To improve the adhesion between silicone resilient liner and acrylic denture base, a novel adhesive was prepared.The monomer with a -SiH group which reacts with addition type silicone rubber was synthesized and was copolymerized with MMA.The copolymer solution in toluene was used as an adhesive.Silicone rubber was cured between acrylic resin rods on the end of which the adhesive had been applied.After the bonded specimen was kept in 80℃ water, the tensile bond strength was measured to evaluate the water durability of the bonding.The tensile bond strength of the specimens on which the adhesive had been applied at varions concentrations showed the tendency to increase as the concentration of the adhesive increased up to around 10wt%.The tensile bond strength of the specimens kept in 80℃ water did not decrease substantially after 14 days.The adhesion of the silicone rubber and acrylic resin showed excellent durability against hot water.It was concluded that the silicone denture liner with high bonding durability could be developed by the application of this adhesive.

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Thermal diffusivity, specific thermal capacity and thermal conductivity of 14 products of dental cements widely used in clinical practice were examined;glass ionomer cement, polycarboxylate cement and aluminate cement;under three temperatures of 0, 37 and 60℃, by the xenon flash method.The relationship among thermal properties, the composition of cements and the particle size of cements were also studied.Thermal diffusivity showed the maximum value at 0℃ and it decreased as the temperature increased.Specific thermal capacity showed the maximum value at 60℃ and it increased as the temperature increased.Thermal conductivity showed the maximum value at 0℃ and it decreased as the temperature increased.When the amount of Zn, Mg, Al and Si included in cement powders was large, thermal diffusivity and thermal conductivity increased but specific thermal capacity decreased.When the particle size of cement was small, thermal diffusivity and thermal conductivity increased but specific thermal capacity decreased.

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Adhesive properties of composite resin to calcium sulfate dihydrate crystal growth-treated human dentin, its calcium being derived from hydroxyapatite in dentin, were evaluated from morphological changes of dentin stuctures, shear bond test and fractography of its fractured surfaces.By the crystal growth treatment of dentin covered with a smear layer, dentinal plugs were left protecting dentinal tubules and the etching of intertubular and peritubular dentins were reduced, as compared with acid-etched dentin.The bond strength of composite resin to the crystal growth-treated dentin was not statistically different from that of composite resin to acid-etched dentin(p<0.05).

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Studies were undertaken to apply the automatic CAD/CAM system to dentistry and prosthetic appliances.In this Dental CAD/CAM system, two types of data were handled, the inner data of the crown, taken by the LASER-scanning of the preparpared tooth, and the outer data of the crown, modified the CAD Data Base, which is taken with the three dimensional point digitizer(3DPD).The inner data are the points data situated on the mesh positions.In the outer data, the measured points are not arranged on the meshed positions because they are intended to pick up the important points morphologically and occlusionally.The outer point data is interpolated by the spline function, and then the data are presented by the interpolated coefficients.Mathematically, it is very difficult to combine these data on the cervical margin because of the different data structures.We propose that by digitizing the prepared tooth margin with 3DPD, marginal line data for the outer data can be obtained.

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A soldering technique was developed for titanium and titanium alloy.As a heatsource, infrared radiation from a halogen lamp was used.Titanium, gold and silver base solders were evaluated.The conditions studied were;ambience, gap distance, heating time, location of solder, investing method, pre-heating temperature and wrought or cast test metal.The ultimate tensile strength of each soldered joint was evaluated with a universal testing machine.Under flushing argon gas ambience, titanium, gold and silver base solders were successful.However, only silver base solders were successful in atmospheric ambience.The gap distance was not significant up to 300μm.To ensure the solder joint, the investing method required pre-heating to 500℃ and pickling by acid.There was no significant difference between wrought and cast metal specimens.

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Super-elastic NiTi alloy wire has special properties, i.e;shape memory effect, super-elasticity and spring-back property.Heat treatment is required to bend the super-elastic NiTi alloy wire and to control its super-elastic force value.The conditions of heat treatment for the forming of super-elastic NiTi alloy wire for use in removable orthodontic appliances were determined.After 90 minutes of heat treatment at 450℃(first stage of heat treatment), the load decreased and it became shape memory wire.By the second stage of heat treatment the same sample needs to be formed into a required shape so as to restore the original mechanical properties.The higher(510℃〜520℃)the heat treatment temperature was, the shorter the required time.On the contrary the lower(480℃〜490℃)the temperature was, the longer the required time.However, when the temperature exceeded 530℃, the excellent properties of NiTi alloy wire were lost.In conclusion, the optimum temperature of the second heat treatment was 480℃〜520℃ and load of the shaped wire could be changed according to the different heat treatment conditions.Therefore, the force level can be controlled for various orthodontic appliances.

