[in Japanese]

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Intracellular and extracellular invertase-like enzymes were purified from Prevotella oralis (formerly Bacteroides oralis) Ig4a by combination of several ion-exchange chromatography and gel filtration steps. The intracellular enzyme was purified as an electrophoretically homogeneous protein, and the extracellular enzyme was partially purified. The molecular weights of intra- and extracellular enzymes were estimated to be 79,000 and 53,000, respectively, by SDS-polyacrylamide gel electrophoresis. Both enzymes specifically cleaved sucrose and raffinose, but not melezitose and other polysaccharides tested, implying that the enzymes are invertases (EC 3.2.1.26; β-D-fructofranoside fructohydrolase). The intra- and the extracellular invertases had optimal pHs of approximately 6.5 and 5.5, optimal temperature of 35°C and 55°C, and Km values of 14.2 mM and 66.7 mM, respectively. These enzymes were inhibited strongly by Hg²⁺, and weakly inhibited by Zn²⁺ and Fe³⁺. The antiserum against the purified intracellular invertase revealed by Ouchterlony analysis that the two invertases were antigenically related

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Plate specimens were prepared using three hybrid-type composite resins for a posterior used and one MFR-type for an anterior use. Specimens were immersed into alcohol (99. 5% ethyl alcohol), acid solution (1 mol lactic acid), alkaline solution (1 mol sodium hydroxide) and deionized water up to 2 months. Water sorption, solubility, surface roughness and SEM observation were examined to evaluate the environmental durability of composite resins.
Water sorption and solubility were increased and cracks were observed along the interface between organic fillers and a matrix resin on the MFR-type composite resin under an alcoholic environment. Cracks were also observed along the interface and also inside the filler on the hybrid-type composite resins under an alcoholic environment.
Surface deterioration such as the small cracks and failure of inorganic fillers was found on the hydrid-type composite resins but less deterioration was found on the MFR-type composite resin under acid environment.
Surface severe deterioration such as the dissolution and failure of inorganic fillers was observed on all composite resins under alkaline environment. Surface roughness of specimens under an alkaline environment increased with increasing immersion periods. It was difficult to evaluate the difference among specimens under an alkaline condition because all the specimens suffered from severe deterioration rather similarly.
Therefore, environments with alcohol and acid were more appropriate to find the difference in deterioration among the specimens, and to be used as media for evaluating durability in accelerated conditions. Furthermore, deterioration of composite resins was affected by many factors such as the interface of fillers and matrix resin, composition of materials, and environments complicatedly

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Properties of three kinds of calcia powder (CFQ-S CSQ-S and CFQ-E) were investigated to be applied to investments and crucibles for titanium castings. There were great differences on particle distribution and activity among calcia products according to process to be prepared and their purity. Especially, sintered calcia (CFQ-S and CSQ-S) showed higher activity than fused calcia (CFQ-E) and had shorter setting time. Green strenghs of sintered calcia were affected by both environmental temperature and storage time, which were highest at 10°C for 24 h in this study. On the other hand, fused calcia had longer setting time and lower green strength, when stored in lower temperature.
The thermal expansion of each calcia mold which was mixed with titanium powder as an expanding agent was large enough to compensate casting shrinkage of titanium.
There was obviously a relationship between the purity of calcia powder and the hardness of titanium castings obtained from the calcia crucible and mold using an induction melting casting apparatus. Titanium castings obtained from CFQ-S, which had the highest purity, showed the lowest hardness (Hv).
These results suggest that sintered calcia (CFQ-S) with high purity seems promising to be applied to investments and as mold crucibles for titanium castings because of an easy manipulation, excellent properties and less reactivity with titanium

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In old dental calculus attached to human teeth, the hexahedrally based crystals of whitlockite were frequently formed in the various intra-spaces of calculus deposits and the interface of calculus and the teeth. Thus, we suggest that such crystal depositions cause the maturation of dental calculus to accelerate

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We have reported that some filamentous and rod-shaped microorganisms in human dental calculus were replaced by the hexahedrally based crystals of whitlockite. Morphologically, such rocky pile-shaped deposits in subgingival, marginal (ledge-type), and deep subgingival (spiny) calculi were more or less distinguishable. This may be caused by the differences of the microbial flora, and the supplied Mg content and pH range derived from either saliva or gingival fluid

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Recently, titanium plates have been introduced in the reconstruction of jaws in oral surgery. However, properties of titanium plates have been unclarified yet. In this study, commercially available and experimentally fabricated titanium plates and screws were investigated. Commercial stainless steel plates and screws were also used as a control. Element analysis with XMA, SEM observation, metallurgical observation, hardness measurements, and tensile tests were performed. In addition, the fractured surface of the clinically fractured plates were observed by SEM. Some plates and screws were made from Ti-V-Al alloys and others were pure Ti. And the combination of Ti alloy and pure Ti for the plate and screw was different in each system. Surface topography showed both relative smooth and rough surface on the plates which depended on the fabricating process of the products. Metallurgicall structure was also different among products. The hardness of plates and screws with Ti alloy was much higher than that with pure Ti. The Ti plate showed higher proof stress and lower tensile strength than the stainless plate. Brittle fracture was observed on the fractured surface of the clinically fractured plates. These findings suggest the unique properties of titanium plates should be considered in clinical application

