This study examined the reproducibility of quantitative light-induced fluorescence to quantify an average fluorescence loss (ΔF), lesion area (ΔA) and mineral loss (ΔQ) in an artificial surface lesion permanent tooth and to investigate the ΔF, ΔA and ΔQ of each teeth with and without Nd : YAG laser irradiation after acid phosphate fluoride(APF) application during immersion into a remineralization solution for 10 days. The coefficients of variance of standard deviation (ΔF, ΔA and ΔQ) for 10 measurements were relatively small, and those ranges were 4.8% from 1.1%, indicating that good reproducibility was obtained. When teeth treated with APF solution. were soaked in the remineralization solution for 10 days, it was observed that remineralization of the lesion in the enamel surface was advancing slowly. In the case of Nd : YAG laser irradiation after APF application, gradually remineralization proceeded for 10 days starting from 2nd days after a rapid demineralization occurred within the initial 2 days.

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The electrodeposition of adhesive monomer on a dental metal surface was investigated to improve the adhesion of dental resin to dental metal. In this study, the application of commercially available adhesive dental cement liquid (SB solution) containing 4-methacryloxyethyl trimellitate anhydride (4-META) as the solution of electrodepositing was investigated in relation to the effect of current at various intensities and the effect of compositions of treatment solution for bond strength between light cured composite resin for crown-bridge facing and titanium. As a result, in the case of polished titanium (Ra<0.1μm), specimens showed the maximal values under the following treatment conditions : composition of treatment solution=3 : 1 : 3 (SB solution : water : acetone), treatment current=3mA/cm², shear bond strength was 8.3 MPa, and in the case of sand blasted titanium, composition of treatment solution=3 : 1 : 3, treatment current=3mA, shear bond strength was 18.8 MPa. Electrodeposition of SB solution was clearly an effective method for improving the bond strength between the dental metal and dental resin.

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This study investigated the relationship of CO₂ laser irradiation to morphological changes, physical properties (hardness and elastic modulus) and the chemical structure of the human tooth. A tooth was irradiated for 1min with a CO₂ laser at 0.5, 1, 2, 3, 4 and 5W (spot diameter of 0.4mm, distance of 10mm to the tooth). Although transpiration could not be recognized in the enamel and cementum after irradiation of 0.5W, morphological changes were observed at all other power levels. Regarding enamel, a morphological change in the horizontal direction was observed with increased irradiation power. Regarding dentine and cementum, morphological changes in the vertical direction were observed. There was no cracking of the enamel, but cracking was observed in dentin and cementum in all of cases. A decrease in the hardness and elastic modulus of enamel was observed at more than 2W, but those of dentin and cementum increased at levels up to 3W. Concentractions of calcium and phosphorus at the surface area of crater increased compared with those of the surrounding region that had not been affected by laser irradiation.

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The taper of the dowel post is supposed to act as a wedge on the root canal wall and a potential cause of root fracture. However, this wedge effect has not been clearly elucidated. Therefore, the effect of the tapered dowel post on root fracture was investigated. A post hole, with a taper of 1/10, 1/20, or parallel, was prepared, and the dowel post with the corresponding taper or parallel was inserted into the hole. Root fracture was caused by applying load to the post then both the fracture load and the fracture pattern were examined. The results indicated that the remaining tooth structure played an important role in the root fracture and that preparation of a post hole with a large taper easily caused root fracture.

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This study investigated whether paint containing a titanium-oxide based visible photocatalyst could be used to remove curry attached to denture base resins. Specimens made of denture base resin were dipped into the paint containing titanium oxide based visible photocatalyst, then immersed in curried solutions for eight hours. Thereafter, these specimens were exposed to visible light from a light-curing unit for 20 or 60 seconds. Colors of specimens were measured before and after exposure to visible light and the color differences were calculated. While the value of L^∗ was similar, the value of a^∗ increased and that of b^∗ decreased with extension of the exposure time. The color differences increased with extension of the exposure time. These results suggest that paint containing titanium-oxide based visible photocatalyst can be applicable to denture cleansing.

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