To clarify the role of polymerization initiator in dentin bonding, tributylborane(TBB), barbituric acid system, and BPO / amine initiators were studied for polymerization of PMMA / MMA resin at the dentin interface by FT-Raman spectroscopy. Moreover, the influences of combined use of the initiators on polymerization of the resin and dentin bonding were also examined. Polymerization at the dentin interface was promoted by TBB and barbituric acid system when dentin was treated with the conditioners effective for bonding. Initiators capable of promoting polymerization at the dentin interface tended to produce high bond strength. The combined use of TBB and barbituric acid system or BPO / amine produced desirable effects on polymerization of the resin but different effects on the bond strength depending on the combination with TBB. The combined use of BPO / amine with TBB suggested that it can improve the performance of MMA-TBB resin currently in clinical use.

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Dental alloys(Au-Ag-Cu ternary system alloy)for filling have been immersed in two kind of high oxidation potential water and three kind of functional water with high chlorine density. We examined here, the effect of immersion on color, weight of alloys, pH, oxidation-reductive potential(ORP value)and dissolved chloride density in liquids. The following results were obtained : Following immersion in OMCO-5.5, the color difference was large especially for pure silver measuring 41.3. The weight, silver contained alloys was increased, but that copper contained was decreased. The combination of functional water with high chlorine density and silver contained alloys, high oxidation potential water and copper contained alloys caused a large pH change. The ORP value and dissolved chloride density in liquids, in case of gold contained alloys kept high level, but silver or copper contained alloys kept low. The dissolved chloride density in liquids kept high level functional water with high chlorine density than high oxidation potential water.

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In a previous study, dentures processed with injection type microwave-curing resin and conventional type microwave-curing resin showed different dimensional accuracy. The purpose of this study was to elucidate the variables that exert the influence on dimensional change. The variables of denture base material, investment material, molding technique, microwave exposing time and bench cooling time were analyzed with robust design methods, and the conditions imposed in the study were compared. The variables affected dimensional accuracy for complete denture processed with microwave-curing resin were denture base material, investment material and microwave exposing time.

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Assuming that teeth and alveolar bone were rigid bodies and the periodontal ligament was an elastic membrane, the initial mobility of the upper and lower teeth was calculated. The degree of tooth mobility was shown as fundamental data. In general, mobility decreases with the surface area of the root. The mobility about mesio-distal axis(t axis) θ_t / M_t is almost proportionally inverse to the surface area. The mobility also depends on the root configuration. The meiso-distal mobility δ_t / P_t is smaller than the bucco(labio)-lingual mobility δ_n / P_n because the thickness of the root h is greater than the width w. In the case of molars and the upper first premolar, which have two or three roots, the mobility about vertical axis(z axis)θ_z / M_t was very small. On the other hand, θ_z / M_t of the upper second incisor, which has a root with a circular cross section, became very large.

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In order to prepare surface treatment agents for both precious and nonprecious metal alloys, an adhesive bonding promoter for noble metals, 9, 10-epithiodecyl 4-vinylbenzoate(EP 8 VB), and one for base metals, 4-methacryloyloxyethoxycarbonylphthalic anhydride(4-META), were dissolved in dehydrated benzene. Precious and nonprecious metal alloys and pure titanium were used as an adherend. A surface treatment agent was applied to the surface of alloys polished to a mirror-like finish and allowed to stand for one day. The surfaces were washed to remove excessive monomers prior to bonding. Two alloy specimens were buttjointed with MMA-PMMA resin and then the tensile bond strengths were measured after 2,000 thermal cyclings. The surface treatment with both EP 8 VB and 4-META significantly enhanced the bond strengths to nonprecious metal alloys and titanium compared with EP 8 VB. On the other hand, the bond strengths to precious metal alloys slightly decreased by adding 4-META to surface treatment agents containing EP 8 VB.

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The effects of heat sterilization of hydrophilic vinyl silicone rubber impressions with various thicknesses on the reproducibility of stone models were investigated. An epoxy resin mold to simulate a full-crown preparation with adjacent teeth and three perforated metal trays with impressions adjusted to thicknesses of 1, 3 and 5 mm were used. Impressions were sterilized in a conventional steam autoclave and a chemical vapor sterilizer. The stone models obtained from the hydrophilic vinyl silicone rubber impressions sterilized by heat showed dimensional change and deformation. Those effects on the reproducibility varied depending on the thickness of the impression.

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Thermal expansion coefficients were determined using a dilatometer on commercial dental porcelains, stoichiometric tetragonal leucite, cesium added cubic leucite, three types of glass, and mixtures of leucite and glass. Thermal expansion coefficients of leucite were also derived from the lattice parameter changes using high temperature X-ray diffractometry. The thermal expansion behaviors of dental porcelains were mainly affected by the thermal expansion behavior of the glass, which constructs the glass matrix in the fired porcelains, although leucite transforms between tetragonal and cubic in the temperature range of 600〜650℃ with a large volume change. These results suggest that the glass surrounding leucite particles is required to have a higher glass transition temperature than 650℃ because of high stress in the surrounded matrix glass.

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The purpose of this study was to investigate the influence of various fillers on the frictional wear of photo-cured composite resins. The specimens were prepared from three experimental composite resins that contained irregular silica(I-CR), spherical silica(S-CR)or microfilled silica(M-CR), and a commercial one with a hybrid type filler. The coefficient of friction between the abrasion and the specimen was determined by the frictional wear device with a rotating wheel. After that test, the depth of wear was measured and the wear surface was observed by SEM. Therefore, although S-CR had the same coefficient of friction as I-CR, the depth of wear in S-CR was higher than that in I-CR. The failure of S-CR was observed on the wear surface compared with other composite resins. It was considered that the composite resin contained with spherical silica had a differential wear mechanism from that with irregular silica.

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Measuring system of length or location in coordinates was discussed using different object locations of two images obtained before and after parallel shifting of the optical axis in extreme close-up photography with dentition. The sizes of the objects and the distances between the objects and lenses in three dimensional coodinates were measured based on the paraxial ray theory of geometrical optics with computer processing. The following results were obtained : (1)The ratio(R₁)of converting dimensional scales in an image screen to actual geometrical dimensions was known to be constant using the expression with the focal length and the distance of the object. By using the ratio(R₁), the exact process of measuring the lengths and locations were secured. (2)The exact amount of dental arch width and dental arch length of dentition was aquired by computer processing images obtained using extreme close-up photograhy.

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This study was undergone to find the cause of crack growth of denture-based heat cured resin. By measuring the crack growth of precracked specimens in the three point bending constant load test, the effects of environmental solutions(ethanol, acetic acid, lactic acid, citric acid, acetone, NaCl, ascorbic acid and distilled water)and their concentrations were investigated. The results suggested that these solutions, in addition to stress would participate in the crack growth of the denture base. Considering that both ethanol and acetic acid had especially great effects, it was determined that alcoholic drinks and dishes with vinegar promote crack growth. Furthermore, the crack growth rate reduced with time in other environmental solutions because the stress was dispersed by many microcracks formed around the main crack. It was considered that these cracks would from new starting points for crack growth with increasing load.

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