Flashcards
Year 2 Biomaterials 2
Cards in this deck (200)
- 1Define 'colour'The property possessed by an object of producing different sensations on the eye as a result of the way it reflects or emits light
- 2What is translucency?Translucency will depend on the ability of the light to travel through the material, where it will change due to absorption and scattering properties of the material and the background against which it is held
- 3Why is surface texture an optical property?Light can be reflected from a surface, as from a mirror, or scatted in all directions so texture plays an important role
- 4What colour system uses 3 attributes to describe colours?Munsell colour system
- 5Which 3 attributes are used to describe colours in the Munsell colour system?Hue
Value
Chroma - 6What do each of the following attributes of the Munsell colour system describe: 1) Value 2) Hue 3) Chroma?1 - how light or dark it is (lightness)
2 - basic colour
3 - intensity of the colour - 7Hue is the basic colour. What are the basic colours of each of the following shades: 1) A shades 2) B shades 3) C shades 4) D shades1) A shades = reddish-brown
2) B shades = reddish-yellow
3) C shades = grey
4) D shades = reddish-grey - 8Chroma is the intensity of the colour. If a colour has a higher degree of chroma, what does it have a higher concentration of?Hue
- 9Using the shade C3 as an example, what does the C represent and what does the 3 represent?C - hue (grey)
3 - value - 10What are some influencing factors when shade taking?Lighting conditions
Defective vision
Surroundings
Effect of contrasting colours
Shade guides - 11What are some extrinsic factors that affect the appearance of teeth?Staining (drinking, smoking, eating)
Tooth wear:
- Attrition (tooth-tooth contact, bruxism - drug use, stress)
- Abrasion (tooth-other objects)
- Erosion (chemical acid, bacteria, eating disorders) - 12What is the most common way of classifying polymers?Natural or synthetic
- 13Name some examples of natural polymers.Chitin/ chitosan
Alginate (from seaweed)
Collagen
Gelatin
Hyaluronic acid
Fibrinogen
Silk
Biopolymers - starch, proteins and peptides, DNA, RNA - 14What are the monomer units for each of the following biopolymers: 1) Starch 2) Proteins and peptides 3) DNA and RNA?1 - sugars
2 - amino acids
3 - nucleic acids - 15What is the main giveaway that a polymer is synthetic?It tends to start with poly-
- 16What are some examples of synthetic polymers?Polyethylene
Teflon polystyrene
Polyester
Polypropylene
Polymethyl methacrylate
Nylon
Silicone
Vulcanized rubber - 17What is a monomer?The smallest repeating unit in a polymer chain
- 18What are polymers?Long chain molecules consisting of many repeating monomer units
- 19What type polymer are acrylic denture bases made from?Polymethyl methacrylate
- 20What is the difference between a homopolymer, copolymer, and heteropolymer?Homopolymer - one fixed mer type repeated
Copolymer - polymer of two mer types
Heteropolymer - polymer of many different mer types - 21What do the structural characteristics of a polymer relate to?The material properties
- 22Name the 3 types of polymer structure and describe the properties of the material.Linear - uninterrupted straight chain (more viscous material)
Branched - occasional branches off longer chain (slightly more stiff)
Networked - many interconnected linear chains, one giant molecule (very stiff) - 23Name the two main methods of polymerisation.Addition
Condensation - 24What is addition polymerisation?A reaction between two molecules to produce a larger molecule without the elimination of a smaller molecule
Can be made of the same molecule (homopolymer) or different molecules (heteropolymer)
Results in no by-product
Carbon-carbon double bond (C=C) usually required - usually involves breaking this stable bond - 25What does not happen with addition polymerisation?There is no elimination of a smaller molecule (no by-product)
- 26What type of bond is usually required for addition polymerisation?Carbon-carbon double bond
(C=C)
(Usually broken in the process to produce a single bond to allow chain propagation) - 27What type of polymerisation produces polymethyl methacrylate?Addition polymerisation
- 28What type of polymerisation do resin composites usually undergo?Addition polymerisation
- 29How can addition polymerisation be activated?Heat
Chemical
