Cements Flashcards
What types of permanent/definitive cements are there? What categories are they divided into?
Contemporary
- GIC
- RMGIC
- Resins
- Adhesive resin
Traditional
- Zinc phosphate
- Zinc polycarboxylate
What types of temporary/provisional cements are tehre?
Zinc oxide eugenol
Zinc oxide non eugenol
Resin
What are the ideal properties of cements?
Patient benefits
- Biocompatible
- Anticariogenic
- Shade options
- Strength, high wear resistance, low setting stress
- Good marginal seal
- Aesthetic/colour stability
Operator benefits
- Sufficient working time
- Low film thickness
- Radiopacity
- Ease of use
Durability:
- Low solubility
- Good comp;ressive + tensile strength
- Adhere to tooth structure and restorative materials
What are the methods of action of cement?
Mechanical + micromechanical
-Physical interlocking with surface irregularities
Chemical bonding
-Adhesive chemical bond can sometimes be formed between tooth and cement or cement and restoration
How can micromechanical retention be enhanced? What sort of restorations is this most effective on?
-Surface roughening via:
-Air abrasion
-Acid etching
Most effective on restorations with high tensile strength such as resin and RMGIC
What brands of GIC cement are available in clinic?
- Ketac Cem
- Fuji I
What brands of RMGIC cement are available in clinic?
Fuji Plus
Fuji Cem
What resin cements are available in clinic? What are their cure and bonding properties?
*Self adhesive=self etch
- MaxCem Elite
- Dual cure
- Self adhesive
- Rely X Unicem II
- Dual cure
- Self adhesive
- Nexus III
- Dual and light cure
- Total etch
- Panavia F 2.0
- Dual cure
- Adhesive resin (monomer contains component that bonds to precious and semi precious metals)
What Zinc polycarboxylate cements are available in clinic?
-Poly F plus
What Zinc phosphate cements are there (note not available in clinic)
- Fleck’s
- Hy-Bond
What are the components of GIC cements?
Powder:
- Calcium aluminosilicate glass
- Fluoride powder (controls cement formation and modifies physical properties)
Liquid:
- Dilute polyalkenoic acid (e.g. polyacrylic acid)
- Maleic acid
- Itaconic acid
What are some properties of GIC?
Handling:
- Sensitive to early moisture contamination and dessication
- Water absorption can cause degradation of cement, loss of translucency, decreased cement hardness
- Dessication can cause crazes and cracks if left for more than 10minutes–>cohesive failure
- Low film thickness + constant viscosity after mixing–> good seating
- Working time 2 - 3.5 minutes
Durability
- Low modulus of elasticity
- High compressive strength
- Poor wear resistance
- Use in caution in areas of high occlusal load
Effect on structures:
- Has chemical adhesion to tooth structure due to chelation with calcium and phosphate ions in dentine and enamel
- Slow, long term fluoride release–>cariostatic
Aesthetics
-Good translucency
For Ketac Cem, what are:
- Working time
- Setting time
- Steps in using
Above what temperature is setting time accelerated
Work time: 3 minutes
Setting time: 7 minutes
Steps:
- Clean and dry tooth and restoration
- Condition cavity for 20 seconds, rinse and gently air dry, avoid further saliva contamination
- Depress Aplicap, place in activator and activate once
- Mix in high frequency mixer Capmix (10 seconds) or Rotomix (8 seconds)
- Apply thin coat of cement to internal surface of restoration
- Seat restoration with firm pressure
- Remove excess after set
- Setting time accelerated above 23 degrees
- Longer mixing times=shorter working times and vice versa
What are RMGIC cements composed of?
- Hydrophilic monomers or polymerisable resin added to conventional GIC
- Also contains polymerisation inhibitors and moderators
- Hence setting reaction both acid base as in GIC and chemical/light initiated of resin
- Also include other di-methacrylates such as ethylene glycol methacrylate and glycidol methacrylate
- Also contains Bis-GMA
What are the properties of RMGIC cements?
