4-Methacryloxyethyl trimelliate anhydrite (4-META) had been reported to be a suitable monomer which promotes adhesiveness of PMMA rods with tooth substrates and dental gold alloys.
Film thickness, tensile adhesive strength and solubility of a new adhesive resin cement including 4-META were measured after cementing full coverage crown on an abutment tooth, and the values were compared with those of zinc phosphate, polycarboxylate, glass ionomer, epoxylite resin, reinforced zinc oxide eugenol cements.
The results were as follows:
1) The film thickness of the adhesive resin cement on the margin was about 75 μm as cast, but it was reduced to 26 μm by adding vent of internal groove.
2) Force required to dislodge crown cemented by the adhesive resin cement was about 100kg.
3) Force required for separation of the cement resin crown-tooth assemblies was about 26kg after adding thermal cycles of 200 times. Dye penetration was to located to the enamel of the margin.
4) Scanning electron microscopy evaluation of the solubility on margins of crowns showed that the adhesive resin cement was tolerable in 1/100N lactic acid solution for 12 hours, although most of cements was decayed remarkably.

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This article discussed the dimensional accuracy of Olympus Castable Ceramics (OCC) crowns at the stage of as-cast and crystallization. The master die technique and three coordinate measuring method were used for their measurement. Moreover, the surface roughness of inner crowns were measured and following results were obtained.
1. OCC crowns, heat-treated at 850°C were rather expanded than at 900°C or 950°C in the master die technique. But the differences between at 900°C and 950°C were not significant.
2. In the master die technique, each crown fabricated with special investment liquid, which was diluted with 25%, 50% and 75% distilled water showed expansional ratios of 0.35%, -0.23%and -0.86%, respectively.
3. In the master die technique, buffering factors, ringless, one fold of liner and two folds of liner did not affect the expansional ratio.
4. In three-coordinate measuring, each diameter of as-cast crowns expanded equally in the range of 1.0-7.0mm from occlusal plane. But, 9.0mm near the cervical portion expanded less than the others.
5. In three-coordinate measuring, about 0.70-0.81% shrinkage were founded at the inner diameter of crystallized crowns.
6. In measuring for surface roughness of inner crowns, crystallized crowns were roughened more than as-cast ones in both of Ra and Rmax.

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Experimentally thermal expansion inhibited investment was produced to discuss a problem, the compensation of metal casting shrinkage is to be dependent upon setting expansion. Using the various concentration of colloidal silica solution as mixing liquid, idealized full cast crowns were made, the each size were measured and the following results were obtained.
On this investment:
1. As the more concentration of silica, the more expansion appeared.
2. The shrinkage in cooling is slight.
3. The expansion in ringless method is greater than that of ring method.
On the deformation of crowns:
1. In the external width, both ring and ringless method in 10% and 20% showed shrinkage, the more concentration, expansive tendency appeared. The inhibition of expansion appeared in 40% by ring method. The expansion of cervical showed larger than occlusal.
2. Internal width in 10% appeared shrinkage by both methods, they showed more expansion, increasing of concentration. The internal tendency appeared that occlusal was greater than cervical. The expansion of internal showed greater than external.
3. Despite of methods the more expansion appeared, increasing concentration. The more expansion appeared in the internal height than in external.
The mention above following conclusion were obtained.
It was cleared that the various deformation of crowns appeared due to the setting expansion of investment alone. Accordingly it was considered that the deformation occur in the stage of setting expansion before thermal stage in the present dental casting procedure. It can be said that the setting expansion is the great factor of the deformation in cast crowns.

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It is practically difficult to seat the full cast crown satisfactorily on the prepared tooth during cementation. Two clinical technics have been adopted so far to aid better seating of the crown restoration : (1) internal surface relief and (2) perforation of the crown to provide a vent for the cement to escape. The present article describes a newly designed crown restoration to minimize the elevation of the crown at the margin. It consists of an internal crown covering the axial surface up to the finishing line and an ordinary, external crown over the internal one. On cementation of the internal crown, the cement can easily escape toward the open occlusal plane, and the resultant average cement thickness between the internal crown and the tooth becomes as thin as 4.8μm at the margin. It indicates that the adequate application of such an internal crown would allow the cast crown restoration to seat more completely and reduce the influence on the marginal gingiva.

