The wear performances of bovine tooth enamel (BTE) against translucent tetragonal zirconia polycrystals (TZP) compared to that of feldspar porcelain and the influence of surface treatments of translucent TZP were investigated by the two-body wear test. Translucent TZP and feldspar porcelain were used as hemisphere abrader specimens with a radius of curvature of 5 mm; flat BTE surfaces were used as substrate specimens. The cross-sectional area of the worn surfaces of the substrates and the wear volume of the antagonist abraders were measured. Surface roughness, hardness and coefficient of friction as well as SEM observations and EPMA analyses were also performed to investigate the underlying mechanism of wear. The results suggested that BTE is less susceptible to wear when translucent TZP is used as the antagonist in contrast to the use of feldspar porcelain, and that surface treatment of the TZP abraders significantly influenced the wear of BTE substrates.

This study investigated the influence of surface roughness and cyclic loading on fatigue resistance in Y-TZP subjected to hot isostatic pressing (HIP). Fifty Y-TZP cylinders 3.0 mm in diameter were divided into Group A (polished by centerless method; TZP-CP) or Group B (blasted and acid-etched: TZP-SB150E). Twenty five cp-titanium cylinders (Ti-SB150E) were used as a control. Static and cyclic tests were carried out according to ISO 14801. The cyclic fatigue test was performed in distilled water at 37°C. Surface morphology and roughness as well as crystal phase on the surfaces were also evaluated. Fracture force under the static test was 1,765N (TZP-CP), 1,220N (TZP-SB150E), and 850 N (yield force, Ti-SB150E). Fracture values under the cyclic test decreased to approximately 70% of those under the static tests. These results indicate that HIPed Y-TZP with a 3.0-mm diameter has sufficient durability for application to dental implants.

顎 運 動 に 関 す る 研 究 は，1984 年 に Lundeen と Gibbs 1) が，咀嚼運動や咬合接触点を再現するために 顎運動測定器を開発し，研究報告されてきた．日本で も種々の顎運動測定器を用いて運動解析した多くの研 究が報告されている 2-5) が，それらは数値化するにと どまり，顎運動を様々な角度からビジュアル化して 3 次元表示することはできなかった．現在では，口腔内 スキャナや CAD/CAM スキャナから読み取ったスタ Purpose: The purpose of this study was to reproduce three-dimensional chewing movements and the change of occlusal contact points by software. Materials and Methods:The study model was converted into the software as STL data from a CAD scanner. In addition, we recorded XML data of the mandibular border movement, opening and closing movements, and chewing movements using a six-degree-of-freedom jaw tracking device (ARCUS digma2, KaVo, Biberach, Germany). The XML data was converted to STL data, and we reproduced the three-dimensional chewing movements and occlusal contact points by the software. Discussion: Using the functional analysis program, it is possible to reproduce the border movements, opening and closing movements, and chewing movements in three dimensions. We could also observe the change of occlusal contact points in the chewing movements. We suggest that occlusal interference could be found or the temporo-mandibular joint could be examined in the future by using the software to analyze three-dimensional jaw movements. Conclusions:We succeeded in observing three-dimensional jaw movements from every angle by the software. In addition, the changes of occlusal contact points in chewing movements were reproduced.