The purpose of this study was to compare the tensile bond strengths (TBSs) and failure mode of 4-META/MMA-TBB resin to 60°C-heated and unheated bovine dentin, especially to investigate the influence of ferric chloride contained in citric acid pre-conditioning. In addition, the effect of HEMA priming for heated dentin was also evaluated. The TBSs to heated dentin were significantly lower than those to unheated dentin. Adhesive failures were observed in most specimens of the heated and HEMA-non primed group. HEMA application to heated dentin significantly increased the TBSs in each acid conditioning, which were also significantly higher than those of the unheated and ferric chloride-contained citric acid-conditioned group. It was clarified that heating dentin decreased the bond strength without HEMA priming even if the dentin surfaces were acid conditioned with 10-3, while HEMA priming after acid conditioning recovered the bond strength.

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Age-hardening characteristics in a dental low-gold alloy composed of 40.0wt% Au-35.0wt%Ag-7.9wt% Pd-7.0wt% Cu-5.0wt% In-3.5wt% Zn-1.5wt% Sn, were investigated by means of the hardness test, XRD study, SEM observations and EPMA. The following results were obtained.
The age-hardening was characterized by a precipitation of Cu-rich α₂ phase in the α phase. The softening that occurred following prolonged ageing was due to the heterogeneous formation of the fine nodular precipitates composed of the Ag-rich α₁ phase and the Cu-rich α₂ phase at the grain boundaries of the α phase.

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The purpose of this study was to assess the effects of systemic zinc sulfate in the treatment of recurrent aphthous stomatitis (RAS) by atomic absorption spectrophotometry. The study was carried out on 40 patients with RAS. The first group consisted of 20 subjects with RAS who were administered zinc sulfate (220mg) once per day for one month. In the second group, there were 20 subjects with RAS who were administered placebo (saccharose). Results showed that the levels of serum zinc before treatment were under the normal value in the 42.5% percent of the patients with RAS. Saliva ALP, serum zinc, serum albumin, and serum alkaline phosphates activity for group II were significantly lower than those for group I after treatment (p<0.01). After 1 month of zinc therapy the aphthae reduced and did not reappear for 3 months. The empirical use of systemic zinc sulfate supplementation in the treatment of RAS is recommend.

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This study investigated the effect of the number and position of woven glass fibers in denture base resin matrix on its impact strength. Test specimens were reinforced with woven glass fiber 0.5, 1.0, or 1.5mm below the surface. The impact strength was tested using an Izod-type impact tester with an impact speed of 335cm/s, which simulates dropping the denture, and using a flywheel-type impact tester with a two-point support at 13.5 and 75.0cm/s, which simulates the chewing. The woven glass fibers had a strengthening effect in all tests, and the impact resistance was further improved when the woven glass fibers were positioned more superficially in the resin. The results suggest that woven glass fiber is an effective reinforcement in denture base resin.

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The purpose of this study was to evaluate the effect of dentin depth and tubule direction on the ultimate tensile strength (UTS) of human dentin. Dentin slabs of 0.5-mm thickness were trimmed either from the mesial and distal (for specimens with the tubules parallel to the tensile force; parallel group) or from the occlusal and pulpal surfaces (perpendicular group) to reduce the cross-sectional area of the superficial, middle, and deep regions to 0.25mm², and subjected to microtensile testing. From SEM photomicrographs of the fractured specimens of the parallel group, the tubule density was investigated. For both parallel and perpendicular groups, superficial dentin showed a significantly higher UTS than deep dentin. The tubule density of superficial dentin was significantly lower than that of middle and deep dentin. When performing the microtensile bond test to deep dentin, it is possible that cohesive failure of dentin can occur at relatively low tensile stresses.

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The effects of dual use of tributylborane (TBB) and benzoyl peroxide/N, N-dimethyl-p-toluidine (BPO/DMPT) or camphorquinone/N, N-dimethyaminoethyl methacrylate (CQ/DMAEMA), as well as BPO/DMPT and CQ/DMAEMA for comparison purposes, on postpolymerization of PMMA/MMA resin were examined from the view point of long term changes of residual MMA and molecular weight. Each resin was polymerized and analyzed by high performance liquid chromatography and size exclusion chromatography. The effect of dual use of TBB and BPO/DMPT or CQ/DMAEMA on polymerization of PMMA/MMA resin was additive in nature and each initiator system worked rather independently without little interaction between the two. TBB was effective especially during the period of postpolymerization. On the other hand, BPO/DMPT used in combination with CQ/DMAEMA had a limited effect only during the initial period and little effect during postpolymerization. It was suggested that TBB was most suitable as a chemically accelerated initiator component for a dual cure system.

