Noriyuki Hisamori

Metal ions induce bone-resorbing cytokine production through the redox pathway in synoviocytes and bone marrow macrophages.

To evaluate the biological reactions to metal ions potentially released from prosthetic implants, we examined the ability of metal ions to produce bone-resorbing cytokines and the underlying mechanism using synoviocytes and bone marrow (BM) macrophages. The cells were incubated with NiCl(2), CoCl(2), CrCl(3) or Fe(2)(SO(4))(3) at optimal concentrations, which are detectable in joint fluid following total joint arthroplasty. The production of interleukin-1beta, interleukin-6 and tumor necrosis factor-alpha were enhanced by all metal ions tested as determined by enzyme-linked immunosorbent assay. From the results of electrophoresis mobility shift assay, all metal ions enhanced the DNA-binding activity of nuclear factor kappaB (NF-kappaB), and p50-p65 heterodimers and p50 homodimers were the major subunits. These effects of the metal ions were considerably blocked by pyrrolidine dithiocarbamate (PDTC) known as a radical scavenger. An electron spin resonance study clearly demonstrated the ability of metal ions to generate activated oxygen species (AOS), especially hydroxyl radicals (*OH), which accounts for PDTC-blockade of metal ion-induced NF-kappaB activation and subsequent cytokine production. Taken together, our data raised the possibility that small amounts of metal ions released from prosthetic implants activate synoviocytes and BM macrophages through the AOS-mediated process (i.e. the redox pathway), and contribute to the initiation of osteolysis at the bone-implant interface.

Adhesive Strength of Bioactive Surface Layer

Bioactive capability of Ti-alloy for implant application has been developed by producing thin hydroxyapatite (HAp) film on its surface. The adhesive strength between the base metal and the HAp film has to be evaluated to ensure the reliability of the implant. But the method of evaluation is not yet established because of its difficulty to cause adhesive fracture between base metal and HAp thin film. In this chapter, tensile load is applied to the HAp film on Ti-6Al-4V alloy substrate normal to its thickness by using a specimen bonded with adhesives. Surfactant is applied near the interface between Ti-6Al-4V substrate and HAp film by adhesives to avoid coverage of the interface. Thus the accuracy of this method is improved by preventing adhesive overflow from bonded surface to the side of the specimen. As a result, fracture occurs at interface between Ti-alloy and the HAp film. This method is proved to be useful for evaluating bond strength between Ti-alloy and HAp film and verifying the fracture of the adhesive layer.

