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The purpose of this study was to evaluate the influence of visible-light exposure on water absorption, solubility and colour stability of dual-curable luting composites. Using eight dual-curable luting composites (2bond2, Bistite II, G-CERA Cosmotech II, Imperva Dual, Linkmax, Lute-It, Panavia Fluoro Cement and Variolink II), disk specimens were prepared by the following two methods: (i) dual-cured specimens; exposed with visible-light from a light-curing unit, and (ii) chemical-cured specimens; chemically polymerized without exposure. Five specimens were produced for each material and curing mode. Water absorption and solubility were determined according to standardized testing methods, and the data were compared using analysis of variance (ANOVA) and contrasts. With regard to colour stability, the colour difference (DeltaE*) values between 24 h and the other immersion periods (1, 2, 3, 4, 8, 12, 16, 20 and 24 weeks) were calculated and then analysed by repeated measure ANOVA. The dual-cured specimens exhibited significantly lower solubility values than the chemical-cured specimens except for the Lute-It material. The dual-cured Linkmax material exhibited the lowest solubility (0.51 +/- 0.01 microg mm(-3)) and the lowest DeltaE* value after 24 weeks (2.64 +/- 0.39). The dual-curable luting composites should be light-exposed after seating of restorations in order to reduce water absorption and solubility, and to improve colour stability.

This study was conducted to evaluate influence of visible-light exposure on colour stability of dual-curable luting composite. Using six dual-curable luting composites [Bistite II (BI), Clapearl DC (CL), Dicor Light Activated Cement (DI), G-Cera Cosmotech II (GC), Lute-It (LU) and Variolink II (VA), disk specimens were prepared with the following two methods: (i) dual-cured specimens, exposure with visible-light from a photo-curing unit for 120 s and (ii) chemical-cured specimens, chemically cured without exposure. Five specimens were produced for each material and curing mode. After 24 h, all specimens were immersed in distilled water at 37 degrees C for 24 weeks, during which colour accuracy was measured with a dental colorimeter. The colours characterized in the Commission Internationale d'Eclairage (CIE) L*a*b* colour space were first determined 24 h after preparation (baseline colour evaluation), and again after 1, 2, 3, 4, 8, 12, 16 and 24 weeks. The colour difference (Delta E*) values between 24 h and the other immersion periods were calculated, and then analysed by repeated measure analysis of variance (ANOVA). In addition, the Delta E* values after 24 weeks for dual-cured specimens were compared with those for chemical-cured specimens by one-way ANOVA and by contrasts for each composite (P < 0.05). The Delta E* values were influenced by the material and curing mode as well as immersion period (P=0.0001). After 24 weeks the dual-cured specimens showed significantly lower Delta E* values than the chemical-cured specimens, except for the VA material. The CL material exhibited the least colour change (1.9 +/- 0.2) among the dual-cured specimens, and the VA material showed the least (4.5 +/- 0.9) among the chemical-cured specimens after 24 weeks. Dual-curable luting composites should be polymerized with the dual modes to ensure colour stability.

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A high-intensity laboratory photo-curing unit has been developed with the aim of improving the post-curing properties of composite veneering materials. This study introduces the structure of the curing unit and examines the resulting properties of a representative composite material. The curing unit is equipped with two metal halide lamps that radiate both ultraviolet and visible light. Unlike conventional metal halide lamps for industrial use, these metal halide lamps radiate an increased intensity of visible radiation. Properties of a microfilled composite veneering material cured with the new metal halide unit were ascertained. A xenon photo-curing unit was also used as a control. The specimens cured with the metal halide unit exhibited greater Knoop hardness numbers and flexural moduli as compared with those cured with the xenon unit, and also showed reduced water solubility values. These results suggest that the metal halide light source is effective in curing composite materials within a shorter period of time and with improved conversion.

The purpose of the current study was to evaluate the clinical performance of a chemically cured denture relining material after 1-year service period. A powder-liquid material designed for denture base relining (Tokuso Rebase Normal-set, Tokuyama Corp., Tokyo, Japan.) was assessed. Fifty adult patients, who required denture reline treatment, participated in the current project. Adaptation of each denture was examined with a silicone elastomeric material, and the surface to be relined was reduced by means of a rotary cutting instrument, then conditioned with dichloromethane. The relining material was spatulated, poured into the relining area, inserted and adjusted after setting. Each relined denture was subjected to base line evaluation immediately after relining and end evaluation after 1 year. Standardized criteria were used for direct evaluation of the material. After an observation period of 1 year, the rate of the relining cases considered to be in clinically ideal condition (Alfa) was 90% for staining, 90% for discoloration, 94% for peeling, 96% for adaptation and 100% for irritation to oral tissue. Only one case was judged as clinically unacceptable (Charlie), and this was for staining. On the basis of a 1-year observation, the Tokuso Rebase material is considered to be a clinically reliable hard denture relining agent.

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