Dental Cements Flashcards
What can dental cement materials be used for in dentistry?
- To help the restoration to attach to the teeth e.g. luting, fixation, cementation i.e. luting inlay crowns, bridges, veneers on the prepared tooth
- It can help reduce/eliminate micro leakage (CaOH/ZnO)
- It improves the seal at this interface and reduces the need for replacement restorations
- Protects the pulp from heat (thermal insulation) and from chemical irritation (liners and bases) - to stimulate secondary dentin formation (CaOH, bioactive liners)
- Temporary filling material (RMGI), aesthetic restoration (GI), ortho brackets, root canal sealers
What is a luting agent?
A material that acts as an adhesive to hold together indirect restorations to the tooth structure. Luting agents are designed to be either permanent or temporary.
What are permanent luting cements used for?
For long-term cementation of cast restorations such as inlays, crowns, bridges, laminate veneers and orthodontic fixed appliances.
What are temporary luting cements used for?
Temporary/provisional cements are used when the restoration will have to be removed. Most commonly, temporary cement is selected for the placement of provisional coverage.
What variables affect cements?
- Mixing time
- Humidity: if the clinical area is humid, premature exposure of the cement to these environments can create a loss of water from the liquid of an addition of moisture to the powder
- Powder: liquid ratio - incorporating too much/too little powder will alter the consistency. Thicker mixes set faster.
- Temperature
- Thickness: thin enough to fill the space, not too thick as this can cause occlusal problems
Traditional cements
- Powder/liquid formulations
- Powders are basic/amphoteric (proton acceptors)
- Liquids are acidic (proton donors)
- Setting reaction is that of acid-base leading to formation of a salt
What are the ideal properties of dental cements?
- Physical properties: good flow characteristics with low viscosity and film thickness, low solubility (not dissolved in water resulting in a gap)
- Translucency
- Radiopacity
- Biocompatibility (dental pulp and soft tissue)
- Mechanical properties: high compressive and tensile/shear strength
- Handling properties: adequate working time and ease of use (mixing/clean up)
Types of dental cements
- Adhesive (chemical and mechanical interlocking): resin based
- Non-adhesive (conventional): filling space- luting agent, Micromechanical only (Water based)
Zinc Oxide + Phosphoric acid =
Zinc phosphate
Zinc oxide + Polyacrylic acid =
Zinc polycarboxylate
Polyacrylic acid + fluorosilicate glass =
GIC
Phosphoric acid + fluorosilicate glass =
Silicate
Zinc oxide eugenol
- Zinc oxide reacts with eugenol (oil of cloves) to form a chelated structure
- Powder: zinc oxide + zinc acetate (1-5%)
- Liquid: eugenol + olive oil (5-15%)
- Sets very slowly unless moist (4-10 mins, 12 hours to complete)
- The reaction is sensitive to water
- Mechanically weak, high film thickness
- Contaminate and soften acrylic resins
- Can be used as a lining in deep cavities without causing harm to the pulp
- Desensitising effect on dentine - oil of cloves
- Main uses: dressings, temporary cementation
- Trade names: RelyX Temp E (3M), Sedanol (Densply)
Resin bonded ZnE
- Powder: zinc oxide
- Liquid: eugenol + resins
- Very low irritancy to pulp, stronger than ZOE
- Main uses: linings
- Trade name: Kalzinol (Densply)
EBA Cement
- Powder: zinc oxide + zinc acetate + resin + silica
- Liquid: eugenol + resin + EBA
- Stronger than ZOE, as EBA helps to produce a stronger matrix to hold the particles together
- Main uses: temporary fillings, temporary cementation
- Trade name: Stailine (Staident, UK), SuperEBA
Zinc Phosphate
- Powder: zinc oxide + 10% magnesium oxide + trace Bi2O3 + BaO
- Liquid: phosphoric acid + water + aluminium phosphate
- Very fast reaction that results in the formation of zinc phosphate, mixing time 1.5-2mins and setting time 2.5-8mins
- When the powder is mixed with the liquid, the phosphoric acid attacks the surface of the particles and releases zinc ions into the liquid
- Water is critical to the reaction
- Reduced P/L ratio: liquid degradation (clouding of the liquid), loss of water from acid (the liquid should not be dispensed until mixing is to be initiated water evaporation)
- A cool glass slab should be used for mixing to prolong setting times. The liquid should not be dispensed until mixing is to be initiated because water will be evaporated.
Type 1: used for luting casting, permanent restoration. Smaller particles that enable the cement to flow out into thin (<25um) layers between a casting and a tooth.
Type 2: all other applications. Contains larger particles and achieve a film thickness of 40um.
Main uses: luting agent, temporary restoration
Trade names: De Trey Zinc (Densply Sirona)
Copper Cement
- Powder: zinc oxide + black copper oxide
- Liquid: phosphoric acid
- Black appearance and bactericidal effects due to copper
- Main uses: fillings in deciduous teeth, cementing splints and orthodontic devices (limited use nowadays)
Silicate cements
- Powder: powdered glass containing alumina + silica + fluorides
- Liquid: phosphoric acid
- They were the 1st directly placed aesthetic filling materials
- They are too acidic, irritating pulp, brittle and highly soluble so they are rarely used nowadays
Silicophosphate cements
- Powder: mixture of ZnO + aluminosilicate glass
- Liquid: phosphoric acid + buffers
- A hybrid of silicate and phosphate cements
- Main uses: fillings in children’s teeth, cementing porcelain crowns and orthodonic bands
- Trade name: Petralit, Kryptex
Polycarboxylate cement
- Powder: zinc oxide (+10% magnesium oxide)
- Liquid: polyacrylic acid solution (conc 32-42 wt%)
- Formation of zinc polycarboxylate
- Rapid setting reaction 30-40s. it is pseudoplastic hence care should be taken not to produce thinner mixes.
- 1st cement exhibiting chemical bond to tooth structure.
- Trade names: Hy-bond (Shofu), Durelon (3M), PolyF plus (Dentsply Sirona)
- Immediate strength between that of ZnO eugenol (Weak) and Zn phosphate (Strong)
- Reaches a neutral pH within 5-30 mins after mixing. GI takes slightly longer.
- ZnO/Eugenol has a neutral pH
- Mix P/L rapidly over 30 seconds, appears viscous but it flows under pressure, sets within 6-9 mins, soluble, adhesive and fairly biocompatible (pH rises to neutrality quickly)
Calcium Hydroxide
- Main constituent CaOh PASTE
- Simplest version a suspen
