M Iwaku

Tokyo Medical and Dental University, Edo, Tōkyō, Japan

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Publications (26)50.76 Total impact

  • Journal of Prosthetic Dentistry 01/1985; 52(6):811-4. · 1.72 Impact Factor
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    ABSTRACT: In order to find a substitute for human teeth in the adhesion test, the adhesive strength to bovine teeth was compared with that to human teeth using five dental cements and two composite resins. The adhesion to enamel and the superficial layer of dentin showed no statistically significant difference between human and bovine teeth, although the mean values were always slightly lower with bovine teeth. Adhesion to bovine dentin decreased considerably with the depth of dentin.
    Journal of Dental Research 11/1983; 62(10):1076-81. · 3.83 Impact Factor
  • British dental journal 08/1983; 155(1):19-22. · 0.81 Impact Factor
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    ABSTRACT: When observed by SEM, after being treated with the HCl-collagenase method, the odontoblast processes extended throughout the whole thickness of dentin in intact teeth and the whole thickness of normal and the inner carious dentin in carious teeth. Small holes and depressions were found on the processes in the transparent layer.
    Journal of Dental Research 08/1983; 62(7):798-802. · 3.83 Impact Factor
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    ABSTRACT: The pulpal response to a new adhesive restorative resin was histopathologically investigated using dogs, and was compared with a representative conventional resin. When filled without etching and cavity wall lining, bacterial penetration and pulpal response were less with the new resin. Lining of dentin walls and total etching of cavity walls, including dentin, caused less pulpal response under the new resin. Cavities which were totally etched and filled with the new resin showed only a slight pulpal response and no bacterial penetration.
    Journal of Dental Research 09/1982; 61(8):1014-9. · 3.83 Impact Factor
  • Kōkūbyō Gakkai zasshi. The Journal of the Stomatological Society, Japan 07/1982; 49(2):325-32.
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    ABSTRACT: We have developed a vibration etching technique in which occlusal pits and fissures are simultaneously cleansed and acid-etched using a fissure needle mounted on an electromagnetic vibrator. When tested on extracted teeth, the needle completely cleansed the fissures by removing the contents and the prismless enamel layer, and widened them to from 100 to 150 micrometers to the depth reached by the needle. The sealant penetrated readily and adhered to the reduced and etched fissure walls interlocking with resin tags.
    Journal of Dental Research 07/1982; 61(6):780-5. · 3.83 Impact Factor
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    ABSTRACT: We have developed a vibration etching technique in which occlusal pits and fissures are simultaneously cleansed and acid-etched using a fissure needle mounted on an electromagnetic vibrator. When tested on extracted teeth, the needle completely cleansed the fissures by removing the contents and the prismless enamel layer, and widened them to from 100 to 150 μm to the depth reached by the needle. The sealant penetrated readily and adhered to the reduced and etched fissure walls interlocking with resin tags.
    Journal of Dental Research 01/1982; 61(6):780-785. · 3.83 Impact Factor
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    ABSTRACT: The change of the dentinal tubules by acid-etching and the morphology and the adhering state of new adhesive composite resin tags penetrating the tubules were observed by SEM, comparing with the representative conventional composite resin. When the fractured surface of the unetched floor dentin were observed, all tubule entrances were closed by blocking with cutting debris up to 10 to 20 micrometers depth. Etching opened them by dissolving the debris and further widened the tubule entrances up to 10 to 20 micrometers depth by dissolving the peritubular dentin near the apertures. Resin tags penetrated 10 to 20 micrometers in vital teeth, 60 to 100 micrometers in freshly extracted teeth and several hundred micrometers in old extracted teeth. The tags of the new resin penetrating the tubules copied exactly the shape of the tubule walls, producing hollow depressions at the ends, indicating that the renin polymerized, adhering tightly to the walls, while those of the conventional resin produced highly tapered side walls with pointed ends, indicating that the resin shrank separating from the tubule walls on polymerization. The new resin did not produce any gap at the resin-dentin interface unlike the conventional resin.
    The Bulletin of Tokyo Medical and Dental University 07/1981; 28(2):45-51.
  • K Itoh, M Iwaku, T Fusayama
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    ABSTRACT: 1. Microleakage was prevented when the margins of composite resin restorations were covered with a glaze. The microleakage occurred after the glaze was abraded and removed in vivo and in vitro. 2. The glaze margins gradually separated from the enamel as well as resin surfaces and fractured, creating steps which were apt to cause exogenous staining. 3. Although the glaze coated the restoration, thus producing a smooth surface, the roughness of the composite resin was exposed when the glaze was lost in the oral environment.
    Journal of Prosthetic Dentistry 07/1981; 45(6):606-13. · 1.72 Impact Factor
  • M Iwaku, T Takatsu, T Fusayama
    L' Information dentaire 07/1981; 63(24):2293-8.
  • M Iwaku, T Takatsu, T Fusayama