Light - 30Describe the stages of monomers going through the process of addition polymerisation.1. Activation - produces free radicals/ unpaired electrons
2. Initiation - free radical reacts with monomer
3. Propagation - polymer chain elongates
4. Termination - free radicals reacts to form a stable molecule - 31What is the usual initiator in the addition polymerisation reaction of polymethyl methacrylate?Benzoyl peroxide
- 32What is condensation polymerisation?Occurs when a reaction between two molecules produces a larger molecule with the elimination of a smaller molecule
Reacting molecules are not usually the same
Results in a by-product such as water or alcohol
Carbon-carbon double bonds are not usually required - 33What is produced with condensation polymerisation?A by-product - e.g. water or alcohol
- 34What is not usually required for condensation polymerisation?Carbon-carbon double bond
- 35Which dental materials tend to undergo condensation polymerisation?Impression materials like silicones
- 36What is there an increase in when materials undergo polymerisation/curing?Molecular weight
- 37What is meant by the degree of polymerisation?The number of repeating units in a polymer
- 38What is molecular weight?The sum of the atomic weight values of the atoms in a molecule
- 39What is the total molecular weight of a polymer?The degree of polymerisation (number of repeating units) multiplied by the molecular weight of the repeating unit
- 40What does increasing molecular weight increase? What does increasing molecular weight decrease?Increases physical properties (higher strength, rigidity, viscosity)
Decreases processibility (e.g. higher temperatures needed to manufacture) - 41What was methyl methacrylate (MMA) replaced with for use in composite materials?Bis-GMA
(Bisphenol-A and glycidylmethacrylate) - 42Why was Bis-GMA invented as a replacement for MMA?Because it has a higher molecular weight (around 5 times) than MMA
Polymerisation shrinkage is therefore much lower (MMA = 22%, Bis-GMA = 7.5%) because the number of gaps needed to be closed is less - 43High molecular weight monomers make handling and processability of the material more difficult. Bis-GMA is quite bulky and more viscous because of this. What is usually done to improve this?Low-viscosity monomers, like MMA, EDMA, and TEGDMA are added to act as viscosity controllers
- 44How would you tend to describe the elastic modulus of polymers?Tends to be lower
- 45What are the advantages of polymers in terms of their mechanical properties?Greater post-yield deformability
Greater failure strain
Show viscoelastic behaviour (good handling) - 46How can the mechanical properties of polymers be modified?By:
- Blending
- Using copolymers
- Cross-linking
- Using plasticisers
- Modifying crystallinity
- Using fillers - 47What is meant by cross-linking of polymers? What will the degree of cross-linking dictate?Joining polymer chains joined by chemical bonds
Strength, toughness, modulus/viscosity, brittleness - 48What are plasticisers and what is their role?Low molecular weight molecules that essentially sit between the chains of a polymer
They hold the polymer chains further apart so the forces between them are reduced, which softens the material by lowering the Tg (glass transition temperature) - 49What dental material are plasticisers commonly used in?Acrylic soft lining materials
- 50What term describes the random fashion in which polymer chains usually twist, coil up and cross each other?Amorphous structure
- 51Polymer chains usually take on an amorphous structure but we can occasionally, by chance, get areas where the polymer chains line up parallel to each other. How would these regions be described?Crystalline
- 52What can be added to a material to strengthen it?Fillers
- 53What are fillers?Usually inorganic material resulting in a "composite" material, used to strengthen the material
- 54What types of fillers are there?Particulate (e.g. in a hybrid resin composite)
Fibre-reinforced (e.g. fibre-reinforced composite)
Structural (e.g. structural post for crown) - 55What can thermal energy do to polymers?Can break or untangle the polymer chains, resulting in random motion (Brownian motion) of chains and a liquid/melt state
- 56What is the glass transition temperature (Tg)?The temperature at which the material goes from a rigid, glass-like state to a more flexible, rubbery state.
