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Volume 21 (1954)
- Issue 4 Pages 153-
- Issue 3 Pages 87-
- Issue 2 Pages 51-
- Issue 1 Pages 1-
Volume 21, Issue 1
Displaying 1-8 of 8 articles from this issue
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Corrosion Resistance of Titanium and ZirconiumIsi Miura, Minoru Sakurai1954 Volume 21 Issue 1 Pages 1-5
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSAccording to the recent studies, titanium and zirconium, the refining method of which was recently found by W. J. Kroll, seem to be hopeful for dental use on account of their excellent mechanical properties and resistance to corrosion. So the authors intended to study the application of these metals for dental use.
Corrosion resistance of titanium, zirconium, Ni-Cr alloy and 18-8 steel are described in this report. Ni-Cr alloy and 18-8 steel are used in this country as the substitutive metal for dental gold alloys. Titanium and zirconium showed a strong resistance to corrosion by 1% NaCl, 0.05% HCl, 1% lactic acid and 0.1% Na2S, however Ni-Cr alloy and 18-8 steel were corroded in some cases (Table 1) . Titanium and zirconium did not lose their metallic brightness against 1% acids and zirconium was most resistant to corrosion by 50% acids (Table 2) . From these facts it could be concluded that titanium and zirconium were better dental materials with respect to corrosion resistance.View full abstractDownload PDF (4321K) -
Heating of TitaniumIsi Miura, Koji Tutiya1954 Volume 21 Issue 1 Pages 6-11
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSThe purpose of this investigation was to make clear the effect of gases on thin commercially pure titanium sheet when heated at various temperatures up to 1000°C.
Studies were made on increase in weight, hardness and structure on those specimens heated in air, in a oxygen of 150 mmHg and in vacuum for one hour. In case of heating below 800°C the general trends on the hardness and microstructure were same in different atmospheres, while hardening gradually became marked above 800°C. Specimens heated in air and in oxygen at 1000°C showed a significant increase in hardness and weight, but comparatively small when heated in vacuum. Large Widmanstätten plates appeared in microstructure of those specimens heated in air and in oxygen.View full abstractDownload PDF (3067K) -
I. Surface Hardening Method by Chemical Treatment of Plaster MouldTeiroku Sueno, Kazuo Kato, Takaaki Hata1954 Volume 21 Issue 1 Pages 12-17
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSA new method to harden the surface of plaster mould by dipping in solution of ZnSO4, FeSO4, MgSO4, MnSO4, Al2 (SO4) 3 CaSO4 etc is described in this report.View full abstractDownload PDF (706K) -
Copolymers of Methylmetacrylate with Allylsilicate as Crossrinking AgentsEiiti Masuhara, Kuniharu Kojima, Niro Tarumi1954 Volume 21 Issue 1 Pages 18-20
Published: 1954
Released on J-STAGE: December 08, 2010
JOURNAL FREE ACCESSPowerful plastics was made by the copolymerization of methyl metacrylate with allyl silicate. Allyl silicate (CH3) Si (O-CH2-CH=CH2) 3, (CH3) 2Si (O-CH2-CH=CH2) 2, (CH3) 3SiO-CH2-CH=CH2) as crossrinking agent was prepared by the reaction of methyl chlorosilane with allyl alcohol. Allyl silicate obtained by this reaction is a new kind of compound. Only allyl silicate did not polymerization using benzoyl peroxide catalyst, but the copolymerization of allyl silicate with methyl metacrylate results in polymers containing only small amount of allyl silicate. With methyl metacrylate only about few mole per cent of allyl silicate was found in the copolymer. Wheres allylsilicate is completely unreactive toward this compound give extensive reaction. The allyl silicate methyl metacrylate copolymers are hard, brittle resin, insoluble in either, aceton etc.View full abstractDownload PDF (342K) -
Eiiti Masuhara, Niro Tarumi, Tadasi Hirasawa1954 Volume 21 Issue 1 Pages 21-26
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSAverage Polymerisation degree of polymethylmethacrylate was measured by several methods, (viscosity method osmotic measurements, quantitative analyst of the end group of moleculars and Wijs' method etc.) but those values were different by each method (Table 1) .
Viscosity method in chloroform solution has been discussed by Japanes two makers (Mitubisi Rayon Co. and Fuji Kasei Co.) and our research institute.
The authors measured average polymerisation degree of denture base and direct resins by means of viscosity method under the following condition: Ostwald's viscosimeter was used at 20°C, And chloroform solution was placid more than for 48 hrs, at room temperature, since polymer had begun to resolve by the quantitative chloroform. Concentration of solution was 1g/l to 10g/l and then average polymerisation degree was calculated by Schulz's equation.