Handling:
- Less moisture sensitive vs GIC
- Susceptible to dehydration shrinkage for up to several months post insertion–> cracks at exposed tooth cement restoration interface
- Film thickness similar to GIC (low)
Dimensional stability:
- Curing shrinkage (due to resin component)
- Volumetric expansion (over long term due to hydrophilic nature of added resin causing water sorption)–>unsuitable for veneers, all ceramic crowns, posts ( as ceramic weak to tensile forces which expansion applies)
Durability/longevity
- Higher compressive and tensile strength vs. GIC but lower vs resins
- Less soluble vs GIC
- However, concerns over long term stability
Effect on structures
- Some fluoride release
- Adhesion to tooth structure similar to GIC
What is the working and setitng time of Fuji Plus GC? (RMGIC) What are the steps in using it?
Working time: 2.5 minutes
Setting time: 4 minutes (autocure)
- Clean and dry tooth + restoration
- Condition tooth with 10% polyacrylic acid for 20 seconds
- Rinse and gently dry tooth and restoration, avoid saliva contamination
- Place capsule in activator and depress once, mix in rotational mixing device for 8 seconds
- Apply to internal restoration surface
- Seat on tooth within 30 seconds
- Remove excess after 1 minute while at gel stage
- Maintain isolation until set
What is the working and setting time for Fuji Cem GC? (RMGIC). What are the steps for usage?
Working time 2 minutes
Setting time 4.5 minutes (autocure)
- Clean and dry tooth + restoration
- Condition tooth for 20 seconds with 10% polyacrylic acid
- Rinse + gently air dry
- Dispense and mix Fuji Cem RMGIC in mixer for 10 seconds (it is hand mixed)
- Apply to internal restoration surface and seat within 30 seconds
- Remove excess after 1.5 minutes
What are resin cements composed of?
- Bis-GMA dimethacrylate or urethane demethacrylate based
- Fillers: 20 - 80% by weight (colloidal, silcat, barium glass)
What systems do resin cement come in?
- Powder/liquid
- Capsulated
- Paste/paste systems
What are the two ways of categorising resin cements? What are the types in each category?
Mechanism of cure:
- Self/auto
- Light cure
- Dual cure
Mechanism of bond:
- Total etch
- One step etch and bond (self-etch)
- Adhesive resin
What are the properties of resin cements?
Handling/operative factors:
- Variable film thickness
- Difficult removal (will require destruction of restoration generally, excess cement also difficult to remove
- Technique sensitive
- Eugenol inhbits polymerisation
- Light cure cements have higher colour stability and cure more completely after initial placement (vs dual or auto)
Patient benefits/disadvantages
- Good aesthetic qualities
- Post-op sensitivity (especially with total etch or deep preparations
Durability/longevity:
- Good compressive and tensile strength (equal to or greater than other cements)
- Low modulus of esasticity
- Low solubility
Effect on surfaces:
- Micromechanical bonding to tooth
- Chemcial bonding to etched and silanated porcelain
- Have dentine bonding ability
- Suitable for post and post-core restorations
Dimensional stability:
-Polymerisation shrinkage
How long does it take for chemical cure resin cement to mature/reach full bond strength?
- 24 hours
* Patients should be advised to avoid loading restoration for first hour after cementation
What is the working and setting time of relyX Unicem 2 cement (resin cement)? What are the steps to using it?
Dual cure, self adhesive
Working time: 2 minutes
Setting time: 5 minutes
- Wash and dry tooth and restoration
- Place capsule in activater and depress holding for 2-4 seconds
- Mix in mixer for 10 seconds
- Apply to internal surface of restoration and seat
- Spot cure margins for 2 seconds or wait 2 minutes for partial self cure and remove excess
- Light cure for 20 seconds each surface (40 seconds for fibre posts)
*use elongation tip for posts and take at least 5 seconds with immersion technique
What are the steps for using Nexus III (resin cement)?
- Dual core total etch
- Comes in automix form and multiple sahdes
1.Use try-in gel to select appropriate cement colour
2. Wash off try-in gel and dry restoration and tooth
3. Prepare restoration for bonding (e.g. if porcelain etch with hydrofluoric acid and apply silane agent)
4. Etch tooth for 15 seconds, wash and dry
5. Apply primer, gently air dry and apply adhesive. Light cure 20 seconds
6. Dispense cement onto internal restoration surface and seat
7 spot cure for 2 seconds and removve excess
8. Light cure for 40 seconds for complete cure