- 57What are thermoplastics?Polymers that flow when heated (easily shaped with heat)
E.g. boil and bite mouthguards - 58What are thermosetting materials?Polymeric materials that cure through the addition of energy (usually heat, chemical, irradiation) to a stronger form
Usually liquid or malleable prior to curing, and designed to be moulded into their final form
Irreversible, cannot be melted and reshaped
E.g. PMMA, branched poleythylene - 59What are elastomers?Somewhere in between thermoplastics and thermosets
Long polymer chains that have some degree of cross linking and are rubbery (e.g. silicone)
Usually kept above the glass transition temperature
Can withstand high strains and elastic deformation - 60What causes a colour shift of dental polymers to yellow over time?The tertiary amine and benzoyl peroxide (initiator) darken over time
- 61Why are things like barium or zirconium often added to dental polymers?Because the polymers themselves are not radiopaque
- 62What will the degree of polymerisation give you an indication of in terms of the clinical use of the material?The depth of cure required
- 63What are the factors to consider when selecting composite materials?- Handling consistency
- Long-term wear
- Polymerisation shrinkage
- Shade selection choices
- Curing time
- Polish and polish retention
- Special needs like fluoride release
- Fluorescence
- Opalescence
- Mechanical properties - 64What is a dental ceramic?A compound of a metal and non-metal (e.g. oxides, nitrides, silicates) consisting of strong rigid ionic bonds
- 65When are dental ceramics often used?When the size of the preparation exceeds the limit of use of composites (veneers, inlays/onlays, crowns, bridges)
- 66Name some of the common dental ceramics.ZnO (zinc oxide)
SiO2 (silica)
ZrO2 (zirconia)
Porcelain (family of ceramic composed mainly of feldspar, quartz and kaolin fired at high temperature) - 67What is the main drawback of dental ceramics?Brittleness
- 68What are the main types of all-ceramic restoration classification?Material composition
Fabrication method
Fusing temperature - 69How can ceramics be classified according to material composition?Glass-based (amorphous)
Glass-infiltrated (Al, Mg, Zr)
Non-glass (crystalline) - 70How can ceramics be classified according to fabrication method?Castable ceramics (ceramic slurry)
Hot pressed ceramics (wax elimination)
Dry-pressing method (powder on oversized die)
Machined materials (CAD-CAM) - 71How can ceramics be classified according to fusing temperature?High - 1200-1400°C
Medium - 1050-1200°C
Low - 800-1050°C - 72What is adhesion?Attraction between two different contacting surfaces, promoted by the interfacial forces of attraction between them
- 73What is an adhesive?The substance that promotes adhesion of one substance or material to another
- 74What is the adhesive bond?The process of joining two materials by means of an adhesive agent that solidifies during the bonding process
- 75What two groups can adhesive materials be divided into?Direct:
GIC, RMGIC, polycarboxylate cement (e.g. PolyF), resin cement
Indirect:
Composite and compomer (using intermediate enamel/dentine bonding agents) - 76What are the main types of adhesion?Chemical adhesion
Mechanical adhesion
Combination of both - 77What is chemical adhesion dependent on?The chemical affinity of the adhesive material for the adherend surface
- 78What is mechanical adhesion dependent on?The engagement of the adhesive material in the undercuts that we create on the adherend surface (e.g. tooth surface)
- 79What are the benefits of adhesive materials?- Increased retention
- Conservative of tooth structure
- Reduction in secondary caries
- Reduction in microleakage
- Preventative-fissure sealant
- Reinforcement of weakened tooth structure
- Improved aesthetics - 801) What are some of the material factors affecting adhesion? 2) What are some of the patient related factors affecting adhesion?1:
- Surface wetting ability
- Clean and contaminant free surface
- Surface area/ roughness
- No air pockets between adhesive and surface
- Small dimensional changes
2:
- Good isolation
- Patient and site selection - 81What are dentine bonding agents?Materials which allow "bonding" between a composite and enamel/dentine
- 82What compound are all dentine bonding agents based on?All are methacrylate based
(Bis-GMA, HEMA) - 83Bonding to enamel is predictable and relatively easy due to its water content. What is the approximate water content of enamel?10%