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The adhesive bonding of resin jacket crown to the luting cement was examined.The bond strength between cured opaque resin and luting cement was evaluated.The effect of various surface treatments for cured opaque resin was also investigated.Light-cured opaque resins used were Dentacolor(Kulzer), Thermoresin LC(GC), New Metacolor L(Sun Medical)and Cesead(Kuraray).Four luting cements, Elite Cement 100(GC, EC), Fuji Ionomer Type I(GC, FI), Super Bond C&B(Sun Medical, SB)and Panavia EX(Kuraray, PE)were used.The cylindrical bilayered specimens made of light-cured opaque resin and veneering resin(Dentacolor DA10)were prepared in the Dentacolor XS unit.Two types of specimens for shear bond test, cured opaque resin-cured opaque resin joined and cured opaque resin-sandblasted Au-Ag-Pd alloy(Morita)joined with luting cement, were prepared.In the case of cured opaque resins being bonded together with luting cement, several kinds of surface treatments were performed.As a result, cured opaque resins were wiped with an alcoholic tampon and applied Clearfil Porcelain Bond(Kuraray, A1+PB)showed significantly higher bond strengths than untreated cured opaque resins with three luting cements except for EC.Cured opaque resins with A1+PB showed 0MPa with use of EC, and nearly 20MPa by the use of FI.On the other hand, all the specimens surface-treated with A1+PB showed a MPa 30 or more with SB and PE.Moreover, these specimens showed adherent failure within the veneering resin.Cured opaque resins were surface-treated with A1+PB and joined to Au-Ag-Pd alloy with luting cement had also higher bond strengths and more excellent adhesive durability than untreated cured opaque resins.These findings suggest that the Al+PB surface treatment improves the shear bond strength of cured opaque resin to the luting cement, and that this surface treatment may be effective for cementation of the resin jacket crown in prosthodontic practice.

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This paper reports the micro structure and the elemental maps of some internal defects in the titanium casting, formed by reactions with the investment inclusion.The defect, without a hole or with an irregular or a circular hole, accompanied the oxygenstabilized α phase and the acicular structure corresponding to the oxygen content distribution.Silicon and aluminium, occasionally phosphorus and magnesium, existed in and around the defect;the micro structure was similar to the layered structure of the casting surface.The defect, especially the oxygen-stabilized α phase, played an important role in the source of crack initiation.Probably, some of the observed cracks were formed through the plastic bending deformation of the casting, and the others, through the cooling process of the casting.

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The relationship between additional pressure after injection molding and the adaptability of denture base was determined.When pressure of about 60kgf/cm^2 was applied to the dough for 1 minute, the dough was completely injected in to the mold space.Fastening of sprue with stoppers of φ8×5mm and φ8×10mm at a pressure of about 10kgf/cm^2 after injection molding made the pressure of the dough increase to about 35 and 50kgf/cm^2, respectively.When the vent in the denture flask was fitted with a stopper, the resin base denture constructed without additional pressure after injection molding had an adaptability superior to that constructed with compression molding.The adaptability of the resin base denture constructed under additional pressure after injection molding was 30〜50% superior to that constructed with compression molding.

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The bonding of photocurable resin composites to dentin and enamel treated with various pretreatment solutions was evaluated.The used solutions were 0.5mol/L EDTA disodium salt[EDTA5-0(Na)](pH7.4), 0.3mol/L EDTA disodium salt-0.2mol/L EDTA sodium iron salt(pH7.4)[EDTA3-2(Na/Fe)], 0.5mol/L EDTA diammonium salt[EDTA5-0(NH_4)](pH7.4), 0.3mol/L EDTA diammonium salt-0.2mol/L EDTA ammonium iron salt(pH7.4)[EDTA3-2(NH_4/Fe)], 10% citric acid(10-0), 10% citric acid-3% ferric chloride(10-3)and 65% phosphoric acid(H_3PO_4).The high bond strengths to dentin were obtained using EDTA3-2(Na/Fe), EDTA3-2(NH_4/Fe)and 10-3.H_3PO_4 pretreatment gave the highest bond strength to enamel.These findings support the fact that ferric irons in the pretreatment solutions markedly affected dentin bonding, while the amount of demineralized enamel with the pretreatment solutions directly influenced on enamel bonding.

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