Restorative Cements Flashcards
What are the 4 basic classes of cements?
- Phosphate
- Phenolate
- Polycarboxylate (zinc Polycarboxylate, Glass Ionomer)
- Resin
Setting time is
Time from beginning of mixing of cement, to hard and ridgid state in mouth.
Working Time is
Time available for clinical manipulation
Phenolate cement types (primary types)
- Calcium hydroxide
2. Zinc Oxide Eugenol (ZOE)
Organic compound in ZOE
Eugenol
Water and elevated heat ______ZOE reaction
Accelerate
Zinc Eugenolate is ______________ by moisture
Easily hydrolyzed
Free Eugenol
- Remains within and diffused out of set material.
2. Acts as potential anti-inflammatory
Obtundent means
Reduces irritation or has a soothing effect on a tissue.
Eugenol is derived from
Clove oil
What agents accelerate the setting of ZOE cements?
- Water
- Zinc
- Salts (acetate & sulfate)
- Acidic materials
Why do ZOE cements have high solubility?
- Hydrolytic breakdown of zinc eugenolate
2. Extraction of eugenol from set cement
What materials can be added to ZOE cements to improve their strengths?
- Mineral Fillers
- Silica or alumina
- Natural resins (ex. pine rosin)
- Synthetic polymers (ex. Polymethyl methacrylate)
- Polystyrene
- Polycarbonate
What effect does ZOE have on resin restorations?
Inhibits polymerization of resin (results in softening and discoloration)
IRM is a type of ZOE cement that
- Used as temp. Restorative material
- Contains 10-40% resin polymer in powder to strengthen cement
- Compressive strengths of 35-55 mPa
Calcium hydroxide 2 paste system is
- Base paste (Salicylate)
2. Catalyst paste (calcium hydroxide, barium sulfate, acryl toulene sulfonamide)
Organic component of Calcium hydroxide is
Acryl toulene sulfonamide
Calcium hydroxide cement achieve radiopacity b/c of which component
Barium Sulfate
Calcium hydroxide cross-linking occurs in the presence of ______
Water
Calcium hydroxide liner’s primary intended use
Vital pulp therapy
Application of calcium hydroxide on direct opening (exposure)
Direct Pulp capping (DPC)
Application of calcium hydroxide on a very thin area of remaining dentin is called
Indirect pulp capping
Why is calcium hydroxide a good pulpal floor liner
- Kills remaining bacteria
- Stimulates formation of reparative dentin
- Pulp tissue healing
Calcium hydroxide cement (not liner) is also called
DYCAL
Why should Calcium hydroxide cement be covered by a layer of resin modified glass ionomer
DYCAL (calcium hydroxide cement) has low compressive strength (12mPa) so RMGI will increase compressive strength.
Calcium hydroxide chelate cements are based on what specific setting reaction?
Salicylate esters
Calcium hydroxide and zinc oxide (small constituent) form chelate with salicylate esters
What new calcium hydroxide formulas are intended to overcome low physical properties and potential solubility issues (original CaO chelate cement issues)
Polymerizable resin compositions containing calcium hydroxide (alternative to replace use of CaO)
CaO chelate STILL MOST COMMON FORM SOLD (original formula)
What factors affect setting rxn of Polycarboxylate cements?
- Powder/liquid ratio
- Reactivity
- Particle size (of Zinc-oxide)
- Presence of additives
- Molecular weight and conc. Of poly acrylic acid
Give possible reasons for the minimal effect of Polycarboxylate cements on pulp?
- Relatively high pH of setting cement
- Localization of polyacrylic acid molecules.
- Minimal osmotic effect in dentin tubules
Describe powder composition of a conventional glass ionomer cement
Ground and milled alumino-silicate glass
Two forms:
- Calcium aluminum fluorosilicate glass
- Strontium aluminum fluorosilicate glass
Describe liquid component of conventional glass ionomer cement
50% polyacrylic-isotonic acid and tartaric acid (5%)
Mix w/ powder. Leach calcium and aluminum ions to surface. Cross link to form gel which then hardens.
Tartaric acid: Increase handling, increase working time, increase strength
Glass Ionomer are what type of composites
Tru “molecular” composite
Aluminum-silicate glass become chemically bound to poly salt matrix via ionic bonds
Major advantages of Glass Ionomer
- High strength and stiffness
- Adhesion to tooth structure
- Translucency
- Leachable fluoride (cariostatic effect)
- Resistant to dissolution in mouth
What component in glass ionomer is responsible for tooth adhesion?
Carboxylic acid (on polyacrylic acid)
Major disadvantages of Glass Ionomer
- Initial slow setting
- Initial moisture sensitivity
- Variable adhesive characteristics
- Limited translucency
What material and technique improve resistance to dissolve in conventional glass ionomer cements?
Application of convention varnishes or polymerizable “surface sealers” (protect against premature moisture)
RMGI (resin-modified glass ionomer)
Hybrid ionomer : needs water in the matrix
Composition and setting reaction of RMGI cements (hybrid ionomer)
Acid-base rxn (normal) +free-radical, addition polymerization (water soluble polymer and polymerizable monomers)
Use of co-polymers of acrylic acid and methacrylate monomers (dual-cure)
Advantages of light curing glass ionomer cements (RMGI)
- Dual-cure (acid-base & addition polymerization)
- High early strength
- Improved physical properties
- Water resistance
Primary curing mechanism for resin cements
Free-radical polymerization
Compomers differ from RMGI in the absence of which component
Water
Compomers have methacrylate-polyacid and glass, but not water
Formal name of compomer
Polyacid modified composite resin
Properties differences of RMGI and regular GI
- RGMI has early water resistance
2. Do not require varnish to protect against dissolution
What types of reactions that occur in setting of RMGI?
- Traditional glass-ionomer acid-base rxn
2. Free radical addition polymerization
How does temperature and humidity affect setting of ZOE and calcium hydroxide cements
Increased temp and humidity: DECREASE setting time
IRM has higher compressive strength than ZOE because of
Incorporation of polymethyl methacrylate (PMM) to powder
Foremost advantage of Polycarboxylate cements
- High biocompatibility
2. Low pulp irritation
Describe three possible curing modes for RMGI
- Light cure (free radical polymerization)
- Chemical cure (free radical polymerization)
- Acid- base rxn (poly acid liquid & silicate glass)
Luting cements ( 1 & 3 )
Liner-base (2 & 3 )
Conventional GI and Polycarboxylate cements share what composition components?
Liquid containing polyacrylic acid & water
Two materials produce high percentage of successful dentinal bridges with vital pulps
- Calcium hydroxide
2. Mineral trioxide aggregate (MTA)
Compomer composition
Polyacid-modified composite resin matrix consisting of
- Dimethylacrylate monomer (carboxyl groups)
- A filler of ion leachable glass (similar to GI filler)
NO WATER
Characteristics of Compomers
- Free radical polymerization
- Limited to no chemical bond to tooth structure
- Low fluoride release
- Delayed acid-base rxn (from water of tubules)
- Absorption
Advantages of Compomers
- Easy to place and polish
- Some fluoride release ( more than composite resins)
- More aesthetic than glass ionomer
- Better mechanical properties than GI
Disadvantages of Compomers
- Inferior mechanical properties than composite resin
- Less fluoride than GI
- Minimal fluoride discharge
- Little to no chemical bond with tooth
Giomer composition
Glass ionomer partial that is pre-reacted.
Free radical polymerization similar to light-activated resin composites
No chemical bond to tooth (needs bonding agent)
Outer shell releases fluoride