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The purpose of this study was to determine the statistical information concerning the crowns and the fixed partial dentures (total number, types and rate of crowns, number of vital or non-vital abutment teeth, etc.) made by the staff of the First Department of Prosthodontics, School of Dentistry, Showa University from April 1991 to March 1992.
The following results were obtained :
(1) The total number of crowns and fixed partial dentures produced were 1,116 ; among them 903 pieces (81%) were crowns, and the other 213 pieces (19%) were fixed partial dentures.
(2) Most of the crowns were the full cast crowns (553 pieces, 61.2%), secondly were the porcelain fused to metal crowns (253 pieces, 28.0%). However no resin faced cast crown was observed.
(3) Among the crowns for the anterior teeth, the porcelain fused to metal crowns were about three times as many as the jacket crowns. For the premolar teeth, the full cast crowns were about two and a half times as many as the porcelain fused to metal crowns. For the molar teeth, almost crowns were the full cast crowns.
(4) The placement of the fixed partial denture, about 60% restorations were located in the posterior region. Anterior and anterior-posterior region were about 20% to each.
(5) The relationship between the missing teeth and the abutment teeth of the fixed partial denture, the three-unit fixed partial dentures (one missing tooth with two abutment teeth) were most frequently treated
(6) The payment rate of the crowns by the insurance dental service was 68.8% and that of the fixed partial dentures was 68.1%.
(7) Concerning the abutment teeth of the crowns, 88.8% were non-vital teeth. Those rate of the fixed partial dentures were 67.7%.

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The critical surface tension (γc) of CP Titanium (Ti), Co-Cr alloy and Ag-Pd alloy was determined from the Zisman's plots prepared with the data of contact angle which were measured using the solutions with different surface tensions. The Ti plates were heat treated in air to form surface oxides, and the weight increase, surface texture and contact angle of distilled water were examined. In addition, tensile bond strengths of four dental luting cements to the Ti rods with and wtihout heat treatments were measured to evaluate the effect of oxidation on bonding properties.
The critical surface tension (γe) of Ti was higher than those of Co-Cr and Ag-Pd alloys and Ti showed better wettability. Furthermore, the contact angle of Ti plates decreased with the temperature of oxidation increased from 200°C to 600°C. However, oxidation at 800°C increased the formation of oxide films and obviously changed the surface texture of the plates.
Bond strength of resin cement to Ti rods was the highest among tested cements. And bond strength of cyanoacrylate cement was second highest and significantly higher than those of glass-ionomer cement and polycarboxylate cement. Bond strengths of all cements to Ti rods with oxidation at 600°C for 30 min, which showed best wettability, were higher than those without treatments. However, bond strengths to Ti rods with treatment at 800°C were significantly lower than those at 600°C. The fractured surface from the Ti plates at 800°C showed the separation between the mother metal and the oxide film. Since the oxidation of Ti with heat treatments in air increased wettability in a simple way and also increased the bond strength with dental luting cements, we suggest the oxidation with heat treatments was useful to apply Ti in a restorative dentistry.

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On the purpose to clarify the relationship between fibril arrangement of bone matrix surface of mandibles and outward strength to the bone, we examined the surface matrix of various parts of mandible with a high resolution scanning electron microscope.
The materials were mandibles of 3 year-old male crab-eating monkeys. The specimens were dissected free the fibrous layers of ectoperiosteum and incubated in 1% trypsin solution to digest osteoblasts and amorphous organic matrix. These were followed by conductive-staining, dehydration, critical point drying, ion sputter coating and examination with a field emission type scanning electron microscope.
The surface of mandibles was composed of collagen fibril bundles. At the body of mandible, main collagen fibril bundles were running in parallel along the long axis of body of mandible. These bundles were about 1 pm in diameter. At the uneven surface of body of mandible, bundles mingled each other. Bundles were running around the mental foramen. At the base of mandible, bundles were running densely in parallel along the lower border of mandible.
Bundles were running in parallel along the alveolar border. However, bundles were running perpendicularly at the surface of alveolar bone. It was suggested that the arrangement of collagen fibril bundles of alveolar bone was related to the direction of the masticatory strength.
At the surface of ramus of mandible, bundles were running along the long axis of ramus of mandible. At the angle of mandible, many holes into which tendons entered were recognized between bundles. These bundles were running around the holes. At the surface of coronoid process, bundles were running perpendicularly, and dense or sparse tendons were recognized between collagen fibril bundles.

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We reported three cases of a lymphoepithelial cyst arising in the cervix. Case 1 was a 33-year-old female with a mass in the right submandibular region. Case 2 was a 40-year-old male with a mass in the right lateral cervical region inferior to the auricula. Case 3 was a 48-year-old female with a mass in the left lateral cervical region. The initial examination using ultrasonography and CT scan revealed a cyst in each case and thus the lesions were diagnosed as a lateral cervical cyst. These cysts were extirpated and pathological diagnosis of a lymphoepithelial cyst was obtained. Follow-up examination has shown no evidence of recurrence.

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