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The purpose of this study was to evaluate the usefulness of autofluorescence of carious lesions on caries diagnosis. The observation of the micromorophology of caries lesions was conducted using a confocal laser scanning microscope, a fluorescence microscope and a WDX type electron probe X-ray microanalyzer. Observation of autofluorescence under Cy5 and UV fields showed clearly specific images of autofluorescence in the carious lesion. However, observation of autofluorescence under FITC field showed images of autofluorescence with unclear boundaries in the carious lesion. EPMA images showed decreases in Ca and P in the carious areas. As a result of the observation of autofluorescence and the EPMA images in the carious lesion, a correlation was noted between autofluorescence under the Cy5 field as the laser fluorescence apparatus for caries diagnosis and demineralized areas. The usefulness of autofluorescence of carious lesion on caries diagnosis was suggested.

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The purpose of this study was to examine the application of an ultrasonic pulse-reflection technique for the evaluation of adhesive defects. First, the sonic velocities in the enamel and dentin of human molars and bovine incisors were measured with a pulsar receiver attached to an ultrasonic transducer. The identification of the dentino-enamel junction and pulp-dentin interface using the ultrasonic method based on intrinsic sonic velocities showed good agreement with the actual measured thicknesses. Next, a cemented restoration with artificial faults was prepared. Half of the Au-Ag-Pd alloy plate area was cemented to the dentin slab using luting resin cement. The adhesive interface was evaluated with a high-resolution ultrasonic imaging system. Clear internal faults were evident from the ultrasonic tomogram. The findings of this study suggest that the ultrasonic pulse-reflection technique may be useful for inspecting and imaging structural defects of adhesive interfaces.

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The purpose of this study was to investigate the contact probes of Er: YAG laser before and after tooth ablation. Three kinds of contact probe were prepared. The first was an unused probe (NE). The second was used to prepare 10 cervical cavities (KP). The third was a probe that was judged for an exchange by three dentists who had expertise with Er: YAG laser (EX). The surface observation and mapping analysis were performed. The contact surface of NE was a flat and smooth surface, only Si was observed. KP demonstrated an uneven surface, Si was observed throughout, with scattered indications of Ca and P. EX displayed regions of fracture along the edge and a surface exhibiting dissolved adherents in parts. It was suggested that micro-explosions have effects on not only the tooth substance, but also the contact surface of the probe.

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The objective of this study is to develop a casting investment that prevents the blackening of the cast surface of noble metal alloys. The experimental investments were prepared using a gypsum-bonded investment in which the metallic powders such as boron (B), silicon (Si), aluminum (Al) and titanium (Ti) were added as oxidizing agents. An Ag-Pd-Cu-Au alloy was cast into the mold made of the prepared investment. The effect of the addition of each metal powder was evaluated from the color difference between the as-cast surface and the polished surface of the cast specimen. The color of the as-cast surface approached that of the polished surface with increasing B and Al content. A lower mean value in the color difference was obtained at 0.25-1.00mass% B content. B and Al are useful as an additive in a gypsum-bonded investment to prevent the blackening of an Ag-Pd-Cu-Au alloy. The effects of Si and Ti powder addition could not be found.

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The ions released from conventional and high-copper amalgams in contact with titanium were quantitatively analyzed in a 0.9% NaCl solution at 37°C when the surface area ratio of titanium/amalgam was set up as 1/10, 1/1, or 10/1. The corrosion potentials of the amalgams and titanium were measured under the same conditions. Surface analyses on the amalgams were also employed using SEM with WDS. Though the potential of the conventional amalgam was always lower than that of titanium, that of the high-copper amalgam was reversed during the early stage of immersion and remained lower. When the surface area ratio of titanium grew at 10/1, tin and copper ions released from the conventional and high-copper amalgam, respectively, increased significantly compared with those of each amalgam that was not in contact with titanium. The galvanic corrosion in such a large surface area of titanium possibly led to the heavy corrosion of the amalgams.

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