Zest Bulk EZ PLUS Bulk Fill Composite Refill, 6 g Syringe with 6 Tips · A2/B2

• Universal composites — The general-purpose paste, thicker than a flowable because it carries more filler. Light-cured composite of this kind is placed in layers of about 2 mm.
• Flowable composites — Thinner, because it carries less filler: it flows and adapts to the cavity more easily, but is more open to wear and shrinks more on curing than denser composites. The ADA describes flowables as typically used as a liner or base, or in low-stress areas.
• Bulk-fill composites — Placed in one layer of about 4 mm instead of several 2 mm layers. It comes as a thin base material that is covered with a conventional composite, or as a full-body paste that needs no covering.
• Composite kits — Several shades or viscosities of one line in a single box, in place of one syringe.

Packable composites, made with coarse or high-fraction filler so they can be condensed in back teeth, sit at the other end of the same scale from flowables. There is no separate packable shelf here.

Filler and viscosity: viscosity rises with filler loading, and more filler is what improves resistance to wear.

Layer depth: bulk-fill products have been marketed with increment depths from 4 to 10 mm. The depth that actually cures also depends on the light, the exposure time, the shade and the translucency.

Strength class: ISO 4049 sets a minimum flexural strength of 80 MPa for materials the maker claims for chewing surfaces and 50 MPa for all others.

Radiopacity: under ISO 4049 a flowable composite should be at least as radiopaque as the same thickness of aluminium, and a systematic review reported that a number of flowables on the market were not.

Shade: studies found that a flowable and the universal composite of the same line differ in colour, translucency and fluorescence, so the same shade name is not a guaranteed match.