Changes in chroma of two indirect composite materials polymerized with different polymerization systems

Evaluation of color stability and microhardness of contemporary bulk-fill composite resins with different polymerization properties

OBJECTIVES

To determine the color stability and microhardness of three bulk-fill composites with different polymerization characteristics, after immersion in four different solutions.

MATERIALS AND METHODS

Color measurements of three bulk fill (Viscalor (VIS), Tetric PowerFill (TPF), Fill Up! (FUP)) and a microhyrid composite resin (G-aenial posterior [GCP]) were performed after polymerization. The specimens were immersed in coffee, cola, red wine and distilled water. Discolorations were recorded after 24 h (T1), 10 days (T2) and 30 days (T3) of immersion. ΔE (CIEDE2000) values were calculated. Vickers microhardness (VHN) was measured from top and bottom surfaces at T0 and T3. Data was analyzed with Two-way ANOVA, One-way ANOVA and Tukey post hoc tests.

RESULTS

The highest discoloration was seen in wine and the lowest in distilled water and cola. At T3, there was no difference in distilled water groups, while the statistically highest ΔE₀₀ were obtained in TPF and GCP in coffee, cola and wine. VIS groups had the highest VHN values at T0 and T3 in all solutions.

CONCLUSIONS

Samples immersed in coffee and wine showed discoloration beyond clinically acceptable limits. After 30 days, discoloration occurred in all materials immersed in all solutions. At T3, VIS microhardness generally decreased, while TPF did not.

CLINICAL SIGNIFICANCE

After 30 days, all bulk-fill composites immersed in distilled water, coffee and wine showed clinically unacceptable ΔE₀₀ .

Effect of thione primers on adhesive bonding between an indirect composite material and Ag-Pd-Cu-Au alloy

The current study evaluated the effect of primers on the shear bond strength of an indirect composite material joined to a silverpalladium-copper-gold (Ag-Pd-Cu-Au) alloy (Castwell). Disk specimens were cast from the alloy and were air-abraded with alumina. Eight metal primers were applied to the alloy surface. A light-polymerized indirect composite material (Solidex) was bonded to the alloy. Shear bond strength was determined both before and after the application of thermocycling. Two groups primed with Metaltite (thione) and M. L. Primer (sulfide) showed the greatest post-thermocycling bond strength (8.8 and 6.5 MPa). The results of the X-ray photoelectron spectroscopic (XPS) analysis suggested that the thione monomer (MTU-6) in the Metaltite primer was strongly adsorbed onto the Ag-Pd-Cu-Au alloy surface even after repeated cleaning with acetone. The application of either the thione (MTU-6) or sulfide primer is effective for enhancing the bonding between a composite material and Ag-Pd-Cu-Au alloy.