Inlay restoration has an inherent drawback in pulp protection under temporary restoration.Leaky sealing may result in bacterial contamination of the cavity, possibly leading to pulpirritation.Liner Bond System(Kuraray)is unique in producing tight sealing film on the dentin surface with an adhesive bonding resin and a low viscosity composite, Protect Liner.It enables us to cover the prepared surface immediately after preparation to minimize further irritation to the pulp from mechanical, thermal, and bacterial insults during impression taking and temporary sealing.This study investigated the effect of five temporary filling materials on the adhesion of a luting composite to the liner.Cavit-G(ESPE), a water setting material, significantly increased tensile bond strength of the luting composite to the liner.Neither eugenol or non-eugenol materials affected the adhesion.Resin-based temporary filling materials, however, adhered to the liner surface and impaired bonding of the luting composite.The protect Liner surface in contact with temporary filling materials showed various morphological alterations and decreased surface hardness, which might suggest interaction between the liner and temporary filling materials.

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The measurement and comparison of surface roughnesses of both control and the impression, are useful for evaluating the reproducibility of impression materials by scanning laser microscope.This study, used two types of hydrocolloid impression materials;agar and alginate.Direct measurements of surface roughness were made by laser microscope 1LM21(Lasertec, Japan)and the surface roughness texture was evaluated.The control reference was the standard surface roughness plate.The Ra of agar were 0.350 to 0.378μm, the Rmax were 2.158 to 2.529μm, the Rz were 1.555 to 1.700μm.The Ra of alginate was 0.288 to 0.316μm, the Rmax was 1.484 to 1.718μm, and the Rz was 1.031 to 1.155μm.There was no significant difference between the control and agar for Ra and Rz, but a significant difference was demonstrated for Rmax by t-test(p<0.05).There was no significant difference between the control and alginate on Rz, but a significant difference was demonstrated for Ra and Rmax by t-test(p<0.05).We concluded that using laser microscope, the parameters of surface roughness and CCD images and computer graphics were useful for evaluating reproducibility of impression materials.

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Fabrication of titanium intracoronal attachments was investigated using both numerically controlled(NC)ram and wire-type electric discharge machining(EDM).The milling locus of titanium intracoronal attachments was designed on a personal computer according to the digitized data of the titanium cast crowns.Milling was performed on the titanium cast crowns which were prefabricated by a conventional casting method, using NC ram-type EDM with a simple cylindrcial electrode.The male was additionally designed to fit the female on a personal computer and fabricated from a titanium plate using wire-type EDM.The fabrication system developed in this study seemed to be a practical application of EDM to the manufacture of dental prosthetics.

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Visible light-cured resins were prepared by mixing three-types of composite photoinitiator compositions with six kinds of monomers to examine the chronological change during conversion.Cytotoxicity of the co-photosensitizer was also examined.Conversion showed the highest value when 8-quinoline-sulfonylchloride(8QS, 0.30%)was used as a cophotosensitizer.However, among the five kinds of monomers except TEGDMA, distinct differences in conversion were not recognized compared with dibenzoyl(DB, 0.15%)as a co-photosensitizer.Fifty percent inhibition concentration of cell proliferation(ID₅₀)was 11.4μg/ml in 8 QS and more than 3.4μg/ml in DB.

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The glod and palladium contents of Ag-Cu alloys have been standardized to 12 and 20wt%, respectively by all manufacturers.However, the contents of silver and copper vary from 45 to 55 wt% and from 10 to 20wt%, respectively, depending on the different amounts of silver and copper contents.Therefore, it is important to know the effect of silver/copper contents rate and the increase of gold contents not only for the alloy evaluation but also as a guideline for alloy development.This study investigated the relationship of heat treatment and strengthening of S-12 and Castwell M.C(12wt% Au-20wt% Pd-Ag-Cu alloy)to variations in the silver and copper contents of both alloys and to Alba 20 which contains 20wt% gold alloy(20wt% Au-Pd-Ag-Cu alloy).In 12wt% Au-20wt% Pd-Ag-Cu alloy, although Castwell M.C differs in silver and copper ratio from S-12, the characteristic curves representing the relationship between heat treatment temperature and mechanical properties were similiar.The strengthening mechanism of 12% Au-20% Pd-Ag-Cu alloys was induced by both age hardening and solid solution hardening, while that in the 20wt% Au-Pd-Ag-Cu alloy was only induced by the age hardening.