- 84What is the acid etch technique?The process of cleaning and roughening a solid surface by exposing it to an acid and thoroughly rinsing the residue to promote micromechanical bonding of an adhesive to the surface
- 85Fill in the blanks: The acid etch technique is the process of cleaning and [1] a solid surface by exposing it to an [2] and thoroughly rinsing the reside to promote [3] bonding of an adhesive to the surface.1 - roughening
2 - acid
3 - micromechanical - 86What acid (and concentration) is usually used in the acid etch technique? What is the pH of the acid?30-40% phosphoric acid
pH 0.2 - 87How long does it take for decalcification to occur following application of pH 0.2 30-40% phosphoric acid etch?5-8 seconds
- 88What does acid etching do to the enamel rods?Decalcifies portions of the enamel rods - calcium salts are dissolved which exposes interprismatic and prism areas for interlocking tag formation with the bonding resin
- 89What type of bonding does the acid etch technique allow? What is it not?Purely mechanical bonding
It is not true adhesion - 90What is the bond strength of the acid etch technique?20 MPa
- 91What is Heliobond used for?Bonding to enamel only
(It is not a dentine bonding agent) - 92What is dentine bonding agent used for?Bonding to both enamel and dentine
- 93What percentage of dentine is composed of each of the following: 1) Minerals 2) Water 3) Organic material1) 50%
2) 25%
3) 25% - 94What makes bonding to dentine a bit more tricky in comparison to bonding to enamel?Dentine has a higher organic and water content (25% each), compared to enamel which only has a 2% organic and 10% water content
Dentine:
- Wet living tissue with proteinaceous exudate
- Protein matrix = low surface energy
- Dentine is hydrophilic (while composite is hydrophobic)
- Smear layer - 95What is the goal of bonding to dentine? What is therefore needed?To bond a hydrophobic, highly viscous composite to a hydrophilic adherend
Therefore, we need something to change the properties of the dentine surface or smear layer from hydrophilic to hydrophobic - 96What is the smear layer?The layer of debris produced on the surface when dentine is cut or prepared by dental instruments (also contains bacteria)
- 97What are the stages of bonding to dentine?1. Etchant (dentine conditioner)
2. Primer (coupling agent) - e.g. HEMA
3. Adhesive (sealer)
Note// These stages are often merged in bonding systems - 98What is the objective of etching dentine?To remove the smear layer and simultaneously demineralise the dentine surface to expose the collagen fibrils
- 99What two things do we want to happen when etching dentine?Removal of smear layer
Demineralise the dentine surface to expose collagen fibrils - 100What do we want to expose through etching dentine?Collagen fibrils
- 101How long do we etch enamel and dentine for?15 seconds for enamel
Then another 15 seconds etching enamel + dentine - 102Why is enamel etched for 30 seconds, while dentine is only etched for 15 seconds?Enamel is a much more mineralised tissue and requires a longer etching time to create the necessary surface irregularities for optimal bonding.
Over-etching dentine can damage its collagen fibres and weaken the bond - risk of collagen fibre collapse - 103What is a primer?A bi-functional coupling molecule dissolved in an organic solvent
It allows bonding of the hydrophobic adhesive resin/ composite to the moist hydrophilic collagen network
The organic solvent displaces the water allowing infiltration of the primer into the exposed collagen network - 104What do primers allow in dentine bonding?Bonding of the hydrophobic adhesive resin/ composite to the moist hydrophilic collagen network
- 105What are the couple molecules of primers dissolved in?Organic solvent
- 106What does the organic solvent of the primer do?Displaces the water which allows the primer to infiltrate into the exposed collagen network
- 107What are dentine bonding agents usually a mixture of?A hydrophobic monomer (e.g. Bis-GMA) and a hydrophilic monomer (e.g. HEMA) as the wetting agent
- 108Name some of the most commonly used tooth coloured restorative materials.Glass ionomer cements (GICs) - e.g. Fuji IX, Ketac-molar
Resin-modified glass ionomer cements (RMGICs) - e.g. Fuji II LC, Vitrebond
Composite resins - e.g. Filtek-supreme, Ceram-X duo
Compomers - e.g. Dyract - 109What type of tooth coloured restorative material is Fuji IX? What type of tooth coloured restorative material is Fuji II LC?Fuji IX - glass ionomer cement (GIC)
Fuji II LC - resin modified GIC - 110What group of tooth coloured restorative materials have had increasing popularity in recent years?Calcium silicate cements
