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
How would you use Maxcem Elite (resin cement)?
Dual cure self adhesive
Automix
- Clean and dry tooth + restoration
- Select desired shade
- Bleed small amount onto mixing pad
- Dispense cement onto restoration or into root canal
- Seat restoration and hold with light pressure
- Remove excess after 2-3 minutes, or can use spot cure technqiue
- Light cure all surfaces for 10 seconds to set
*remove interpoximally with dental floss first as it sets hard
What are adhesive resin cements? How do they work?
-Adhesive monomers added to monomers to allow chemical bonding to suitably prepared metal surfaces
Monomers: MDP, 4-Meta
Monomers exhibit affintiy for base metal oxides in the alloy
- Low affinity for precious metals due to lack of oxide surfacee coating
- Resin can be bonded to precious metals by using alloy primer containing VBATDT (sulfur component facilitates bond to precious, semi-precious and base metals)
What are potential side effects of using Panavia F 2.0. (Kuraray) (dual cure resin cement)
Oral mucosa may turn whitish colour by ED primer II or alloy primer due to protein coagulation (temporary and lasts few days)
Cure inhibited by eugneol
_Haemostatic agents containing ferric may impair adhesion and cause discolouration around tooth margin
What is hte working time, setting time and steps for using Panavia?
Working time: 1 minute (40 seconds for post core)
Setting time: 3 minute
- Wash and dry tooth + restoration
- Etch tooth for 10 seconds with phosphoric acid
- Rinse and dry thoroughly
- Alloy Primer on metal restoration surface (if appropriate)
- Apply ED Primer II (to mix: dispense a drop of A and B, mix (doesn’t say how long for) and apply to tooth for 30 seconds and gently air dry)
- Dispense equal amounts of A and B cement paste, mix for 20 seconds and place onto internal surface of restoration
- Seat the restoration (cement cures and contacts with ED primer)
- Apply oxyguard II to restoration margin and remove after 3 minutes.
- Remove excess cement
What is the composition of zinc phosphate cements? (Note: this is a separate category to resin cements, not a subtype of resin cements; i.e. zinc phosphate is a different active ingredient to resins)
Powder: 90% zinc oxide
Liquid: 67% buffered phosphoric acid and small amount of aluminium
What are the properties of Zinc phosphate cements?
Affect on surrounding structures:
-Mechanical bonding
Durability/survivability
- High compressive strength
- Low tensile strength
- High elastic modulus (brittle and stiff)
- High solubility initially but falls rapidly as cement ages
- Reaches maximum physical properties within 24 hours of initial set
Benefits to patients:
-Low cost
Detriment to patinet
-Low pH (pH 4 after one hour of delivery–>post op sensitivity), but reaches neutrality by 48 hours
Handling/benefit to operators
- Not technique sensitive
- Low film thickness
What is the composition of Zinc polycarboxylate cements?
-Hybrid of zinc phosphate
Powder:
-Mostly zinc oxide and 10% magnesium oxide
Liquid: 30-43% high weight polyalkenoic acid
What are the properties of zinc polycarboxylate?
Durability/strength:
- Low modulus of elasticity (about 1/3 of zinc phosphate)
- Lower compressive strength than zinc phosphate (about 1/2 to 2/3)
- Good tensile strength (8-12 MPa, greater than zinc phosphate)
- More soluble than RMGIC’s and resin cements thus more prone to acid dissolution, however still reasonably resistant to water dissolution
Effect on other structures
-Some degree of chemical bond with tooth (free carboxyl groups react with calcium)
Benefits to patient
-Less pulpal sensitivity (rapid rise in pH after mixing, polyacrylic acid less acidic than phsphoric acid)
What is hte working time and setting time of Poly-F plus (zinc polycarboxylate cement)
- Work: 2 minutes
- Set 5-7 minutes
- Wash and dry tooth + restoration
- Mix 1 scoop of powder with 2 drops of distilled water with spatula on glass slab rapidly to creamy consistency (15 seconds)
- Apply to restoration, seat with gentle pressure
- Remove excess cement when set
Which cements have the greatest compressive and flexural strength out of Resin, Zn phosphate, GIC, RMGIC?
-Resin
Between self etch and total etch resins, which has the greater:
- Compressive strength
- Flexural strength
Comp: self etch
Flex: Total etch
What are the steps of cementing a crown?
- Inspect the crown
- Remove temp crown and cement
- Try in crown check fit, margins, aesthetics, occlusion + contacts, adjust if necessary, obtain patient’s consent
- Polish crown
- Cement and clean up
- Recheck occlusion
- Follow up appointment
What should you look for when inspecting the crown?
- Constructed as per lab instruction?
- Aesthetics: shade + anatomy
- Check the die: (wear, damaged spots, flaws)
- Fit, marginal adaptation, occlusion and proximal contact of crown on the die
- Air bubbles
What should be checked on the temp crown prior to cementation?
- Is temp crown intact/lost?
- Sensitivity
What are the consequences of a lost temp crown?
- Tooth sensitivity
- Bacterial ingress: pulpitis
- Adjacent tooth drift
- Over eruption of opposing tooth
- Damaged tooth prep
How much space is usually allowed for cements?
50 microns
When are air bubbles acceptable and unaccpetable?
If small on fitting surface will be filled with cement
However if margin unacceptable
What happens if there is a small marginal defect on gold and on ceramic crowns?
- On gold needs to be redone
- On ceramic can be added to margin
What instrument should be used to remove a temp crown?
-Small spoon excavator
What instruement should be used to remove remaining temp cement?
-Perio probe/explorer
What should be done when trying in veneers to help visualise aesthetics?
-Use try-in paste, otherwise steps are similar to crown try in
What are the steps to cementing a post?
- Shade selection for final crown
- Examine post for margins, defects, air bubbles
- Remove temp crown and temp cement
- Try in post and obtain patient consent
- Check occlusion and adjust if necessary (i.e. use putty key to check interocclusal space)
- Cement and clean up
- Crown prep + impression + temp crown
- lab instructions for final crown
What is the difference between luting and bonding?
Bonding= ahderence is achieved by chemical or micromechanical retention
Luting= no bond is formed, and retention achieved purely through physical friction holding restoration in
Cementation is a combination of the two
What are 5 factors to promote good adhesion?
- Clean adherend
- Good wetting
- Intimate adaptaion
- Bonding
- Good curing
What cements should be used for each situation?
Self etching resin or resin:
-Tooth coloured inlay, onlay and moderate strength all ceramic crowns
Resin cemetns:
- Ceramic veneers
- Crown or fixed prostheses that have come off repeatedly
- Tooth preparations with minimal or questionable retention
What should you check at the review appointement?
- Patient feedback re. sensitivity, discomfort especially when chewing, high bites
- Check crown re. margins, remnant cement, occlusion (if adjust polish afterwards)
- Schedule 6 month recalls
What are some potential errors that can go wrong with cementation?
- Broken core/prepared tooth
- Too tight contacts can not seat
- Too high occlusion
- Margins/occlusion become compromised after cementation despite being fine before
- Can not seat crown after loading cement (often need to retreat at this point)
- Sensitivity after cementation
- PBM crown debonded, chipped
- Veneer cracked, chipped