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    ABSTRACT: Three types of luting cements were compared for acidity, disintegration, and film thickness. The pH during setting of the two types of polycarboxylate cements exceeded 6 after 5 hours; that of the water-settable polycarboxylate cement was the highest, almost reaching neutral. The zinc phosphate cement reached pH 3.4 after 5 hours and 5.5 after 24 hours. All cements tested showed remarkably greater disintegration in the lactic acid solution than in the distilled water. The disintegration of the water-settable zinc polycarboxylate cement in distilled watter was about half that of the other cements. The disintegration in the lactic acid solution was approximately the same for all cements tested. The film thickness was smallest with the water-settable zinc polycarboxylate cement.
    Journal of Prosthetic Dentistry 05/1980; 43(4):423-5. · 1.72 Impact Factor
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    ABSTRACT: Non-pressure adhesion of a new adhesive restorative resin was investigated employing a new tensile test. The material was adhesive to both enamel and dentin as well as to carious dentin and showed strong adhesion to all substrates tested. Etching further increased the adhesion even to dentin.
    Journal of Dental Research 05/1979; 58(4):1364-70. · 3.83 Impact Factor
  • E Koyano, M Iwaku, T Fusayama
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    ABSTRACT: 1. Dynamic pressure produced thinner cement films than static pressure. The cement film was thinner with vibratory pressure than with the mallet. The thickness was slightly less with vertical vibration than with horizontal vibration. Horizontal vibration seemed preferable because it could be used with increased pressure without causing trauma or pain. 2. The combination of static pressure followed by dynamic pressure produced thinner cement films than any individual pressuring technique. 3. The optimal technique for clinical use is to seat the casting by finger pressure and then apply horizontal vibration under hand pressure.
    Journal of Prosthetic Dentistry 12/1978; 40(5):544-8. · 1.72 Impact Factor
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    ABSTRACT: In order to confirm the ability of physiological recalcification of the human carious dentin, the first layer of carious dentin was removed from the symmetric cavities of bilateral pairs of human teeth, disclosing it by 0.5% basic fuchsin-propylene glycol solution staining. One of the pair teeth was immediately extracted and the other was left in the mouth after filling the cavity with polycarboxylate cement. The Ca content and hardness of the remaining second layer immediately and three months after the operation were compared by an electron probe microanalyzer and microhardness tester. They increased markedly after three months returning to the normal level from inside, proving physiological recalcification. A similar experiment was performed by using bilateral pairs of dog teeth with cavities having artificially decalcified dentin floor. After removing the fuchsin-stainable first layer, one of the pair was immediately extracted and the other was left in the mouth for three months after exposing or filling the cavity with various cements. As the Ca content was compared, a marked recalcification of the second layer of softened dentin was observed after three months returning to the normal level from the inside. The effect of different cavity treatment was slight.
    The Bulletin of Tokyo Medical and Dental University 10/1978; 25(3):169-79.
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    ABSTRACT: The dimensional factors of the cervical undercut of the human teeth were measured. The facial and lingual undercuts showed considerable deviations in depth, width, and inclination to the crown axis and the food stream. The proximal undercuts showed a uniform depth of 1 +/- 0.3 mm with some deviations in width and inclination.
    Journal of Dental Research 04/1978; 57(3):484-94. · 3.83 Impact Factor
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    ABSTRACT: The application of GK-101 to carious dentin softens the first or outer layer which contains denatured collagen. The second or inner layer of carious dentin, containing normal collagen fibers, is unaffected. The pulps of dog teeth were not affected by applying the solution to freshly prepared sound dentin.
    Journal of Prosthetic Dentistry 09/1977; 38(2):169-73. · 1.72 Impact Factor
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    ABSTRACT: Three non-gamma2 and one conventional amalgams were compared for their structure and hardness. The Ag-Cu dispersants hardened the amalgam by generating hard Cu-Sn halos and diminishing the gamma2 phase. The Ag-Sn-Cu-In single composition alloy produced the hardest amalgam by its high hardness and the Cu-Sn reaction phase scattered as minute granules.
    The Bulletin of Tokyo Medical and Dental University 04/1977; 24(1):73-80.
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    T Takatsu, M Iwaku, T Fusayama
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    ABSTRACT: The metallurgical structure of a non-gamma-2 amalgam was investigated by using metallurgical microscopy, surface, point, and line analyses by an electron probe microanalyzer, and a microhardness test. Referring to these findings, their effects on clinical results were then discussed. Findings were as follows: The residual dispersant particle was less hard than the gamma 1 matrix, but the ring around it was much harder than the gamma 1 matrix or the residual gamma particle. The improved mechanical properties seem to be the result of the presence of this ring. The gamma 2 phase was absent in this amalgam. The absence of gamma 2 phase seems to improve chemical resistance, to prevent the deformation by mercuroscopic expansion of amalgam margins, and thus to decrease their fracture potential. The minute gamma 1 crystals found adjacent to the ring around the residual dispersant particle seem to indicate that they were late in crystallization, resulting in low early strength.
    Journal of Dental Research 02/1977; 56(1):40-5. · 3.83 Impact Factor
  • Journal of Prosthetic Dentistry 11/1976; 36(4):409-15. · 1.72 Impact Factor