表面改質技術を応用し,チタン鋳造体試料を真空炉内でチタン鋳造体を変態温度以下で熱処理を行った.この処理によりチタン表面を拡散浸透固溶の傾斜機能層の形成することを目的とした.チタン材料は市販純チタン(CPチタン)およびTi-6 Al-7 Nb合金を使用して鋳造体試料を作製した.表面改質処理に伴うこれらの試料を,引張強さ,伸び,ビッカース硬さ,加熱処理時の変形量の計測,SEM像観察を行った.その結果,表面改質処理を行うことによってチタンの表面硬さは増大した.しかし,引張強さに影響は認められなかった.加熱処理によって鋳造体の変形はなかった.伸びはわずかに増大したが,処理前後における金属の種類によって伸びに有意差は認められなかった.表面SEM観察像からチタン鋳造体表層部に限局した改質が明らかであった.

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　歯科補綴治療を支える歯科技工はCAD/CAMテクノロジーの導入によって大きな変革期を迎え，歯科技工士教育の内容もこれまで以上に充実したものに変わろうとしている．歯科技工士の志願者が激減し，将来の補綴装置の製作が危機的な状況であるが，これからは高品質，高精度の補綴装置を国民に安定的に供給するためにはデジタル機器による技術と歯科技工士の高度な技能が協調し，歯科医療を支えていかなければならない．歯科技工士国家試験も念願の全国統一化がなされ，日本の歯科技工士教育はグローバルに国際的にもリーダー的役割を担うものである．

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In this study, to clarify the present state of implant-supported prostheses produced in dental laboratories, we conducted a questionnaire survey to investigate dental technicians' establishment of occlusal contact in the intercuspal position.
We surveyed special dental technicians who had attended the educational lecture at the 30th Annual Meeting of the Kinki-Hokuriku Branch of the Japanese Society of Oral Implantology, and dental technicians who were in charge of laboratory work under dental implant specialists belonging to this society. Regarding 21 investigation items, we report the results obtained from 84 dental technicians, excluding the 9 cases who omitted some items of the questionnaire. This questionnaire investigation was performed after obtaining approval from the special dental technician committee of this society.
Regarding occlusal contact in crown-bridges and dentures, 36.9% of the dental technicians answered that the condition of occlusal contact is the same in both prostheses, i.e., occlusal contact is established in the same position, and 61.3% of these dental technicians answered that the size of the area of occlusal contact is also the same. On the other hand, 61.9% of them answered that the condition of occlusal contact is not the same in both prostheses, depending on the position, area, and timing of occlusal contact, and occlusal scheme and balance in each case.
Among the dental technicians, there were differences in the area in which they established occlusal contact in implant-supported prostheses. More than half of the dental technicians answered that the area in which occlusal contact was established was the inner incline of the functional cusp when the opposing teeth were implant-supported prostheses or natural teeth. There were 15 patterns of occlusal contact area when the opposing teeth were implant-supported prostheses, and 16 patterns when the opposing teeth were natural teeth. No frequent patterns exceeding the majority in number were present, and no fixed patterns were clearly noted.
It was revealed that dental technicians in charge of implant-supported prostheses devote a considerable amount of time in coping with many implant systems. On the other hand, they commonly described no items to which they pay attention regarding prosthetic appliances including implants, showing differences in their approaches toward prosthetic appliances. These results suggest there is an urgent need to establish common goals and criteria between dentists and dental technicians.

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臨床において, 天然エナメル質に近似した組成および物理的性質を有し, 生体親和性および審美性を備えた, リン酸カルシウム系結晶化ガラスをブリッジに応用することを目的として, 平成11年4月1日から同年9月30日までに大阪歯科大学附属病院補綴咬合治療科に来院した患者30名にリン酸カルシウム系結晶化ガラス・ブリッジを装着し, 3か月間における臨床試験を行った.ブリッジはワンピースキャスト法で製作した3ユニットの固定性ブリッジとした.観察項目は支台歯の歯髄反応および二次齲蝕, ブリッジ周囲の軟組織の変化, ブリッジ自体の性状および変化, 副作用の有無について, ブリッジ装着時, 装着1週以降, 1か月以降および3か月以降において経過観察を行い, 以下の結果を得た. 1.支台歯について, 重度の歯髄反応および二次齲蝕は認められなかった. 2.ブリッジ周囲の軟組織について, 重度の炎症は認められなかった. 3.ブリッジの辺縁適合性について, ギャップが象牙質または支台築造材料に達している症例は認められなかった. 4.ブリッジの色調適合性について, 不適合で容認できない症例は認められなかった. 5.亀裂, 破折および脱落について, 亀裂および脱落は認められなかったが, 破折が装着約2週間後に1症例認められた.このブリッジの近心連結部の厚さは2.5mmと菲薄であった. 6.特記すべき副作用は認められなかった.以上の結果から, リン酸カルシウム系結晶化ガラスを用いた一歯中間欠損の3ユニットの固定性ブリッジは力学的に過酷な症例を除き, 機能性, 色調再現性, 色調安定性および生体親和性にほぼ満足のいく結果が得られ, 連結部の厚みを3mm以上確保することによって, 臨床において十分応用できると判断できた.

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Purpose: The aim of this article is to standardize the designs of zirconia copings and abutments from the viewpoint of fracture mechanics, by using a 3-D finite element method.
Materials and methods: 3-D finite element models were created in which single standing screw implants were placed in the alveolar bone, having zirconia coping crowns and zirconia abutments. Three zirconia copings were designed and designated as follows: RP0, no porcelain support; RP1, 1 mm porcelain support; RP2, 2 mm porcelain support. Similarly, three abutments were designed: RP0, having a regular diameter neck (as 4 mm implant platform); NP0, having a narrow concave curved neck; and WP0, having a wide 5 mm diameter abutment neck. Oblique static loading 100 N (30-degree buccolingal direction) was applied, and the maximum principal stress was analyzed under the different coping and abutment designed models to estimate the structural integrity of their designs.
Results: Maximum principal stress of zirconia copings was measured in RP0 as 60.2 MPa; in RP1 as 14.1 MPa; and in RP2 as 3.8 MPa. Wider porcelain support models tended to decrease principal stress. The maximum principal stress of zirconia abutments was measured in NP0 as 189 MPa;in RP0 as 94.7 MPa;and in WP0 as 91.0 MPa. The maximum principal stress in NP0 was twice that of RP0 and WP0.
Conclusion: It is suggested that a zirconia coping design having a wide porcelain support would be effective to reduce stress in the implant crown. However, a narrow concave curved neck zirconia abutment might be unfavorable from the viewpoint of fracture mechanics.

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