- 111Give an example of a calcium silicate cement.Biodentine
Mineral trioxide aggregate (MTA) - 112What type of tooth coloured restorative materials are Biodentine and MTA?Calcium silicate cements
- 113Tooth coloured restorative materials can be categorised according to their setting reaction. What types of setting reactions might they have?Acid-base
Resin-polymerisation
A hybrid of the two
(Also, is there water involved in the setting reaction?) - 114Which tooth coloured restorative materials under go 100% acid-base reaction, water-base chemistry or have no resin involved?Conventional GICs
Calcium silicate cements - 115What is true about the setting reactions of conventional GICs and calcium silicate cements?100% acid-base reaction
or
Water-based chemistry
or
No resin involved - 116Which tooth coloured restorative materials undergo 100% resin-polymerisation or have resin-based chemistry or have no water involved?Composite resins
- 117What is true about the setting reactions of composite resins?100% resin-polymerisation
or
Resin-based chemistry
or
No water involved - 118Which tooth coloured restorative materials undergo mainly acid-base polymerisation, have mainly water-based chemistry, or have some resin involved?Resin-modified GICs
- 119What is true about the setting reaction of resin-modified GICs?Mainly acid-base polymerisation
or
Mainly water-based chemistry
or
Some resin involved - 120Which tooth coloured restorative materials undergo mainly resin-polymerisation, have mainly resin-based chemistry, or have some water involved?Compomers and Giomers
- 121What is true about the setting reactions of compomers and giomers?Mainly resin-polymerisation
or
Mainly resin-based chemistry
or
Some water involved - 122Rank the following tooth coloured restoratives from most to least amount of fluoride content/release/recharge: 1) Conventional GICs 2) Compomers and Giomers 3) Composite resin 4) Resin-modified GICs1, 4, 2, 3
- 123Rank the following tooth coloured restoratives from highest to lowest water content: 1) Conventional GICs 2) Compomers and Giomers 3) Composite resin 4) Resin-modified GICs1, 4, 2, 3
- 124Rank the following tooth coloured restoratives from most to least biologically active: 1) Conventional GICs 2) Compomers and Giomers 3) Composite resin 4) Resin-modified GICs1, 4, 2, 3
- 125As you go from 1 to 4 of the tooth coloured restoratives below, what is there an increase in? 1) Conventional GICs 2) Resin-modified GICs 3) Compomers and Giomers 4) Composite resinsIncrease in:
- Fluoride content/ release/ recharge
- Water content
- Biological activity - 126As you go from 1 to 4 of the tooth coloured restoratives below, what is there an increase in? 1) Composite resins 2) Compomers and Giomers 3) Resin-modified GICs 4) Conventional GICsIncrease in:
- Compressive strength
- Fracture toughness
- Bond strength
- Aesthetics - 127Rank the following tooth coloured restoratives from highest to lowest compressive strength: 1) Compomers and Giomers 2) Resin-modified GICs 3) Composite resins 4) Conventional GICs3, 1, 2, 4
- 128Rank the following tooth coloured restoratives from highest to lowest fracture toughness: 1) Compomers and Giomers 2) Resin-modified GICs 3) Composite resins 4) Conventional GICs3, 1, 2, 4
- 129Rank the following tooth coloured restoratives from highest to lowest bond strength: 1) Compomers and Giomers 2) Resin-modified GICs 3) Composite resins 4) Conventional GICs3, 1, 2, 4
- 130Rank the following tooth coloured restoratives from best to worst aesthetics: 1) Compomers and Giomers 2) Resin-modified GICs 3) Composite resins 4) Conventional GICs3, 1, 2, 4
- 131What 5 essential ingredients do modern conventional GICs contain?Acid
Base
Radiopaque filler
Reaction modifier/ complexing agent
Distilled water - 132Which acid do modern conventional GICs contain?Polyalkenoic acid polymer
- 133Which base do modern conventional GICs contain?(Ion-leachable) calcium-fluoro-alumino-silicate glass
- 134What property do fillers in modern conventional GICs have?They are radiopaque
- 135How are other types (non-conventional) of GIC created?By adding or substituting other ingredients (to the 5 essential ones)
E.g. RMGIC - polymerisable resin monomers, photoinitiator
E.g. Chemfil Rock (Zinc-reinforced GIC) - zinc additives - 136What are polyalkenoic acids? Name the 3 main polyalkenoic acids used to create glass ionomer cements.Family of acids that form complexes:
- Poly-acrylic acid
- Poly-itaconic acid
- Poly-maleic acid - 137What do the polyalkenoic acids form when left to stand?Polymer strands
