cementation Flashcards
What is the classification of cements?
Liners and bases
Temporary cements
Permanent cements
What are liners and bases?
GIC eg. Fuji IX
RMGIC eg. Fuji II
Bulk fill, C factor reduction
Command set w light cure
Can etch for strong bond w dentine bonding agents
Can adhere to unetched hard tissue
Exhibit sustained fluoride release
What are temporary cements?
Between prep and definitive
Can be a week to several months (usually 2 weeks)
Can be used to assess pulpal health, gingival healing, implant integration, aesthetics and functional change evaluation
What can loss or failure of the temp lead to?
Pain
Over eruption and loss of space
Drifting of proximal teeth
Damage to core prep
What are the functions of temporary cement?
Provide a seal
Prevent marginal leakage
Prevent pulpal irritation
Low strength for easy removal
Protect prep
What are the ideal properties of temp cement?
Seal against leakage of oral fluids
Low solubility
Biocompatible
Chem compatibility w polymer
Ease of use/removal
Easy to eliminate excess
Adequate working/setting time
Compatible w definitive luting agent
What materials are used for temp cement?
Fine particle ZOE (Tempbond- Kerr)
Non Euganol (Tempbond NE- Kerr)
Also, Zinc phosphate, zinc polycarboxylate and GIC
But, these are too high strength so difficult removal and prep damage
What are the advantages of ZOE?
Easy removal/use
Acceptable sealing properties
Obtundent effect on pulp
What are disadvantages of ZOE?
Eugenol+resin=bad combo
Eugenol acts as plasticiser of methacrylate and reduces surface hardness and strength
Can interfere w bond strength of cements
Inhibits polymerisation of certain composites
Must ensure all cement removed before definitive
What is the ideal permanent cement?
Adequate working time with rapid set
Low film thickness
Low solubility
High compressive and tensile strengths
Low viscosity
Adhesive
Biocompatible
Cariostatic
Translucent/opaque
Radiopaque
What are some historical permanent cements?
Zinc phosphate
Zinc polycarboxylate
Conventional GIC
Zinc oxide cements
What permanent cements are used?
RMGIC
Total etch adhesive resin cements (self cure, light cure, dual cure)
Self etching resin cements
What is RMGIC?
Hybrid of resin and GI components
Insoluble
Bonds to inorganic phase of dentine
Adheres to tooth structure/ceramic (not strong)
Used for metal-based
Contraindicated for ceramic due to hygroscopic expansion (leads to fracture)
Eg. Rely X luting
How does RMGIC work?
Contains
Acid soluble glass
Polyacid polymers (polyacrylic/itaconic/maleic)
Polymerising dimethacrylates
Polyacid polymers react w calcium in glass filler and dentine
Dimethacrylates polymerise into solid resin
Combines GI and resin tech
What is the composition and setting of RMGIC?
Powder (ion-leachable glass)
Liquid (methacrylate resin- bisGMA)
Acid-base and polymerisation reactions
HEMA allows resin and acid components to coexist in aqueous solution + take part in polymerisation
Water allows ionisation of acid component for acid-base reaction
Polymerisation activators and stabilisers
What are the advantages of RMGIC?
Adequate strength
Easy manipulation/use
Low film thickness
Fluoride release
Minimal post op sensitivity
Some adhesion to enamel and dentine
Resistance to moisture and marginal leakage
What are the disadvantages of RMGIC?
Dehydration shrinkage due to GI component
Can occur after 3 months
Can create stress fracture and cement-tooth interface
HEMA- increased water sorption, so plasticity and hygroscopic expansion
Cement bulk v hard and difficult to remove
What are total etch adhesive resin cements?
TOOTH
1. Pretreatment w 37% phosphoric acid
2. Dentine bonding agent application
CERAMIC
1. Etch w hydrofluoric acid for micromechanical retention
Resin cement + silane applied to crown
Only used w silica containing materials which etch w HF so not alumina or zirconia cores
Isolation is v essential
What are total etch adhesive resin cements composed of?
Resin matrix of bisGMA or urethane dimethacrylate and filler of fine inorganic particles (20-80%) for thin film thickness
What are the advantages of total etch adhesive resin cements?
Superior compressive and tensile strengths (20-50MPa)
Insoluble
Adhesive
Micromechanical bonding
Wide range of shades/translucencies
What are the disadvantages of total etch adhesive resin cements?
Highly tech sensitive (reacts v badly w moisture)
High film thickness
Marginal leakage (p. shrinkage)
Severe pulp reactions w cut vital dentine
No fluoride release
Low modulus of elasticity
Difficult to remove excess hardened
Why is a silane coupling agent needed?
Allows 2 materials to bond together
What is a self cure resin cement?
Chemical reaction of 2 materials, don’t react to light
Useful when light doesn’t penetrate
Mostly used for Maryland wings, metal inlays/onlays, endo posts, thick restorations
Eg. Panavia 21
What is a light cure resin cement?
Photoinitiators- need to be completely activated or can fail
Depth of at least 1.5mm
Lots of shade options- try in pastes
Eg. Calibra
What is a dual cure resin cement?
Can cure w or w/o light
Enough self cure initiators w addition of light to help process and seal margins
Can be used for ANY metal free restoration
Eg. Panavia F 2.0
What are self etching resin cements?
Don’t need etch or pre treatment
Comes in capsulated form
Can cement metallics, ceramic, PFMs BUT it’s important to remember that the prep and crown are perfect and you’re not relying on the cement
Eg. Rely X Unicem
What is the bonding strength like for self etching resin cements?
Low bond strength
Bonding between resin cement + zirconia core is difficult due to chemical inertness and lack of silica content (can’t etch)
What are the ideal cements for different materials?
Metal/metal or PFMs= Rely X luting (RMGIC)
High strength ceramic substructure- zirconia, alumina= Rely X Unicem
Glass-ceramic= Calibra (+ HF, silane primer, bonding agent)
