Rheological properties of flowable resin composites and pit and fissure sealants.

OBJECTIVES: The purpose of this research was to determine the viscoelastic properties of commercially available flowable resin composites and resin-based pit and fissure sealants. The weight percentage of filler particles and the morphology of the filler particles were also investigated. METHODS: Eight flowable resin composites (Admira Flow, Filtek Flow, FlowLine, Grandio Flow, Point-4 Flowable, Revolution Formula 2, Tetric Flow and X-Flow) and four pit and fissure sealants (Clinpro, Delton FS(+), Estiseal F and Guardian Seal) were tested. Rheological measurements were performed using a dynamic oscillation rheometer. The filler weight content was determined by thermogravimetric analysis (TGA) and the morphology of the particles was investigated by scanning-electron microscopy (SEM). RESULTS: Flowable resin composites are non-Newtonian, shear-thinning materials. As the shear rate increased, the complex viscosity decreased drastically. They all showed elasticity even at the lowest frequencies. They also all showed thixotropy. Pit and fissure sealants are non-Newtonian, very low-viscosity fluids. No correlation was found between the rheological properties and the filler weight content or the particles' shape. SIGNIFICANCE: Huge differences are observed in the viscosity and flow characteristics of flowable resin composites that can have a potential influence on their clinical behavior during handling and thus on their clinical indications. Pit and fissure sealants show very different rheological properties from one another.