Influence of the self-adhering strategy on microhardness, sorption, solubility, color stability, and cytotoxicity compared to bulk-fill and conventional resin composites.

Abstract

Objectives: To analyze and compare, in vitro, the microhardness, sorption, solubility, color stability, and cytotoxicity of three types of resin composites: self-adhesive (SARC) (Dyad Flow (DF)/Kerr), bulk-fill (Filtek Bulk Fill Flow (FBF)/3 M ESPE), and conventional (Filtek Z350XT Flow (Z350)/3 M ESPE).

Materials and methods: Thirty cylindrical specimens were prepared using a split metal mold (15 mm × 1 mm), divided into 3 groups (n = 10) according to the material used. Vickers hardness (VH) was calculated from three indentations (300gf/15 s) per specimen. The sorption and solubility were measured according to the ISO 4049:2009 specification after storing in distilled water for 7 days. The color of each resin composite was measured using a portable digital spectrophotometer according to the CIELAB system. After a 7-day immersion in coffee, the color variation (∆E) was calculated. Following the ISO 10993:2012, the cytotoxicity in Vero cells was evaluated through the MTT assay. The results were analyzed using the Kruskal-Wallis test to compare the studied groups. The Wilcoxon test was used to compare the assessments in each studied group. For cytotoxicity analysis, the data were compared by the ANOVA test (α = 0.05).

Results: DF showed the lowest VH (28.67), highest sorption (0.543 µg/mm³) and solubility (1.700 µg/mm³), and higher ∆E after 7 days of coffee immersion (p = 0.008). The resin composites studied were considered non-cytotoxic.

Conclusions: The SARC presented inferior mechanical and physical-chemical properties than bulk-fill and conventional resin composites, with comparable cytotoxicity against Vero cells.

Clinical relevance: The simplification of the clinical protocol of SARC can minimize the number of possible failures during the restorative technique. However, considering their inferior physical and mechanical properties, their coverage with materials of higher mechanical properties and physical-chemical stability should be considered.