Color stability of indirect composite materials polymerized with different polymerization systems.

The purpose of the current study was to evaluate the color stability of two indirect composite materials (Sinfony and Pearleste) polymerized with different laboratory polymerization systems. Disk specimens were prepared with their proprietary polymerization systems (Visio and Pearlcure systems) or with a metal halide light polymerization unit (Hyper LII) for 60, 120, and 180 s. After storage at 37 degrees C for 24 h, the specimens were immersed in either purified water or tea. Color change between baseline evaluation and after 4 weeks was determined with a dental chroma meter (ShadeEye NCC) using black and white backgrounds. CIE 1976 L(*)a(*)b(*) values were determined, and they were converted into DeltaE(*)(ab) values. The DeltaE(*)(ab) value of the Sinfony material immersed in tea was the highest when the material was polymerized with the proprietary Visio system. The Pearleste material immersed in purified water and tea was not affected substantially by the polymerization systems. Among the 12 groups polymerized with the Hyper LII units, DeltaE(*)(ab) values of 11 groups were significantly lower for the Pearleste material than for the Sinfony material. It can be concluded that the Pearleste material was stable against color change when the material was polymerized with either the Pearlcure system or with the Hyper LII unit.

Bond strength to bovine dentin of a composite core build-up material combined with four different bonding agents.

Clearfil DC Bond (DC) is a new single-step, dual-cure bonding agent. In this study, the shear bond strengths of a core build-up composite to dentin used with four bonding systems [DC, Unifil Core Self-Etching Bond (UC), Clearfil SE Bond (SE) and Cleafil tri-S Bond (TS)] were measured. The bonding ability after 7 days of storage and in vitro durability following 20,000 thermocycles were also evaluated. The bond strength of DC did not differ significantly from those of other bonding systems after 24 hours of storage. Another dual-cure bonding system, UC, showed a significant reduction of bond strength after 7 days of storage. On the other hand, the bond strength of TS, a light-cured bonding system with a similar composition to DC, was reduced significantly following 20,000 thermocycles. SE, a two-step light-cure bonding system in the same series as DC, provided superior bond strength under all conditions. Although DC showed a slightly lower bond strength than SE, there was no significant difference between DC and SE under all conditions. Consequently, DC may be a useful and effective bonding system for multiple composite resin restorations.

Influence of abutment materials on the resultant color of heat-pressed lithium disilicate ceramics.

The purpose of this study was to evaluate the influence of abutment materials on the color of IPS Empress 2 ceramic coping with different thicknesses. Ceramic coping specimens (12.0x12.0x0.8-2.0 mm) were fabricated from IPS Empress 2 material (Ingot-100, n=5/group). Abutment specimens were fabricated from a build-up composite, a gold alloy, or a silver-palladium alloy. Color was evaluated using a colorimeter according to the CIE L*a*b* system. The L*a*b* values of the ceramic coping specimens of different thicknesses on each abutment specimen were measured. Following which, the color difference (deltaE*ab) values between the ceramic coping specimens on various abutment specimens were calculated. Significant differences in deltaE*ab value were observed among different abutment specimens at certain ceramic coping thicknesses (P<0.05). Thus, it was concluded that the color of IPS Empress 2 coping material was influenced significantly by both the thickness of the coping and the color of the abutment material.