- 138What type of polyalkenoic acid(s) is used to produce Fuji IX?Single polymer - polyacrylic acid only
- 139What type of polyalkenoic acid(s) is used to produce Ketac Molar?Copolymer - polyacrylic + polymaleic acid
- 140What type of polyalkenoic acid(s) is used to produce Chemfil Rock?Copolymer - polyacrylic + polyitaconic acid
- 141Which type of polyalkenoic acid is found in all GICs?Polyacrylic acid
- 142Which liquid component of GICs helps control the setting reaction and improve the working time?Tartaric acid
- 143How does tartaric acid work to control the setting reaction and improve the working time?Tartaric acid is a stronger acid than the polyalkenoic acids
This means it reacts first with the basic glass filler particles
Which delays the reaction of the polyalkenoic acids with the basic glass
So it stops the GIC setting too fast - 144Solids can be crystalline or amorphous. What is meant be each of these?Crystalline: atoms arranged in a regular order
Amorphous: atoms arranged in a random order - 145What type of structure does glass have?Amorphous
(It is produced when a solid, usually in crystalline form, is heated to extreme temperature and rapidly cooled) - 146What are the glass filler particles in GIC produced from?3 crystalline solids - silica, alumina, calcium fluoride
- 147Name the 3 crystalline solids that produce the glass filler particles in GIC.Calcium fluoride (CaF2)
Silica (SiO2) - majority component
Alumina (Al2O3) - 148Which crystalline solid forms the majority component of glass filler particles in GIC?Silica (SiO2)
- 149What does alumina provide to the GIC?The basic properties
- 150Which crystalline solid provides the basic properties to the GIC?Alumina (Al2O3)
- 151What does the calcium fluoride do to the glass filler particles in GIC?Make glass more susceptible to acid-attack
- 152How are the 3 crystalline solids (silica, alumina, calcium fluoride) turned into GIC glass filler particles?They are fused together at high temperature and cooled rapidly
- 153What is the name of the GIC filler particles produced by the heating and rapid cooling of the 3 crystalline solids?Calcium-fluoro-alumino-silicate glass
- 154Which ions are released in the GIC setting process?Calcium (Ca2+)
Fluoride (F-)
Aluminium ions (Al3+)
Silicate (SiO4 4-) - 155Complete the following chemical equation: Acid + Base = ?Salt + Water
- 156What is the general equation for any acid?H₂A
- 157What is the basic chemistry of the setting reaction of glass ionomer cements?Acid + Base = Salt + Water
- 158What is the chemical equation for the setting reaction of a GIC.
- 159What does silica form when it contacts with water?A gel
- 160What is the acid component of the acid-base setting reaction of GICs? What is the base component of the acid-base setting reaction of GICs?Acid: polyalkenoic acid
Base: calcium-fluoro-alumino-silicate glass - 161What salts are produced as a result of the acid-base reaction between polyalkenoic acid and calcium-fluoro-alumino-silicate glass in the setting reaction of GIC?Calcium salts
Aluminium salts - 162The setting time of glass ionomer cements varies according to the specific formulation. What is the typical setting time of GICs?1-3 minutes
- 163The GIC acid-base reaction occurs in 3 overlapping stages. Name these 3 stages.1. Dissolution
2. Gelation
3. Maturation - 164Why do the 3 stages of the GIC acid-base reaction overlap and occur at different rates?Because of the differences in the rate of release of the ions from the glass particles
- 165Order the following stages of the GIC acid-base reaction from first to last: 1) Gelation 2) Maturation 3) Dissolution3, 1, 2
- 166What happens in the dissolution stage of the GIC acid-base reaction?We have the polyalkenoic acid polymer
This dissociates in water and releases H+
It also forms polymer chains
The protons react with the outer layer of the glass particles and diffuse into the glass, which causes the outer layer to release ions (fluoride, calcium, aluminium)
Water combines with silica to form a gel on the outside of the glass particle
There is diffusion-based adhesion between the glass and polymer matrix - 167Which ion is released first and in the highest amount in the GIC acid-base reaction?Calcium ions (Ca2+)
- 168What happens in the gelation stage of the GIC acid-base reaction?Ca2+ plays a crucial role in the initial crosslinking (ionic) of the polyalkenoic acid polymers
Ca2+ can only bind 2 acid polymer chains together
