine, and cytokine release (IL-1alpha) from PBM cells was measured by ELISA. Results showed that HA/Ti had hardly any effect on the LPS-induced proliferation of B lymphocytes and IL-1alpha production. In vitro investigations of the effects of HA/Ti on the LPS-induced proliferation of murine splenic B lymphocytes and IL-1alpha from PBM cells might be a useful way of elucidating the defense mechanism between implants and the oral epithelium.

Clinical application of dental implant with root of coated bioglass: Short-term results

During the last 4 years 73 dental implants with root-coated bioglass to replace one to three teeth in the premolar and molar sites of the mandible were inserted. The bonding ratio between implant and bone was observed clinically 1 year after implantation and installation of the superior structure. This ratio measured 52.4% to 63.3%. An acoustoelectric tester was developed that advanced our skills. The emphasis was placed on a tight fit between implant and surrounding bone.

A Case Report of a Patient Complaining of an Esthetic Problem due to Enamel Hypoplasia

症例の概要: エナメル質形成不全により審美障害を訴えて来院した14歳女子の症例を報告する.患者の祖母と父親にもエナメル質形成不全が認められた.乳歯列期にはエナメル質形成不全はみられなかったが, すべての永久歯の表面は粗で, 茶褐色を呈していた.永久歯列完成に伴い, 審美障害を改善するために当科を紹介され, 1999年1月来院した.上顎前歯部の審美障害を改善するためにラミネートベニアを装着した.下顎前歯部には, 経済的理由によりコンポジットレジン充填を行った.17カ月後, 患者の希望により下顎前歯部にラミネートベニアを装着した.3年経過したが良好な状態を維持している.考察: 年齢を考えると歯肉退縮が予想されるものの, 患者が歯の色と形態を最も気にしていることに加え, 将来, 歯肉退縮した際には治療し直すことを理解してもらったうえで, 治療計画は審美性の回復を優先した.結論: ラミネートベニアによる治療は, 審美障害を改善しただけでなく歯の色の異常に起因する劣等感をなくし, QOLの向上もはかられた.エナメル質形成不全歯に対してラミネートベニアを装着した症例報告は少ないことから, 長期間にわたる経過観察が必要である.

Breaking Strength of Dental Implant using Bioactive Glass. Stress Analysis by 3D Finite Element Method.

The purpose of this study was to clarify the mechanical characteristics of dental implants using Bioactive Glass.The value of the load bearing strength determined by the breaking strength test was used as a base to observe and analyze the implant through the 3-D Finite Element Method. These results were then compared to the analytical results from an implant model and evaluated.Results showed that fracturing of dental implants or implants coming loose was solely dependent upon where the load was applied, load angle, and direction of load application.Placement of the dental implant is determined by taking into consideration the direction of the occlusal force.The direction of load bearing in relation to occlusal contact on the outer oblique plane of the cusp and midportion of the occlusal plane was found to be desirable between 90°to 135° and 60°Cto 120°C, respectively.

Dental Implants using Bioactive Glass-Stress Analysis by the Finite Element Method. Part 2. Stress Analysis of the Superstructure.

Stress distribution depending on the material and shape of the superstructure of bioactive glass implants were analyzed by the finite element method to observe its function and stability. Focus was placed upon the effect of applying various degrees of force to different types of materials used in the coronal and body portion of the superstructure, as well as changing the width of the superstructure and observing its stress distribution.Results were as follows:1. Stress value was higher in the metal core portion of the superstructure when compared to the gold alloy.2. Stress value was highest among the gold alloy crowns.3. Stress build-up was irrelevant to coronal width when force was applied at the center of the occlusal plane.4. As force was applied continuously from the implant axis, stress build-up was observed in the shoulder or base portion of the superstructure.5. Stress build-up was affected more by force placement and direction, rather than force strength.In conclusion, applied force in the center of the occlusal plane should be at a 75°-105° angle. However if force is to be applied on the outer oblique planes of the buccal cusp, the force should be at a 105°-120° angle.

Histological Study of Dental Implants using Bioactive Glass. Bone Formation around Bioactive Glass.

Bioactive glass has been known as a material which can directly bind to bone, and the application of it to the field of dental implants has been attempted. However, few investigations on the progress of bone formation around the bioactive glass in the jaw bone have been reported.The purposes of this study were to examine the bone formation around bioactive glass, and to study the influences of the jaw bone condition on bone formation. Conditions of the jaw bone were determined according to the elapsed time between tooth extraction and implant insertion. The mandibular fourth premolars of 6 beagles were extracted, and implants were inserted into the same places at 4, 8, and 12 week intervals.In all cases, after 2 weeks a layer of newly formed bone tissue of various maturation levels were found to be in direct contact with the bioactive glass. Furthermore, bone maturation was found to be more prominent after 8 weeks. This result may suggest that bioactive glass can bind to bone without much influence from the condition of the jaw bone.