Intrinsic viscosity was obtained by the following four methods:
i) graphic method (plotting relation of ηsp/c-c),
ii) graphic method (plotting relation of lnηrel/c-c),
iii) Schulz's equation, and
iv) Sakurada's equation.
Intrinsic viscosity and average polymerisation degree are shown in Tables 2 and 4.
As shown in Table 4, it could be concluded as follows:
When the authors made the determination of average polymerisation degree of polymethylmethacrylate for dental use by viscosity method in chloroform solution under the same experimental condition by the use of the same equation calculating average polymerisation degree, difference of the average polymerisation degree is about 10 per cent by difference of method getting intrinsic viscosity.View full abstractDownload PDF (603K) -
Eiiti Masuhara, Kuniharu KOJIMA, Kitizo TANAKA, Niro Tarumi, Tadasi Hi ...1954 Volume 21 Issue 1 Pages 27-32
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSAs polymethylmethacrylate as dental materials does not have sufficient toughness and mar resistance make artificial denture and denture base by the use of nylon. Amilan chipps (Toyo Rayon Co.) were used and the authors molded by vertical hand pressure molding machine (Fig. 3) as follows: put a proper quantity of amilan chipps in the heating cylinder, as soon as amilan chipps were melted, quickly set the mold of hard plaster on the top of cylinder and pushed out plunger by hand pressure and molded the melting amilan in the mold of plaster.
Used Amilan chipps were dried by the vacuum dryer for giving wrong mechanical properties of the molded products when content with a moisture. This method is characterized of using the mold of plaster instead of the mold of metal.
Artificial denture and denture of nylon have the following characteristics:
A) Many products are made within a short period.
B) Products have toughness and carelessness of breaking semi-parmanently.
C) Complicated molded product can be made comparatively.
D) Non-crasp-denture can be made.
However the following disadvantages could be noticed:
A) Gradual discoloration appears dirtily in the mouth
B) Not so beautiful as polymethylmethacrylate resin
C) Shrinkage is so remarkable due to insuffiecency of molding pressure
D) Flexibility is marked
As suffiecent pressure could not be given in this machine because of using hand-pressure did not have perfect good properties of nylon.
Thus the authors are trying to remove these disadvantages and to improve this machine.
Further studies on its clinical use will be published in the near future.View full abstractDownload PDF (3507K) -
Atuyosi Muramatu, Nobuhiro Siokawa, Itiro Nakahara1954 Volume 21 Issue 1 Pages 33-41
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSThe author's experiences in connection with the investigation of maximum stress and stress distribution of the full denture base in the dental domain are described in this paper.
The upper and lower full dentures were bitten each other and compressed between two plates up to a maximum load of 40kg. The brittle coating made in our laboratory was coated on the same six full denture bases and the strain gauges were cemented to five positions over an upper full denture base along the direction normal to the crack. The crack sensitivity of the coating and strain sensitivity of the gauges were calibrated by means of the cantilever bending tests of the same resin strip as the full denture base.
The main tensile crack pattern appears lengthwise in the middle region of upper full denture base, and when they are subjected to the load of 10 kg, maximum tensile stress caused in the back edge region is evaluated above 0.7 kg/mm2.View full abstractDownload PDF (8729K) -
Syoiti Terada1954 Volume 21 Issue 1 Pages 42-46
Published: 1954
Released on J-STAGE: October 08, 2010
JOURNAL FREE ACCESSWater soluble salt of hydro-fluoric acid are applied to teeth for the purpose of preventing dental caries and the following results were obtained:
(1) . Resistance to weak acids, such as organic acids, is lowered by means of application of water soluble salt of hydro-fluoric acids.
(2) . Teeth become more brittle.
(3) . When these water soluble salt of hydro-fluoric acid are absolved into the body, the soluble calcium salt in the body are converted into insoluble salts and brings about a condition where the body is lacking in calcium with resulting disorders. Furthermore, the presence of excessive amounts of fluoride is directly deleterious to the human body.
(4) . As long as water soluble compounds of fluorine are in the mouth, developement of micro-organisms is hindered and therefore prevents the formation of acids. Therefore it is clear that only in Case 4 is the prevention of caries carried out by preventing oval fermentation. Cases 1, 2 and 3 show that the use of fluorine compounds is disadvantageous.
If only the object is to prevent formation of acids, one can use some other harmless substance beside sodium fluoride.
Furthermore, fluorine is usually considered to be not necessary for mammalia. Therefore, the conclusion is that it is not advisable to use compounds of fluorine in the prevention of dental caries.View full abstractDownload PDF (694K)
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