Lining And Base Cements Flashcards
What are the three functions of lining materials?
Therapeutic
Protective
Structural
What is a lining material?
Placed as an intermediary between dentine and restorative material
What are the therapeutic functions of lining materials?
Stimulate odontobalsst
Encourage remin
Bactericidal
What are the protective functions of linings?
Against thermal stimuli: metallic fillings readily transmit heat to underlying dentine
Chemical: some restorative materials are cytotoxic to pulp
Galvanic: this is thr flow of ions when dissimilar metals contact
What can micro leakage result in?
Sensitvity
Recurrent caries
Tooth discolouration
Why are the structural functions of linings?
Reduce the amount of filling material
Make the cavity shape less complex
Allows restoration with an inlay since blocks out undercuts and smooths walls
What are the ideal properties of a dents cement?
High early compressive strength Strong even in thin cross section Good pulp response Bactericidal Radiopque Not react with filling material Easy to mix Adequate working time Short setting time Seal odontoblasts tubules
What are the type of dental cements available?
Calcium hydroxide Zinc oxide eugenol Zinc phosphate Zinc polcarboxylate Polyalkenoates
How many pastes are there in CaOH paste 1 and paste 2?
Base: Paste 1: CaOH, ZnO, Zn stearate, ethyl toluene , sulfonamide
Catalyst: Paste 2: glycol salicylate, titanium dioxide, calcium sulfate, calcium tungstate
What are the advantages of CaOH?
Bactericidal to some groups of organisms
Stimulate relative dentine
Remin of altered dentine
What is in the Zn OxidenEugenol cements?
Powder: ZnO, Zn stearate and modifying agents: alumina, PMMA, polystyrene, polycarbonate
Liquid: eugenol (phenolic ether) and modifying agents: ethoxybenzoic acid
What are the properties of ZOE?
Bland
Phenolic ether provides bactericidal properties
Not compatible with composite as it plasticises Bis GMA
What are the cements bases on ZnO aluminium silicate glass?
Zn Phosohate
Zn Polycarboxylate
Silicate cements
Glass ionomer cements
What are zinc phosphate cements ?
Powder: Zn oxide and other metallic oxides
Liquid: buffered phosphoric acid and Zn and Al phosphate buffers
What happens on mixing Zn Phosphate is mixed?
Exothermic reaction so must be mixed on a glass slab
How is ZnPhosphate made?
The powder is made at 1000 degrees to reduce reactivity and MgO helps compressive strength
What is the purpose of buffers in the liquid of Zn phosphate cement?
To provide adequate working time
What is the pH of Zn phosphate cement at time of placement?
1.3 to 3.6
How long does it talks zinc phosphate to become neutral ?
24 hours
T/F Zn Phosohate cement has a low tensile strength ?
T but this means it is brittle
How soluble is Zn phosphate once it sets?
Low
What are zinc polcarboxylate cements made from?
Powder: Zn oxide And Mg O
Liquid: poly acrylic acid
What are the advantages of Polycarboxylate cements?
Antibacterial
Form weak bond to enamel and dentine
Bonds to stainless steel and tin plated restorations
What are the polyalkelonate cements made from?
GIC
Powder: sodium alumina silicate glass, calcium fluoride, pigments, freeze dried poly acid
Liquid: distilled water
What are the advantages of polyalkelonate cements?
Biocompatible
Fluoride effect
80% strength in one hour
Bonds to non Prescious metal alloys
What is the function of increasing the AL:Si ratio?
This makes the glass more reactive for weaker polyacids
What type of cavity liners are?
Varnishes
Bonding resins
Light curing glass ionomer cements
What are the components of cavity liners?
Solute: copal resin, shellac, zinc oxide, calcium OH
Solvent: ether, acetone, chloroform
What is the compressive strengths of the various lining and cements?
CaOH : 10Mpa by 90 seconds Zinc OxidenEugenol: 5-50Mpa Zinc phosphate: 140Mpa Zinc polcarboxylate 40Mpa Polyalkelonate: 130Mpa,m80% of strength within 1 hour and tensile of 12Mpa