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Periodontal diseases and arthrosis of temporomandibular joint attributed to inadequate crown or bridge have recently been increasing. To prevent these diseases the functional performance of the prosthesis should be checked by temporarily cementing for some period prior to final fixation. However, very few descriptions were found on the elevation of the crown or even on the film thickness with temporary luting cements for that purpose. In this study, therefore, the elevation of the crown by cementation with temporary and permanent luting cements was examined using experimental crown and abutment tooth models. The space between the crown and abutment was approximately 30μm both at the axial and occlusal plane when the crown was seated on the abutment without cement. The decreasing rate of the elevation of the crown with time under loading was significantly different among the cements, suggesting that the outflow of the cement slurry from the crown margin might be markedly affected by its thixotropical behavior and particle size as well as its consistency. As for the effect of the particle size, it seemed rational to refer the maximum size of the residual particles after setting rather than that of the original powder particles. The temporary luting cements used were devided into two groups showing elevations as small as 4 to 14μm and more than 120μm, respectively. On the other hand, the elevation with the permanent cements ranged from 6 to 47μm. The applied load and load initiation time for cementation affected the elevation. No significant changes were found in the elevation if the load application was started within one minute after the end of mixing. It was also found that the load of 5 kg was sufficient for minimizing the elevation by cementation. The results indicate that in order to check the functional performance of the prosthesis prior to final fixation it is essential to properly select the temporary cement showing compatible elevation with the permanent cement to be used.

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The purpose of this study was to investigate the accuracy of working casts fabricated by a transfer system. A master model was fabricated from a single standing ITI implant with a solid abutment. Working casts were fabricated from two methods.(One was a stone-model using the conventional method, and the other was a transfer-model using the transfer system with an impression cap and a shoulder analog.) A profile projector was used to measure the dimensional changes of dies. The conclusions were as follows:
1. Regarding the dimensional change of dies on transfer-models, the width of the joint part and the height of the shoulder were as accurate as those on stone-models; however, the width of the abutment was slightly small, and the height of the abutment was slightly large.
2. The distortion of reference points on stone-models had a tendency toward upper and outside. On transfer models, reference points of the upper part of the abutment had a similar tendency, however; those of the joint part and the shoulder edge distorted toward lower.
3. The distortion of the center point on stone-models had a tendency toward upper; however, that on transfer-models scarcely distorted.
4. On both models, there was little inclination change in the long axis.

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ビニルシリコーンゴム印象材を使用した各個トレー法によって,金属製支台歯原型の印象採得を行い,得られた歯型から鋳造冠を作製した.そして,歯型に対する適合状態をマージン部の浮き上がり量から,原型に対する適合状態をマージン部の浮き上がり量および内面間隙量から検討した.その結果,内面の適合調整を行った鋳造冠は,アズキャストのものに比較して,歯型に対する浮き上がり量が小さかったが,原型に対する浮き上がり量および内面間隙量はほぼ同等であった.また,原型に対する内面間隙量では,鋳造冠上面に適合検査材の溢出孔を設定することによって,軸方向においてもセメント合着した報告値と同程度の間隙量を求めることができた.そして,マージン部の浮き上がり量および内面の間隙量の両者を求めることで,原型に対する鋳造冠の適合状態をより詳細に検討することができた.

