Various properties of the adhesive opaque resin containing titanium dioxide were investigated. The mechanical characteristics of this type resin are the same as the characteristics of PANAVIA EX, but when as thick as 50 μm can hide the color of various metals. The tensile adhesive strength one month after using this type resin, in adhesion between enamel and Co-Cr type alloy (Metacast) was measured as 20 MPa. In the cases of Ni-Cr type alloy (SB Bondloy I) and another type Co-Cr alloy (Durallium JD), the tensile adhesive strengths were also surveyed after thermal cycles for 20, 000 times, the results being 44.9 MPa and 32.4 MPa respectively. Both of these values exceed the value measured in the case of PANAVIA EX. The value found when we adhered Metacast with Metacast and made thermal cycles for 10, 000 times was consistently 40 MPa.

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Debonding of brackets must be done easily not to create pain or injury to the enamel.
In this experiment, an electric current was run directly into the brackets, and Joule's heat gave the adhesive its softening and thermal expansion so that the brackets fell off quickly from the tooth surface under a suitable load. The temperature of the inner layer of the tooth was measured at the same time.
The time required until the brackets fell off decreased with the increase of voltage and load. The raise in temperature decreased with a decrease in the bracket falling time. The sample which fell off in the shortest time in this study required about two seconds, and the raise in temperature at dentino-pulpal junction was scarcely detected.
These results suggest that Joule's heat has some possibility of application in debonding.

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Use of light-activated composite resins have advantages over chemically activated composite resins, such as no need to mix pastes and more working time. However, the light-activated composites have a disadvantage in that they do not cure effectively at the base of the deep restoration, because a minimum intensity of light must reach it for an effective cure.
This study examined the effects of the refractive indices of base resins and fillers in the light-activated composites on the depth of cure. Several kinds of dimethacrylates were used as base resin monomers and colloidal silica was used as a filler. As a result, the monomer which has a similar refractive index to that of silica transmitted light effectively and cured deeply. The polymer had a larger refractive index than that of the monomer and the cured resin containing a filler hardly transmitted light.
It is inferred that the monomer which has a refractive index similar to that of the filler and does not change during polymerization will enhance the depth of cure of light-activated composite resins.

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Five casting methods available for Ni-Cr alloys for crown and bridge were evaluated in terms of the tensile properties of the castings as well as the temperatures of the melt at casting and oxygen and nitrogen uptake. The effects on the tensile properties of precious alloys were also examined for three typical casting methods.
The tensile strength and elongation of the Ni-Cr alloys were greatly affected by the casting method, especially by the heating source and the surrounding atmosphere. These effects varied among the alloys used. For all the alloys, however, the casting by induction in argon gas tended to show higher tensile strength and elongation than that by the other methods: induction in air, oxygen-propane flame, arc in argon gas, and arc in argon-blowing atmosphere in air. The temperature of the melt at casting with induction in argon gas was the lowest and the most stable of the five methods. The oxygen and nitrogen uptake in pure Ni casting was also the lowest when this method was used. The tensile properties of the precious alloys were hardly affected by the different casting methods: induction in argon gas, gas-air flame, and electrical resistance.

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To develop some new investment material for higher temperature casting, the alumina investment which consists of pure alumina powder and alumina sol was tested.
For comparison, other bonding materials such as H₃PO₄ or α-plaster were also tested.
In order to select the particle shape and the size distribution, the compressive strength, thermal expansion, and setting expansion were first measured.
The findings were as follows.
1) Alumina-alumina sol slurry was settable, the best formula was 50% coarse (50 μm), 45% medium (8 μm), and 5% fine (2 μm) powder mixed with 20% concentration alumina sol.
2) In this case, the 48 hr green strength was 4.5 MPa, the heated strength was 6.2 MPa, the thermal expansion at 1000℃ was 0.7%, and the setting expansion was -0.17%.
3) Alumina powder was settable with 10% phosphoric acid, and was possible with Co-Cr alloy casting.
4) Alumina powder mixed with 5% α-plaster was also settable.
5) The casting test of titanium alloy or Co-Cr alloy with alumina sol bonded alumina investment showed better results than phosphate bonded silica investments.
6) To shorten the setting time, the suction investing method was useful, and addition of absolute alcohol or dried atmosphere was also effective.