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Previous studies have shown that calcium phosphate cement(CPC), consisting of Ca₄(PO₄)O₂ and CaHPO₄, was highly biocompatible.This study evaluated the osteoconducitivity of CPC compared to that of a currently popular hydroxyapatite(HAp)based material(Apaceram)by implanting the materials in surgically formed pockets within the lower jaws of dogs.Two weeks after surgery, no inflammatory reactions were observed in tissue areas adjacent to either CPC or Apaceram, and the pockets were covered with dense fibrous connective tissues.Two months after surgery, the CPC filled pockets were covered with periosteum and bone tissues.The CPC mass in the pocket was partially replaced by newly formed bone.In Apaceram filled pockets, most of the interparticle spaces were filled with connective tissue and some with bone.At six months ofter surgery, the CPC filled pockets were completely covered with periosteum and thick cortical bone, and most of the CPC mass was replaced by bone.In the Apaceram packed pockets, the interparticle spaces were filled with periosteum and bone tissues, but these did not prevent outward movement of some of the particles.CPC showed superior biocompatibility and osteoconducitivity than the HAp material.

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To examine the effect of glass ionomer cement(HY10)which contains 10% Tanninfluoride preparation(HY agent)in the powder on inorganic phases of teeth, we applied it to synthetic hydroxyapatite(HAp)pellets which were then immersed in Hanks'balanced salt solution for 10, 30 and 90 days.Thereafter, the X-ray diffraction patterns, F, Zn and Sr uptake and acid resistance were studied.We used a glass ionomer cement(HY0)which does not contain the HY agent as a control.We recognized CaF₂ in the HY0 sample, and CaF₂ and zinc phosphate in the HY 10sample.F uptake of the HY10 sample was significantly higher than that of the HY0 sample, and increased over time.Zn uptake of the HY10 sample showed the highest value at 10 days and decreased over time, corresponding with the disappearance of zinc phosphate detected by the X-ray diffraction study.Sr uptake increased slightly over time.In the acid resistance test, the amount of Ca in the HY10 sample that had dissolved was significant less than that in the HY0 sample.Consequently, it was clear that HY 10 formed zinc phosphate and CaF₂ on the surface of the HAp pellets, and was superior to HY0 in the acid resistance.

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The present study investigated the effect of treating dentin with 2-hydroxyethyl methacrylate(HEMA)prior to application of a photocure bonding agent.The photocure bonding agent was composed of 0.5% camphorquinone(CQ)as a photosensitizer, 0.5% N-phenyl-glycine(NPG)as a reducing agent, 5.0% 2-methacryroyloxyethyl phenyl hydrogen phosphate(Phenyl-P)as an adhesion promoting monomer and 94.0% triethyleneglycol dimethacrylate(TEGDMA)as a base monomer.Bovine dentin samples were ground with 600-grid Carbimet paper discs(Buehler, USA), and demineralized with either aqueous solutions of 1, 5, 10, 20, 40 or 65% phosphoric acid.Improvement of bond strength depended on whether dentin treated with HEMA was rinsed.Without rinsing, improvement of bond strength was achieved even during contact of collagen with HEMA for 1min only.The effect of the 1min-HEMA treatment disappeared with rinsing on the tensile bond test.But even when rinsed, with HEMA treatment for 60min, improved bond strengths were achieved.When HEMA application followed phosphoric acid etching, a hybrid layer was demonstrated on SEM, and the bond strength increased to 6-7MPa.

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This study investigated ways to reduce the time reguired for dental casting.The properties of commercial gypsum bonded dental investments used in the quick heating method were tested.In comparison with a conventional cristobalite gypsum bonded investment, the properties obtained in the tested materials included:good fluidity, large dimensional changes during setting, thermal expansion because of quartz and cristobalite content, small thermal expansion values, and green strength ranging from 1.6-4.3MPa.There was approximately a 300℃ discrepancy between measuring points in the investment at quick heating.However, the surface of castings obtained using investments for quick heating were sound.For accurate casting, further studies are necessary, for example, concerning the start time of heating.

