Restorative Materials In Relation to Paediatric Dentistry Flashcards
Name some of the restorative materials that are used for paediatrics
- Amalgam
- Composites
- GICs
- RMGICs
- Compomers
- Preformed stainless steel crowns
What needs to be considered when choosing a restorative material for a child patient
- Clinical situation - National guidelines
- Tooth structure and cavity depth
- Longevity
- Toxicity
- Patient/child compliance - procedure length and moisture control
- Parents consent
What is the required retentive cavity depth for dental amalgams
2mm.
What are the benefits of choosing dental amalgams
- Good longevity
- Cost effective, economical, easy to use
- Excellent mechanical properties
- No shrinkage
- Not moisture sensitive (delayed expansion due to Zn presence)
What are the disadvantages of using composites
- Cured in 2mm increments
- Shrinkage/contraction on polymerisation
- Not natively adhered needs etching/bonding agent
What are the benefits of using composite filling materials
- Good creep resistance and compressive strength
- Excellent aesthetics
- Command set - light
What are some of the limitations of composites
- Adhesive first and then retenion
- Greater polymerisation shirnkage in large restorations
- Dentine bonding is weaker than bonding to an acid-etched enamel
- High wear in contact areas
- Thermal expansion coefficient (TEC) mismatch
- For posterior restorations permanent/primary have to be considered - wear resistance, water absorption, polymerisation shrinkage
- Not a complete polymerisation
- Potential leaching of toxic monomer (bisphenol A)
What causes GICs to release ions like Ca2+ and Al3+
When the glass reacts with polyacrylic acid it degrades and releases these
What is the reaction medium for the acid base reaction to make GICs
Water
What kind of bond do GICs make with enamel and dentin
Chemical - carboxyl groups bind to calcium in the tooth apatite
What are some benefits of using GICs
- Fluoride release
- No shrinkage, no exotherm
- Not toxic
- Ease of placement in bulk
- Ultra conservative restoration
- Aesthetic
What are the limitations of using GICs
- Low strength and high wear at early stages
- Need protection from dehydration
- Low Diametral tensile strength
- Low tensile strength - brittle
- Not able to withstand high tensile loads
- Restoration to be supported by tooth tissue
What setting reactions are involved in Resin-modified GICs
- Acid-base reaction = Glass + Polyacid
- Light-activated free radical polymerisation of methacrylate groups of the polymer (HEMA)
What are the advantages of RMGICs over GICs
- Command set
- Tougher
- Earyl strength
- Improved longevity
- Can set in the dark
What is a disadvantage of RMGICs
HEMA is cytotoxic
What filler is used in Compomers (PAMCs)
Ionomer glass
How are Compomers (PAMCs) set
Entirely by light
What are the advantages of compomers (PAMCs)
- Fluoride release
- Longevity
- Greater strength than GIC and RMGIC
What are the limitations of Compomers (PAMCs)
- Polymerisation shrinkage
- Exothermic reaction
- Bonding has to be done
What are PMCs/SSCs and where are the most often used
PMC = preformed metal crown
SSC = Stainless steel crowns
Extracoronal restoration for primary teeth.
What makes steel become stainless steel
The addition of chromium and nickel to the Iron and Carbon of steel
Why is stainless steel corrosion resistant
the chromium forms Cr2O3 at the surface
What proportion of chromium is in stainless steel
> 11%
What are the 3 types of stainless steel
Ferritic
Austentic
Martensiticc
What is the composition of austenitic type stainless steel
Cr - 16-22%
Ni - 7-22%
C - 0.2%
What are some of the benefits of stainless steel crowns
- Strong - tensile strength
- Durable
- Preventative
- Cost effective in long term
- Available in pre-fabricated sizes
How are stainless steel crowns cemented to the tooth surface
Using luting cements like GICs, Zinc polycarboxylate and zinc phosphate
What is the additional advantage of of using GICs and zinc polycarboxylate luting cements for SSCs
These will bond to the oxide layer on the stainless steel and the tooth so better adhesion
What are the limitations of PMCs/SSCs
- Aesthetics
- Complex procedure
- Nickel/Chromium allergy/sensitivity
- Veneer crown - composite resin used on top for aesthetics
- Tooth coloured prefabricated
Name some preventative materials
- Toothpaste, mouthwash
- Topical fluoride - varnishes, gels, tablets
- Sealants
What does replacing the hydroxyl in apatite for fluoride do to its properties
- More acidic resistant
- Chemical strengthening of enamel
- Reduce plaque activity - inhibits bacterial adhesion
Describe fluoride gels and how they work
- High viscosity water solution
- Thixotropic - viscosity decreases on pressure
- Flows around the surface and sticks to the teeth
What sources of fluoride are used in fluoride gels
- Sodium Fluoride - NaF
- Stannous Fluoride SnF2 -(pH~2)
- Acidualted phosphate fluoride (APF) (pH-3) - deeper fluoride penetration
What conc of fluoride source is there in fluoride gels
1-2%
What gives fluoride the thixotropic property
The soluble cellulose base polymer
What is the composition of Acidulated phosphate fluoride
- Sodium fluoride - 2%
- Hydrogen Fluoride - 0.34%
- Orthophosphoric acid - 0.98%
- Hydroxyalkyl cellulose - thickening
What are pits and fissure sealants used for and on
- Primary and permanent teeth
- Reducing dental caries
- Fluoride release therapy
- Clear, opaque or coloured forms
What can the pits and fissure sealants be based on
- Resin based
- GIC based
- Resin modified GIC
- Compomer
What are the main properties of pits and fissure sealants
- High coefficient of penetration
- High surface tension
- Low viscosity
- Good wetting
What do fluoride varnishes contain as a fluoride source
5% NaF - 2.26% - 22,600 ppm
1% difluorsilane - 1000ppm
What do fluoride varnishes contain besides the fluoride sources
Natural resin that is dissolved in an organic solvent
How do fluoride varnishes work
Solvent evaporates or sets in mouth
- Thin film covers tooth surface
- CaF2 like deposit is believed to convert into FAP
- Bitter taste and tooth discolouration
How long do fluoride varnishes release for after application
Hours lol
What bases can Resin sealants have
BisGMA
UDMA
Cyanocrylate
What is added to BisGMA resin sealants to reduce the viscosity
MMA monomers or TEGDMA
Describe the structure of Bis-GMA
Diglycidil ether of Bisphenol A with methacrylic acid
How can resin sealant be cured
Light
Self cured or chemically
How are light cured resin sealants cured
Diketone-amine activation
How are self/chemically cured resin sealants cured
Peroxide-amine activation
What issues need to be considered with resin sealants
- Depth of cure
- Oxygen inhibition layer - source of unpolymerised monomer
- Acid etch of enamel
What are resin sealants filled with and what advantages do these have
Filled with SiO2 or glass to improve wear resistance and radiopacity
What initiates polymerisation in cyanoacrylate
Water
How viscous are cyanoacrylate based resin sealants and what does this mean for its properties
Very low so have a good penetration and are able to bond to the protein matrix of enamel and dentin
What are some limitations of cyanoacrylate resin sealants
- Prone to hydrolysis
- Low tensile strength and abrasion resistance
- Toxicity - therefore not used
Compare GIC sealants to Resin Sealants
Note: Low viscosity GIC used
- GIC sealants have great fluoride release
- GIC = chemical adhesion
- GIC = more viscous so less penetration
- GIC = lower retention, more brittle
- Less resistant to occlusal wear
How do RMGIC sealants compare to GIC and resin sealants
Better retention and wear than GICs
But lower than resin-based