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Liposomes are now widely studied as model membranes to clarify the mechanism of drugs in the biological systems.
Since little was known about the interaction between membrane lipids and phenol disinfectants such as formocresol (FC), and camphor carbol (CC), this experiment studied the effects of these compounds on phosphatidyl choline, dimyristory and dipalmitoyl phosphatidyl choline, and dimyristoyl and dipalmitoyl phosphatidyl ethanolamine liposomes. This was accomplished with the application of spectrophotometers (absorbance 450 nm) and differential scanning calorimetry (DSC).
From the results on the turbidity of liposomes and on the phase transion properties (transition temperature T, enthalpy ΔH, entropy ΔS and H/HHW (height/half-height width) of DSC), it was found that FC and CC had a biphasic effect on liposomes in the dilution range.
The turning point of FC was 1/10³ dilution and CC 1/80-1/160.
A labilization with a decrease of T, ΔH, ΔS and H/HHW was observed at high concentration.
The interaction of CC with liposomes was higher than that of phenol.
The mechanism of membrane damages caused by phenol disinfectants used in dentistry was considered.

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A testing apparatus was devised to evaluate the grinding performance of tools; the tool engagement was set, and the depth of cuts were measured throughout successive strokes of the work at constant speeds. Using a 13% Cr-Ni alloy, the performance of a CBN-electrodeposited wheel was compared with that of two vitrified-bond alumina wheels on the market.
Because of the run-out effect of the wheels, there were some differences in grinding action between rotational speed of 22, 000 rpm and speeds below 18, 000 rpm. At the high speed the ground surface was very wavy, and the final depth of cut exceeded the engagement. At lower speeds the surface was relatively even, but the engagement tended not to be entirely removed. Also at high speeds of work, the grinding had to be repeated many times for a certain depth of cut, and a lot remained uncut.
In consideration of run-out, the CBN-electrodeposited wheel was tested at only 12, 000 rpm. Nevertheless, it exhibited high performance even at the high speed of work.

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1) The water-powder ratio of Type II was influenced by the specification method and the kind of plaster, and a constant relationship was observed in this method. This relationship was not recognized in Types III and IV.
2) With a cosistent water-powder ratio, the setting times of all plasters tested in this study increased in the sequence of JIS, ISO, ADA, despite the kind of plaster used. When the water-powder ratio complied with standard testing consistency, the setting times of Type II increased in the order of ADA, JIS, ISO, but Types III and IV's increased in the sequence of JIS, ISO, ADA.
3) The working time of Type II was 2.20〜2.30 minutes. For Types III and IV, it was three times as long as Type II.
4) In case of practical testing consistency, the relationship between the working time and the setting times was recognized; the working time was shorter than the setting time by about 20〜31% in Type II, and by 53〜82% in Types III and IV.

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Twenty kinds of phosphate-bonded investments were prepared by mixing commercial glass beads (as a base), and magnesia clinker and NH₄H₂PO₄ (as binders). The amount of binders varied from 20% to 5% with the magnesia clinker to NH₄H₂PO₄ ratios of 10/10 and 6/14. The particle size of glass beads varied from L size (90 μm in diameter) to S size (6 μm in diameter). Three kinds of 20% colloidal silica solution were mixed with the investment powders at the ratio of 0.24.
The findings were as follows:
(1) The setting expansion decreased with a decrease in the amount of binders.
(2) The setting expansion depends not only on the porocity of aggregation of glass beads but also on their surface area.

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4-Methacryloxyethyl trimellitate anhydride (4-META) is a good monomer to promote adhesion of resins to enamel, dentin and dental metals. Application of 4-META to conventional BPO-amine self-curing resin had been difficult because of charge transfer complex formation between 4-META and the amine. The purpose of this study is to make a bonding agent with 4-META, which improves the bond strength between BPO-amine self-curing resins and tooth substrates.
The best compositions among studied bonding agents were two liquid systems, the one contained 2 wt% 4-META and 0.5 wt% BPO in MMA and the other had 2 wt% sodium p-toluensulfinate in MMA and ethanol solution. Tensile bond strength was 18 MPa to etched enamel and 7 MPa to 10-3 treated dentin joined with BPO-amine self-curing acrylic resin, and 17 MPa to etched enamel and 3 MPa to 10-3 treated dentin joined with conventional composite resin. This 4-META bonding agent showed bond strength as good as the Clearfil new bond.