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To control hygroscopic expansion in alginate impression materials, 2, 5 and 10v/v% of ethanol was added to Povidone-iodine(PI)solutions.Dimensional changes were measured in four alginate impression materials and the surface roughness and waviness of stone casts were examined following post-impression application of the solutions by either immersion or spraying.The optimal amount of ethanol to add white maintaining dimensional stability in the cast surface was determined.The addition of ethanol was effective in reducing the expansion of alginate impressions in the PI solutions.The surface waviness of the stone casts depended on the dimensional change of impressions in the opposite directions.The optimal amount of etahnol to add in the 15 minute treatment was estimated as 7〜8% for immersing the impressions or 5〜10% for storing the impressions in a wet box following spraying.

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A new fatigue crack growth observation system was developed.In this system, a CCD video camera attached to a long distance microscope tracks the behavior of crack growth for the duration of the fatigue test.A 12% Au-Pd-Ag-Cu alloy and Type IV gold alloy were used in this fatigue test system.Both specimens were rolled in bars of 3×4×110mm and were tooled to form a 60°V notch 0.4mm deep in the 4mm side.All specimens received aging treatment at 400℃ for 30min.Fatigue tests were performed in cyclic tension-zero loading at a stress frequency of 60Hz.Fatigue crack growth in both alloy specimens were recorded on videotape and we obtained information on Ni, Nf, da/dN and ΔK.The fatigue strength relating to 10⁷ cycles of the both 12% Au-Pd-Ag-Cu alloy and Type IV gold alloy were approximately 35MPa and 52.5MPa respectively.Although the static properties for the two alloys were similar, their dynamic properties are quite different and the lacke of correlation between the static and dynamic strength became evident in the fatigue test.The fatigue crack of both alloys initiated from, the notch root area at 20% or more of the fatigue life.The fatigue crack propagation rate was influenced by the stress intensity factor range and by the alloy characterisitcs.

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We examined the formation mechanism of skin holes in titanium castings in silica investment molds.Possibly, phosphorus in the typical reaction zone came from magnesium orthophosphate, but magnesium was not detected in this zone.If reduction reactions produce metallic magnesium, it will vaporize rather than dissolve in molten titanium, because of its very low boiling point.Skin holes contaminated by magnesium, however, occurred in the vicinity of the area where magnesium orthophosphate was locally concentrated.The higher the mold temperature was, the greater the tendency became.The reaction of silica with titanium also caused the formation of skin holes.The inner surface was contaminated by silicon and oxygen, and a silicon-rich phase was observed.When phosphate-bonded and ethyl silicate-bonded investments were heated at temperatures above 1, 000℃, forsterite formed between the silica and magnesia.The reaction of forsterite with titanium caused the formation of slender holes along the mold wall.The area around them was contaminated by silicon and magnesium.Even if forsterite did not form in the burnout, it is likely that magnesia reacted easily with titanium under co-existence of silica, which caused the formation of skin holes.

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The elastic stiffness constants of two kinds of hydroxyapatite ceramics(OHAp, LiAp)were measured using the rectangular parallelepiped resonance(RPR)method.The OHAp ceramics were prepared from synthetic hydroxyapatite powder by sintering at 1, 200℃ for 1 hour, and the LiAp ceramics were sintered at 1, 050℃ for 10 minutes after adding a sintering agent of 2.8wt% Li₃PO₄ to the OHAp powder.The densities of OHAp and LiAp are 3.109 and 2.965g/cm³, respectively.The edge dimensions of RPR specimens were approximately 2 to 5mm.To elucidate whether some preferred orientation existed in the sintered body, the elastic stiffness constants C₁₁, C₁₂ and C₄₄ were determined independently, supposing that the specimens had a cubic symmetry.The results were C₁₁=149.5, C₁₂=57.4 and C₄₄=46.18 GPa for OHAp, and C₁₁=132.9, C₁₂=49.3 and C₄₄=41.97 GPa for LiAp.Because these values satisfy the isotropic relation, C₄₄=(C₁₁-C₁₂)/2 within experimental error, it was concluded that there were no preferred orientations introduced during the specimen preparation.The present measurements suggest that the RPR method is useful in measuring elasticity data on the dental ceramics because comparatively small specimens can be measured and the theoretical resonance frequencies can be calculated by personal computer.

