Shear Bond Strength and Tooth-Composite Interaction With Self-Adhering Flowable Composites

Abstract

SUMMARY Purpose: To evaluate the tooth-composite interaction (A) and shear bond strength (SBS; B) of self-adhering flowables. Methods and Materials: (A) Thirty-two human molars with one Class V cavity were restored with Vertise Flow (VF), Fusio Liquid Dentin (FLD), an experimental self-adhering flowable (EF), or Adper Prompt-L-Pop/Filtek Supreme XT Flowable (PLP). Teeth were prepared according to laboratory standard and stored in water (24 hours, 37°C). Microleakage (ML; percentage interface length at enamel [E]/dentin [D]) and tooth-composite interaction were investigated. (B) The buccal surface of 160 embedded human molars was abraded to expose an enamel/dentin area of diameter ≥3 mm. Composite specimens were produced on enamel/dentin with VF, FLD, EF, or PLP. Prior to loading, 80 samples were water stored (24 hours, 37°C) and 80 thermocycled (5°C-55°C, 1500 cycles). The SBS was measured, and failure modes were classified by scanning electron microscopy. Statistics: Kruskal-Wallis, Mann-Whitney U, and Fisher exact tests were performed (α=0.05). Results: (A) At enamel margins, EF and VF showed significantly lower ML than did FLD and PLP (pi≤0.009; 81%-89%); in dentin, lower values resulted with FLD and VF compared with PLP and EF (pi≤0.01; 77%-94%). Adhesive tags at E were consistently verifiable with EF and VF but irregularly with FLD and PLP. At D, tags were detectable with all systems. (B) In all groups, SBS decreased by up to 97% after thermocycling. It was generally diminished with self-adhering flowables (E: 50%-98%, D: 59%-98%; pi<0.02). More cohesive defects were observed with PLP (pi<0.009). Conclusion: Tooth-composite morphology and bond strength indicate that the clinical use of self-adhering flowables must be pursued cautiously.