Flow, strength, stiffness and radiopacity of flowable resin composites

This study was undertaken to characterize 9 currently available proprietary flowable composites with respect to key properties of flow, flexural strength, stiffness (modulus of elasticity) and radiopacity.

Seven proprietary flowable composites (Aelite Flo, Filtek Flow, Heliomolar Flow, PermaFlo, Revolution Formula 2, Tetric Flow, Wave) and 2 flowable compomers (Compoglass Flow, Dyract Flow) were evaluated. A universal hybrid composite (Filtek Z250) and a restorative compomer (Dyract AP) were used as controls. Standard mechanical testing of 25 x 2 x 2 mm bar specimens was carried out at 24 hours and 1 month. Flow testing used a fixed volume of material under consistent loading, and radiopacity was measured simultaneously for all materials using disk specimens of 1 mm thickness.

As expected, flowable composites showed higher flow and lower mechanical properties than the controls. Moduli of the composites were approximately 50% or less of the moduli of control materials, which indicates high flexibility. Flexural strengths approached that of the control composite. Flow properties varied widely. The material Tetric Flow had the highest radiopacity, above that of enamel and the control composite. Lowest radiopacity, below or equivalent to that of dentin, was shown by Wave and Revolution Formula 2.

The flowable materials possessed a wide range of mechanical and physical properties. Their lower mechanical properties suggest that they should not be used in bulk in areas of high occlusal loading. Within intracoronal restorations, clinicians are advised to use materials with high radiopacity. A wide range of fluidity options is available. The clinical applications and performance of these materials require further study.