Modeler liquids: Effect on the cohesive strength, color and staining resistance of stratified resin composite restorations.

Purpose: To evaluate the effect of filled and unfilled modeler liquids on the cohesive strength and color stability when applied in between the resin composite layers in the stratification technique and on the uppermost surface layer.

Methods: For the cohesive strength test (n= 10), 30 cylindrical samples were packed into a Teflon mold (6x2 mm) in 2 mm increments. Firstly, a dentin-shade resin composite (Empress Direct) was placed, followed by the accommodation of a body-shade resin composite (Filtek Z350 XT) and an enamel-shade resin composite (Estelite Omega). Before photoactivation of each increment, an unfilled (Signum Liquid) or filled (Modeling Resin) modeler liquid was applied between the first and second layers and on the uppermost surface layer. The control group (n= 10) did not receive modeler liquid. Cohesive strength was measured in a universal testing machine. For the color test (n= 10), the other 30 samples were fabricated for the cohesive strength test, except for the difference in the diameter (6x6 mm). Before and after the staining of the samples, color was measured using the CIEL*a*b* system with a spectrophotometer (EasyShade). Data were submitted to ANOVA, Kruskal-Wallis test, or Mann-Whitney test (α= 5%).

Results: Modeler liquids significantly increased cohesive strength (P= 0.008), while ΔEab (P= 0.003) and ΔE₀₀ (P= 0.005) values presented significantly lower changes for the groups that received modeler liquids, with no significant difference between unfilled and filled modeler liquids.

Clinical significance: Apart from increasing the interfacial strength of stratified restorations, modeler liquids minimized staining.