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For the suitable adhesion of the resinous cement to the crown and bridge, it needs some pre-treatment to the surface of alloy as adherend.
In this study, the effectiveness of the oxidation treatment, which is one of the recommended techniques of surface treatment, was investigated by measuring the shear adhesive strengths of four brands of dental cements to four types of dental alloys, as ground and oxidized for 1 min at 200〜800℃.
The adhesive strengths of resinous cements to precious alloys such as gold-platinum and gold-silver-palladium alloys were significantly increased by oxidation treatment. The most effective heating conditions were for 1 min at 400〜600℃. The effect of oxidation treatment to precious alloys was more remarkable in Panavia EX than in Super bond. For this reason, it seems likely that the adhesive monomer in Panavia EX strongly reacts with the copper-oxides formed on these alloys.
The oxidation treatment of the base alloys such as silver-indium and nickel-chromium alloys do not have this effect of adhesion of dental cements.
The shear adhesive strength of zinc phosphate cement increased by about 3 times by the oxidation treatment. However, the absolute value of adhesive strength was lowest among the all cements. The adhesive strength of polycarboxylate cement was not increased by oxidation treatment.

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The relationship between the polymerization reaction and chemical structure of dimethacrylates, and polymerizing temperature and atmosphere were investigated in a differential scanning calorimeter using an ordinary open aluminium pan.
The polymerizations were conducted in a nitrogen atmosphere and air at the temperatures of 70℃, 80℃, 90℃, 100℃ and 110℃ isothermaly. Five ethyleneglycol dimethacrylates, three alkyleneglycol dimethacrylates, urethane dimethacrylate (UDMA) and Bis-GMA were used.
The rates and extents of polymerization of all the dimethacrylates were affected by the monomer structure, and polymerizing temperature and atmosphere. For the dimethacrylates of ethyleneglycol, the polymerization rates decreased with the increase in number of chain members between two functional groups, while the extents of polymerization increased. Bis-GMA containing a framework of aromatic structure showed the lowest rates and extents of polymerization, and the dimethacrylates of long chain consists of aliphatic structure showed a tendency to attain higher extents of polymerization than the others. The rates and extents of polymerization increased with increase of polymerizing temperature, but the polymerizations of all the dimethacrylates were inhibited by oxygen in air. In the inhibition to the extents of polymerization, the monomers containing long chain members between two functional groups or high viscosity were fewer than the others.

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The objective of this study is to develop a new dental casting titanium alloy having a low melting point, good castability, and excellent mechanical properties. Twenty-five alloys from β-stabilized binary systems (Ti-Ag, Ti-Cu, Ti-Co, Ti-Cr, Ti-Fe, Ti-Mn, Ti-Pd and Ti-Si) and isomorphous binary system (Ti-Zr) were cast into the phosphate-bonded investment by using an argon arc melt/argon pressure casting machine. Castings of these alloys were evaluated metallurgically and by mechanical property testing. Ti-15 wt% Cr, Ti-12 wt% Mn, Ti-20 wt% Pd and Ti-50 wt% Zr were selected as basic titanium alloy systems. Castings of these alloys contained fewer casting defects, had high tensile strength, good ductility, and adequate hardness for the dental casting alloys. Microstructures of cast Ti-15 wt% Cr, Ti-12 wt% Mn and Ti-20 wt% Pd were observed to have retained β-titanium.The Ti-50 wt% Zr might have converted to α-titanium.

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Thermal expansion hysteresis (residual expansion or contraction) of 15 kinds of 88Au alloys to which Fe, In and/or Sn were added was measured to examine the cause of the deformation of the casting during the firing procedure.
High indium/low tin content alloys showed large hysteresis, and it increased during each heating and cooling cycle. Conversely, low indium/high tin content alloys showed small (sometimes negative) hysteresis, which decreased during each cycle. The hysteresis was hardly affected by the content of iron.
A linear relationship was shown between the thermal expansion hysteresis and the thermal expansion coefficients between 800-970℃ which were reported in the previous paper.

