The problem: too many syringes, and the wrong one in the cavity
A restorative drawer fills up fast: a universal composite in eight shades, two flowables, a bulk-fill someone tried once, a core material, and a syringe of something bought for a single case. The clinical questions are simpler than the drawer suggests. Which class of composite for a deep Class II? For a cervical lesion? For a core under a crown? For a child's molar? This guide answers by cavity type, explains what each class is designed to do, and points to the stocked products for each.
Understand: what separates the classes
Filler and handling
Composites are resin plus glass or ceramic filler. Higher filler loading means a stiffer, more wear-resistant, lower-shrinkage material that is packable; lower loading means a flowable material that adapts to the cavity floor but shrinks more and wears faster. Nano-hybrid and nano-filled universal composites sit in the middle: sculptable, polishable and strong enough for occlusal surfaces.
Depth of cure
Light reaches only so far into a composite. Conventional materials are placed in increments of about 2 mm because that is the depth a curing light cures reliably. Bulk-fill composites are formulated, through translucency and photoinitiator chemistry, to cure to 4 mm or more in one increment, which is the definition of the class. That depth is claimed for the manufacturer's stated light intensity and time, so the curing light matters as much as the material.
Shrinkage stress
All composites shrink when they cure. The stress that shrinkage puts on the bond depends on the cavity shape and on how much bonded surface each increment has. Bulk-fill materials use stress-relieving chemistry or lower elastic modulus to keep that stress acceptable in a single deep increment; flowables have the highest shrinkage of all and are kept thin.
What the evidence says about bulk-fill
- Evidence. A systematic review and meta-analysis of clinical trials in posterior permanent teeth found bulk-fill composites had survival and clinical performance comparable to conventional composites.1
- Evidence. A second systematic review comparing bulk-fill and incremental placement, with follow-ups from six months to ten years, found no significant difference in failure rates, marginal adaptation, discolouration or post-operative sensitivity.2
- Practice. Bulk-fill saves chair time in deep posterior cavities; the capping layer of a conventional composite is still recommended by most manufacturers for flowable bulk-fills and gives the better polish.
Options: the composite classes we stock
| Class | What it is for | Stocked examples |
|---|
| Universal nano-hybrid | Anterior and posterior restorations of every class; the everyday material | 3M Filtek Z250, Dentsply Neo Spectra ST (HV and LV), GC G-ænial A'CHORD, HanFil Universal |
| Bulk-fill, flowable and packable | Deep posterior boxes and cores in one 4 mm increment, usually capped | Dentsply SDR Plus, 3M Filtek Bulk Fill Flowable |
| Flowable | Liners, small Class I and V cavities, repairs, sealing undercuts | HanFil Flowable, Prime-Dent Flowable kit, GC everX Flow (fibre-reinforced flowable) |
| Fibre-reinforced | Dentine replacement in large posterior cavities and cusp replacement, under a capping layer | GC everX Posterior, GC everX Flow |
| Core build-up | Cores under crowns, often dual-cure for depth where light cannot reach | CharmCore Dual-Cured, Build-It FR, Fusion Core DC Flo |
Compare: by cavity type
| Cavity | Recommended class | Increment and cure (manufacturer figures) | Stocked pick |
|---|
| Class I or II, moderate depth | Universal nano-hybrid | 2 mm increments, cure per shade and product, typically 10 to 20 s | Filtek Z250 or Neo Spectra ST |
| Class II, deep box (over 4 mm) | Bulk-fill base plus universal cap | One 4 mm increment of bulk-fill, then a 2 mm cap | SDR Plus with Neo Spectra ST cap |
| Large cavity with lost cusp or thin walls | Fibre-reinforced base plus universal cap | Up to 4 mm of fibre-reinforced composite, then 1 to 2 mm cap | everX Posterior with Filtek Z250 cap |
| Class III or IV anterior | Universal nano-hybrid, layered enamel and dentine shades | Thin layers; polish with a dedicated kit | G-ænial A'CHORD layering kit |
| Class V cervical, non-carious | Flowable or low-viscosity universal | One or two thin increments | HanFil Flowable or Neo Spectra ST LV |
| Core under a crown | Dual-cure core material | Bulk placement; self-cure reaches where light cannot | CharmCore Dual-Cured A3 |
| Primary molar | Universal or bulk-fill, or glass ionomer in high caries risk | As above; see the glass ionomer comparison | SDR Plus or a glass ionomer |
Choose a universal nano-hybrid as the one syringe the clinic cannot do without. Add a bulk-fill if deep posterior boxes are a regular part of your day. Add a flowable for liners and small cavities, and a fibre-reinforced composite only if you routinely rebuild large posterior teeth.
Recommended products
Universal composites, the everyday syringes:
Buying advice
A three-syringe standard covers most practices: one universal nano-hybrid in the four or five shades you actually use, one bulk-fill, one flowable. Buy the adhesive from the same manufacturer where you can, and check that your curing light delivers the irradiance the bulk-fill's instructions assume. The finishing kit is part of the system: a well-chosen composite polished badly looks worse than a modest one polished well.
