What sits under what: the order of layers
Half of this vocabulary makes sense once you know the sequence from cavity floor to surface:
- etchant — usually phosphoric acid
- primer and bonding agent — the adhesive system, often one bottle in modern kits
- cavity liner — a thin layer, typically calcium hydroxide or glass ionomer
- cavity base — thicker and load-bearing
- the restorative itself — composite resin, amalgam, glass ionomer cement
Varnish is the older solution, sealing dentinal tubules. The liner/base distinction is about thickness and load-bearing capacity, not chemistry.
One word, cement, doing three different jobs
Cement does not imply a filling material by itself. A qualifier assigns its job:
- luting cement — for fixing a crown or inlay
- temporary cement and permanent cement — by intended duration
- glass ionomer cement — serves as both a restorative and a luting agent
- zinc phosphate, polycarboxylate, resin cement — named by chemistry
Adhesives follow the same logic: a total-etch adhesive needs a separate etching step, a self-etch adhesive etches as it primes. Bonding to ceramic adds a silane coupling agent.
Light-cured, self-cured or dual-cured
Three modes, printed on the packaging: light-cured (blue light), self-cured (chemical), dual-cured (both). Two parameters depend on the mode and are constantly confused:
- working time — how long you have to place and shape the material
- setting time — how long until it is fully set
Polymerization shrinkage is the reason composite goes in incrementally rather than in one bulk increment. Two properties are demanded of any material: biocompatibility and radiopacity — without the second it is invisible on a radiograph and indistinguishable from caries.
Impression, cast, and four grades of gypsum
The workflow runs impression material → cast. The materials:
- alginate — inexpensive, for study models
- polyvinyl siloxane and addition silicone — the same thing, two names
- polyether — accurate and rigid
- impression compound, bite registration material, tray adhesive — supporting cast
Then the gypsum family, ordered by hardness: dental plaster → dental stone → die stone. Casting adds investment material and separating medium.
Ceramics order by strength: feldspathic porcelain → lithium disilicate → zirconia. Alloys: gold alloy, cobalt-chromium alloy, nickel-chromium alloy, titanium, stainless steel.
Material names that mislead
- Impression is the negative, cast or model the positive — mould in dentistry refers to denture tooth shape, not the process
- Varnish here seals dentine; nothing to do with nail or wood varnish
- Stone is a gypsum grade, not a rock — die stone is the hardest
- Compound in impression compound means a thermoplastic material, not a chemical compound
- Primer rhymes with timer and is a bonding step, not an instruction manual
- Amalgam is always singular as a material; amalgams refers to separate restorations