The 22rd and 23th Fatigue Design Short Courses for Beginners

1. はじめに 各種機械製品の破損事故の多くは,繰返し応力負荷に より発生する「疲労現象」を原因としています.そのた め,製品の設計および保守に携わる技術者にとって,疲 労破壊の防止や寿命予測は重要です.一方,近年の社会 的状況下では,疲労に係る知識および技術伝承は必ずし も容易ではありません. 以上を背景として,疲労部門委員会では2日に渡る「初 心者のための疲労設計講習会」を開催しています.以前 は毎年1回の開催でしたが,最近は受講希望者からのご 要望もあり,関東および関西両地区等で毎年2回以上開 催しています. 本講習会は,疲労に係る問題を抱えている技術者だけ でなく,若手研究者や工学系学生をも対象としています. 講習会では,事故事例の紹介から始まり,基礎知識全般 を習得してもらった後,実際の疲労設計法について説明 されます.各講習日の最後には,理解を深めてもらうた めに演習を実施しています.具体的な講義内容は下記の 通りです. 1. 疲労現象と事故事例 2. 疲労強度I:S-N曲線,切欠きの影響,寸法効果 3. 疲労強度II:平均応力および残留応力の影響,低 サイクル疲労 4. 疲労き裂進展:破壊力学の基礎,疲労き裂の進展 挙動および影響因子 5. 実働応力下の疲労:線形累積損傷則,ランダム荷重 6. 疲労強度設計I:疲労強度設計および疲労寿命設 計の概論,溶接構造物の設計規格 7. 疲労強度設計II:鉄道車軸および台車枠の設計法 8. 疲労強度設計III:原子力機器の設計指針 9. 演習 受講者には疲労部門委員会より修了証が発行されま す.また,本講習会の受講は日本材料学会技能検定・ 材料試験士 1級(疲労試験)の受験条件となっていま す. 2. 第22回講習会 第22回の講習会は,本年9月1日~ 2日に大阪工業大 学うめきたナレッジセンター(グランフロント大阪ナ レッジキャピタルタワー C9階)で開催されました.定 員40名のところ,受講者は40名と満杯でした.受講者 の皆さんは,熱心に講義を聞かれておりました(図1). また,講義の合間には多数の受講者が,講習内容だけで なく,個別の案件について講師の先生に質問されていま した. 3. 第23回講習会 第23回の講習会は,本年9月4日~ 5日に中央大学後 楽園キャンパスで開催されました.受講者は18名で, 全員が企業の方でした.このことからも本講習会が社会 的に必要とされていることがわかります.第23回の講 習会でも,講義の合間に多数の受講者が講師の先生に質 問されていました. 4. おわりに 初心者のための疲労設計講習会は,今後も引き続き開 催を予定しています.関西地区での次回講習会は,本学 会主催による「材料WEEK」が来年10月中旬に京都で 開催されるため,その期間中に実施される予定です.皆 様,是非参加してスキルアップを図って下さい.なお, 講習会で使用されているテキストは,「初心者のための 疲労設計法」(ISBN4-90138125-3)として発行されてい ます.社内勉強会や講義等にどうぞご活用下さい. 第 22回・23回初心者のための疲労設計講習会 † 森 田 辰 郎* 久 森 紀 之**

Corrosion Wear Characteristics of ELID-Ground Co-Cr Alloy with Applying Abrasion by Ultra High Molecular Weight Polyethylene (UHMWPE)

The purpose of this paper is to evaluate the surface properties and corrosion behavior of Co-Cr alloys ground by employing Electrolytic In-process Dressing (ELID) grinding; this evaluation was carried out by abrading the alloy surfaces using ultra high molecular weight polyethylene (UHMWPE). The evaluation results showed that ELID grinding can be used to perform mirror finishing on Co-Cr alloys. ELID grinding also showed its ability to create a stable modified layer which improves corrosion wear characteristics on the workpiece surface.

Development of Bone-Like Composite Material and its Properties

Many kinds of materials are currently used as artificial bone substitutes. Hydroxyapatite (HA), the same as the main inorganic component of bone, is one of commonly used bio-ceramics and has excellent bioactivity and biocompatibility with hard tissues. However, it has problems as the bone filler or bone tissue-engineering scaffold due to low fracture toughness and low degradation rate. Recently, biodegradable materials for bone tissue have been developed to respond the requirement. Collagen, the same as the main organic component of bone, is biocompatible, biodegradable and promotes cell adhesion. A composites associated with HA is expected to have early osteoconduction and bone replacement ability. The present study was to fabricate bone-like composites consist of HA and collagen. Besides the ossiferous ability of the material in vivo is evaluated by using rabbits. Bone-like composites were successfully fabricated in this study, associating the collagen with HA. And the composites presented good osteoconductive and bone replacement potential.

FABRICATION OF BONE LIKE COMPOSITES MATERIAL AND EVALUATION OF ITS OSSIFEROUS ABILITY

Many kinds of materials are currently used as artificial bone substitutes. Hydroxyapatite (HA), the same as the main inorganic component of bone, is one of commonly used bio-ceramics and has excellent bioactivity and biocompatibility with hard tissues. However, it has problems as the bone filler or bone tissue-engineering scaffold due to low fracture toughness and low degradation rate. Recently, biodegradable materials for bone tissue have been developed to respond the requirement. Collagen, the same as the main organic component of bone, is biocompatible, biodegradable and promotes cell adhesion. A composites associated with HA is expected to have early osteoconduction and bone replacement ability. The present study was to fabricate bone-like composites consist of HA and collagen. Besides the ossiferous ability of the material in vivo is evaluated by using rabbits. Bone-like composites were successfully fabricated in this study, associating the collagen with HA. And the composites presented good osteoconductive and bone replacement potential.