Dental Materials Flashcards
Constituents in composite ?
Filler particles, resin, camphorquinoine, low weight dimethacrylates, silicane coupling agent.
Purpose of filler particles in composite ?
Influence mechanical properties and aesthetics.
e.g. Quartz or Silicane glass.
Purpose of resin in composite ?
Allows for free radical polymerisation.
e.g. BisGMA.
Purpose of camphoquinoine in composite ?
Photo initiator in free radical polymerisation.
Purpose of silicane coupling agent in composite ?
Bonds the glass filler particles and resin.
Purpose of low weight dimethacrylates in composite ?
Alters the viscosity of the material.
Constituents of calcium hydroxide ?
Base - calcium hydroxide and zinc oxide.
Catalyst - butylene glycol disalicylate.
Constituents of zinc oxide eugenol ?
Base - zinc oxide.
Acid - eugenol.
Constituents of resin-modified zinc oxide eugenol ?
Base - zinc oxide.
Acid - eugenol.
Contains PMMA resin.
Constituents of EBA ZOE ?
Base - zinc oxide.
Acid - eugenol.
Contains quartz and alumina filler particles and ethobenzoic acid.
Advantages of EBA ZOE ?
Contains filler particles, encouraging crystalline structure so has greater mechanical properties compared with conventional EBA and resin-modified.
Constituents of conventional GIC ?
Base - silica, alumina, CaF and aluminium F.
Acid - poly acrylic acid and tartaric acid.
Can also contain lithium and silica to increase opacity and make radiopaque.
Constituents of RMGIC ?
Base - fluoro-alumino-silicate glass and potassium persulphate.
Acid - HEMA resin, polyacrylic acid with pendant methacrylate groups.
Purpose of potassium persulphate in RMGIC ?
REDOX catalyst in resin cure in the dark.
Purpose of methacrylate groups in RMGIC ?
Polymerisation reaction.
Clinical uses for composite ?
Large cavities extending into dentine with large occlusal bearing load.
Where aesthetics are important.
Inlays and onlays.
Labial veneers.
Clinical uses for CaOH ?
Direct and indirect pulp capping where small pulpal exposure for <24 hours.
Use RMGIC over the top - poor mechanical properties.
Clinical uses for ZOE ?
Lining material in deep cavities.
Temporary restorations.
Periodontal dressings.
Root canal sealer.
Clinical uses for conventional glass ionomer ?
Fissure sealants.
Restorative material on non-load bearing teeth i.e. cervical or root caries.
Cavity lining material.
Endo access cavity temporary restoration.
RMGIC should be used under all amalgam and large composite restorations.
What is the acid etch technique ?
- 35% phosphoric acid to etch the surface - 20 seconds for enamel and 10 seconds for dentine.
- Low viscosity BisGMA or dentine bonding agent and light cure 20 seconds.
- Use higher viscosity composite resin filling material for definitive restoration.
For acid etch technique, enamel must be …
Dry or it will prevent the flow of resin into the roughened surface.
How does acid etch technique i.e. total etch work ?
- Dentine - removes the smear layer.
- Enamel - roughens the surface (characteristic keyhole structure).
- Decalcifies the outermost layer, exposing dentinal tubules.
Allows for micromechanical interlocking of resin with enamel surface by penetrating the tubules and molecular entanglement = formation of hybrid layer.
Results in increased surface energy by also removing contaminants and greater wettability.
Why is bonding to dentine difficult ?
- Non-inert inorganic wet material with collagen and H2O.
- Dentinal tubules continually release dentinal fluid, prevents flow of resin.
- Inconsistent structure - denser tubules near pulp and more calcified near ACJ.
- Low surface energy and smear layer.
Ideal properties of dentine bonding agent ?
Ability to flow so low viscosity.
Adhesion to substrate (via combination of forces).
Potential for intimate contact with dentine.