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歯は人体組織中で最も硬く, 物理化学的に安定した物質であり, 個人識別上多くの要素を持っている。そこで, 歯および歯の類似物, そして一般歯科領域で使用されている物質を同定しやすい方法で調べておくことは, 実際に歯であるか否かの判定に際し, また歯の類似物のうち果して何んであるかを決定づけるのに大いに役立つものと考えられ, 法歯学実際上非常に重要な項目である。
そこで, 歯および歯の類似物, その他広い範囲の歯科関連物質を集め, 用途別に分類し, 赤外線吸収スペクトル法を用いて歯と比較検討を行なった結果, 人の歯と動物の歯との違は見られないが, 各エナメル質と象牙質との区別は比較的容易にできる。また外観上は歯の硬組織と類似する種々の歯科用材料でも, 同様に容易に判別することができるので, 法歯学上極めて重要な基礎資料を提供するものと思われた。

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In this study, the surface roughness and the axial taper of dies were varied and ther influences on the elevation of the complete cast crowns after seating were studied. The result were as follows:
1. Impression materials should have a reproducibility of at least 30-50 μm Rz of surface roughness.
2. At each degree of the axial taper, there was a special range of surface roughness, where the inner surface roughness of the crowns and their elevation increased remarkably.
3. The elevation of the crowns grew proportionally larger, as the surface roughness became larger.
4. Within the range of 4deg;-12deg; of axial taper, GROUP 1 showed the largest elevation at any stage of surface roughness.
5. When the axial taper reached the level of 8deg;-12deg;, elevation of the crowns decreased.
6. When the elevation, the retentive force and other practical factors were taken into consideration, the recommendable surface roughness would be 8μm Rz at 4deg;of axial taper, 30μm Rz at 8deg;, 12deg; and 50μm Rz at 16deg;.

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試作した硬化膨張型埋没材, 加熱膨張型埋没材, 市販リン酸塩系埋没材など計6種の埋没材を用いて, インレーワックスブロックより旋盤にて作製した円板および中空円板をワックス原型として, 鋳型温度700℃にてKメタルを遠心鋳造した.鋳造体とワックス原型との内径, 外径, 厚さの変化を読み取り顕微鏡にて計測し, その寸法変化率を鋳造精度とした.外径の寸法変化率は, 円板も中空円板も同じ結果を示した.硬化膨張型埋没材では外径より内径の寸法変化率が小さくなり, 加熱膨張型埋没材では逆の傾向になった.鋳造精度は, 硬化膨張率との間には正の相関を, 加熱膨張率との間には負の相関を示した.

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In order to clarify changes in the inner surface of posterior resin crowns in response to polymerization, changes in the contour of the inner surfaces of these crowns (1.0, 1.5 and 2.0 mm in thickness) under conditions of light polymerization or light and heat polymerization (heat polymerization) were determined by a three-dimensional measurement system, and changes with light polymerization were compared with those of heat polymerization. The results are summarized as follows:
1. Under conditions of both light and heat polymerization, the inner surface shrank at all measurement sites and the amount of shrinkage with heat polymerization was greater than that with light polymerization.
2. Under conditions of both light and heat polymerization, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. This tendency was marked under the light polymerization condition.
3. Dimensional changes were observed, i.e., -16μm with light polymerization and -28μm with heat polymerizaiton, at a site 6 mm from the occlusal surface, -11μm with light polymerization and -30μm with heat polymerizaiton at a site 8 mm from the occlusal surface, and -8μm with light polymerization and -27μm with heat polymerization at the dental neck. There were significant differences in dimensional changes between light and heat polymerization at the site near the dental neck on the axial wall.
4. When the thickness of the resin crown was 1.0, 1.5 or 2.0mm, the inner surface shrank at all of measurement sites. With the increase in thickness, the amount of constriction was increased.
5. When the thickness of the resin crown was 1.0 or 1.5mm, the amount of shrinkage was decreased in the region ranging from the occlusal surface to the dental neck, showing a claviform pattern. When the thickness was 2.0mm, the amount of shrinkage was almost fixed. The ten-dency to form a claviform pattern with the 1.0mm-thick crown was greater than that with the 1.5 mm-thick crown.
6. There were significant differences in all dimensional changes except height, at all measurement sites on the axial wall, between the 1.0mm-and 1.5 mm-thick crowns, and at all of measurement sites, except the occlusal surface, between the 1.0mm-and 2.0mm-thick crowns. There was a significant difference in the dimensional change of height between the 1.5mm-and 2.0mm-thick crowns.

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