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The reaction process of an equimolar mixture of MgNH₄PO₄・6H₂O and NH₄H₂PO₄ was investigated by using the TG-DTA and X-ray diffraction method.
MgNH₄PO₄・6H₂O in the mixture decomposed above 80℃ through MgNH₄PO₄・H₂O to form an amorphous product in static air. In dried air flow, however, it directly decomposed above 70℃ to the amorphous phase without formation of MgNH₄PO₄・H₂O. On the other hand, NH₄H₂PO₄ also decomposed to an amorphous product after melting around 190℃. Both of the components were amorphous between 200 and 400℃. NH₃ and H₂O were gradually evolved from the amorphous mixture during the temperature. Magnesium tetrametaphosphate (Mg₂P₄O₁₂) crystallized completely above 400℃ from the amorphous mixture with evolving NH₃ and H₂O.
The reaction process in an isothermal condition was the same as that in the anisothermal condition described above, except for the formation of Mg(NH₄)₂H₂(PO₄)₂・4H₂O at 100℃ and MgNH₄(PO₃)₃ at 300℃.

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An alloy containing silver palladium together with less than about 5% gold content (hereinafter referred to as Ag-Pd alloy), is commercially available. Although this type of Ag-Pd alloy has mechanical properties comparable to those of 12% gold Ag-Pd alloy, and it is thought it can be used for clinical use, the effects of gold addition to Ag-Pd alloy remain yet to be known.
In view of those circumstances, by fixing the total of gold and palladium at 30 wt% and the total of copper and silver at 65 wt%, with the residual quantity 5 wt% of zinc, twelve kinds of (Au-)Pd-Cu-Ag-Zn alloys were melted and cast. The mechanical properties and resistances to tarnishing of each alloy during quenching and aging heat treatment were examined in order to make clear the possible effects of gold addition.
In respect of Cu/Ag and Au/Pd factors, the measuring values obtained were subjected to two-way layout orthogonal analysis of variance, and by seeking an orthogonal polynomial function concerning the significant term, isometric curves were drawn, thereby reaching the following conclusions:
1) The tensile strength at quenching treatment varies with the quantity of Cu/Ag, and the more the quantity of copper, the higher it becomes.
2) At aging treatment, the more the copper and gold content, the higher the tensile strength becomes.
3) Alloys containing 10 wt% of gold (20 wt% of palladium) and 15 wt% of copper (50 wt% of silver) show more than 20% of elongation at quenching treatment.
4) The brightness L^* after the tarnishing test becomes highest when the quantity of Cu/Ag is (13〜15)/(52〜50), and the larger the gold content, the higher the L^*.
5) That is, when the gold content of (Au-)Pd-Cu-Ag-Zn alloy with Au+Pd=30 wt%, is increased, elongation at quenching treatment increases, the ability of hardening at aging treatment increases, and resistance to tarnishing is improved.
6) Whithin the range of the experiment, it was found that the composition of alloy having the best properties was 10Au-20Pd-15Cu-50Ag-5Zn (wt%), and concerning palladium, copper and silver, the tolerance is ±2 wt%.

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Previously we reported the adhesiveness of the adducts of α-amino acid and methacryloyl chloride to teeth. The adducts were used with HEMA as UV-light cured bonding agents. DMTY (N, O-dimethacryloyl tyrosine) showed a good adhesiveness to the human dentin.
In this paper we report the syntheses of the new tyrosine derivatives, N-acetyl-O-methacryloyl tyrosine (AMTY) and O-methacryloyl tyrosine amide (MTYA), and their adhesiveness to the bovine dentin.
AMTY was prepared by the reaction of N-acetyl tyrosine with methacryloyl chloride in alkaline solution. MTYA was prepared by the reaction of tyrosine amide with methacryloyl chloride in trifluoroacetic acid.
The bovine dentin was etched by 10% citric acid-3% FeCl₃ solution. TBB-O was used as a polymerization initiator. The monomers were dissolved in MMA. The adhesiveness of DMTY and 4-META were also tested for comparison. The adhesive strengths were as follows: AMTY/MMA: 117±36; MTYA/MMA: 135±37; DMTY/MMA: 141±27; 4-META/MMA: 160±35 (kg/cm²).

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