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Biomedical subjects

M Iwaku

Publications and source records attributed to M Iwaku.

At least 73 records · Page 4Linked to original sources
PubMed1980

Comparison of three luting agents.

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.

Acrylic Resins↗
PubMed1979

Non-pressure adhesion of a new adhesive restorative resin.

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.

Acid Etching, Dental↗
PubMed1978

Pressuring techniques and cement thickness for cast restorations.

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.

Cementation↗
PubMed1978

Measurements of cervical undercuts of human tooth crowns.

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.

Bicuspid↗
PubMed1978

Physiological recalcification of carious dentin.

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.

Animals↗
PubMed1978

Marginal closure of non-gamma2 amalgam.

In order to investigate the effect of burnishing on the marginal closure of non-gamma2 amalgam restorations, a single-composition high-copper alloy (Indiloy), a conventional lathe-cut alloy (Lunargent Alloy), and a conventional spherical alloy (Shofu Spherical) were each mixed with mercury and filled in transparent plastic cavities. Half of the specimens were burnished along the cavity margins immediately after packing and again after carving. The remainder was unburnished. A dye was sprayed on their occlusal surfaces after 24 hr and leakage indicated by the dye penetration was observed through the plastic walls, and following facts were found: 1. Burnishing markedly decreased the leakage of all type alloy amalgams. 2. When burnished, the marginal leakage with the high-copper alloy was remarkably less than with the conventional spherical alloy but slightly more than that with the lathe-cut alloy. 3. The difference in the marginal leakage and in the effect of burnishing among the three amalgams was apparently related to their setting dimensional change curves.

Chemical Phenomena↗
PubMed1977

Effect of a carious dentin softener on the dentin and pulp.

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.

Animals↗
PubMed1977

Structure and effects of non-gamma-2 amalgam.

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.

Chemical Phenomena↗
PubMed1977

Structure and hardness of four types of amalgam.

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.

Chemical Phenomena↗