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This investigation measured viscosity in various shear rates, environment temperature and mixing ratios, and our report discusses flow characteristics which are important properties in functional impression materials.Particle size distribution was examined by SEM and viscosity changes were measured by viscosimeter for six acrylic functional impression materials.From the finding of particle size distribution, two materials(HC, HS)contained particles over 100μm, and the other materials were composed of particles under 60〜70μm.From the viscosity findings, the apparent viscosity increased with the environment temperature rise in every materials.The six materials showed Newtonian viscosity or thixotropy.Furthermore, the Weissenberg effect was observed in two materials(HC, HS).

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The thermal properties of commercially available light-cured composite resins were measured under dry and wet(water sorption)conditions at room temperature.The thermal conductivity of the composites was about 0.3-0.8 Wm^-1K^-1.It was confirmed that the thermal properties of the composites were influenced by water sorption, but the effects were not simple, because the thermal properties were strongly affected by the composition and content of the filler.The thermal conductivity and thermal diffusivity of composites containing silica filler increased under wet conditions, compared to those under dry conditions.However, the thermal conductivity and thermal diffusivity on the composites whose fillers contained Zr etc., decreased under wet condition.

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The structure of calcium aluminosilicate glasses with selected composition was investigated using ²⁷Al and ²⁹Si nuclear magnetic resonance(NMR)and electron spectroscopy for chemical analysis(ESCA).In all glass specimens studied, Al was tetrahedrally coordinated by oxygen atoms.By resolving overlapped peaks in ²⁹Si NMR spectra, it was shown that the glass network was formed by up to four coexisting Q(m, n)(Si(OSi)_m-n;(OAl)_n(O^-)_;4-m)units and that a few specimens contained aluminum as neutral extra-network species.The peaks of Ols spectra obtained by ESCA were resolved into up to six peaks.The distribution of oxygen species obtained from the Ols spectra agreed with those calculated from the NMR spectra.Structural analysis of SiO₂-Al₂O₃-CaO glasses using MAS NMR was supported by ESCA and the glass structure was quantitatively determined.

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Layers of α-tricalcium phosphate plasma-spray-coated on titanium(α-TCP coated titanium)were characterized by crystal chemical methods, and their bone tissue reaction was histologically evaluated by canine implantation tests.The chemical properties of α-TCP coated layers were investigated by chemical analysis, density measurement, XRD, IR spectroscopy, SEM and TEM:moreover, in vitro solubility tests were carried out.A standard used for characterization was α-TCP powder prepared by heating β-TCP at 1, 400℃.The α-TCP coated titanium was successfully prepared from β-TCP powder using a plasma spray technique.The line-broadening of XRD profile showed that the α-TCP coated layers included an amorphous phase approximately 30-35% in weight with a crystallite size of 600Å.The SEM observation, bright field images of TEM, and electron diffraction patterns of halos and α-TCP spots revealed that the coated layers possessed a mosaic structure of 0.05-5μm grains and an amorphous phase.The chemical composition, density, and in vitro solubility test results suggested that the Ca/P ratio of α- TCP was 1.64 higher than 1.5 of stoichiometric α-TCP and the amorphous phase was similar to hydroxyapatite(HAp)in chemical composition and structure.The α-TCP coated titanium columns were implanted in femora and mandibulae of four mongrel dogs.The bone tissue reaction of the α-TCP coated titanium columns was investigated by histological observation and soft X-ray photographs, The bone bonding strength in femora was measured by pull-out test.HAp plasma-coated titanium columns served as controls.The bone bonding strength of α-TCP coated titanium columns was 0.4 times that of HAp coated titanium columns at 2-12 weeks after implantation, but increased to equal value at 48 weeks.The histological examination showed that the amount of new bone formation increased drastically in femoral bone marrow with dissolution of the α-TCP coated layers and that subsequently the α-TCP coated layers were replaced with new bone at the interface.From these results, α-TCP coated titanium can be used as a new hard tissue implant and the α-TCP coated layer is useful for bone-substitution.

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The marginal gap, setting shrinkage and shear bond strength to tooth structure were determined for recently available light-activated restorative glass ionomers.Three lightactivated glass ionomers and one composite were used.Investigations were performed immediately after light activation.In all cases, marginal gap was observed and an apparent correlation existed between marginal gap and setting shrinkage(r=0.9997, p<0.001).Marginal gap was influenced more by setting shrinkage than by shear bond strength.

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