Clinically, the GIC is becoming more gel like and is at its most vulnerable (must protect it from moisture and dehydration) - 169How many polyalkenoic acid polymer chains can calcium ions (Ca2+) bind together?2
- 170How does the GIC appear clinically when it is in the gelation stage of the acid-base reaction (usually within 1 minute of mixing)?Gel-like
- 171What happens in the maturation stage of the GIC acid-base reaction?Al3+ now plays a role in the hardening and maturation of the GIC
Al3+ can bond to 3 polymer chains at once
Takes 30 mins before any significant improvement in strength is observed (considered fully set in 24 hours) - 172Describe the final composition of a fully set GIC.Unreacted fluoro-alumino-silicate glass surrounded by a bonded silica gel embedded in a cross-linked polyalkenoate matrix
- 173During which phases of the acid-base reaction are GICs susceptible to hydration and dehydration (gain or loss of water)?Gelation and maturation phases
- 174What are the effects of early water contamination on GICs?Loss of Al3+ which are key to providing the overall strength of the GIC
Loss of polyalkenoic acid polymer chains
The GIC becomes more opaque - poor aesthetics are a sign of water uptake - 175What are the effects of dehydration (loss of water) on GICs?Cracking and fissure formation
Surface softening, crumbling
Chalky appearance - 176Once a GIC restoration has been placed in the cavity and shaped, what might need to be done?It may need to be covered to protect it from hydration or dehydration
- 177Certain brands have their own specific coats for GIC restorations. What could these be?Resin-based - Bis-GMA
Acrylic-monomer based - methacrylate - 178What non-specific coating could be used to protect GIC restorations?Vaseline
- 179What are the methods of dispensing GICs?Hand-mixed and placed (manual):
- Powder + liquid (polyalkenoic acid)
- Powder + liquid (distilled water)
- Paste + paste
Pre-packaged and dispensed (automatic):
- Encapsulated
- Auto-mixing paste-paste - 180What is an extremely important characteristic about GICs?They chemically stick to teeth without any bonding agents
- 181How do GICs stick to teeth without the use of bonding agents?The main interaction occurs with the mineral (hydroxyapatite) found in enamel and dentine
The GIC "stickiness" develops during the dissolution/gelation stage - 182At what stage(s) of the acid-base reaction does the "stickiness" of GIC develop?Dissolution/gelation
- 183What 2 things are true about the adhesion/ bond of GIC to tooth?It is dynamic and matures with time
- 184Name the 4 stages of GIC adhesion to dentine and enamel.1. Wetting of the tooth surface
2. Micromechanical interlocking
3. True chemical bonding
4. Formation of the ion exchange layer - 185Order the following stages of GIC adhesion to dentine and enamel from first to last: 1) True chemical bonding 2) Formation of the ion exchange layer 3) Wetting of the tooth surface 4) Micromechanical interlocking3, 4, 1, 2
- 186Describe the following stage of GIC adhesion to dentine and enamel: Wetting of the tooth surfaceAs soon as you place the GIC on the tooth, it coats it very quickly
The components of GIC are all hydrophilic
Hydrogen bonds between the polyalkenoate polymers and the water in dentine - 187Describe the following stage of GIC adhesion to dentine and enamel: Micromechanical interlockingThe polyalkenoic acids etch the hydroxyapatite coated collagen fibril (this means the GIC is self-etching and acidic when first mixed)
Diffuses in between the collagen fibrils and interlocks - 188Describe the following stage of GIC adhesion to dentine and enamel: True chemical bondingIonic bonds form between the polyalkenoic acid and the calcium in the hydroxyapatite
- 189Describe the following stage of GIC adhesion to dentine and enamel: Formation of the ion exchange layerThere is substantial change in the interface between GIC and the dentine
Ions from the GIC and the tooth diffuse to the GIC-tooth interface, including calcium and fluoride ions - 190Do we need to condition or etch the tooth surface before placing a GIC?It depends on the manufacturer:
Fuji IX requires 10s of 10% polyacrylic acid (GC Cavity Conditioner)
Ketac-Molar requires 30s of 25% polyacrylic acid (Ketac Conditioner)
Chemfil Rock does not require any conditioning of dentine - 191GICs are self-adhesive. What component found in enamel and dentine do they form ionic bonds with?Ca2+ in hydroxyapatite
- 192When might glass ionomer cements be used clinically as temporary restorations?Class I and II posterior cavities
Endodontic access cavities (if there is a large gap between appointments - 193When might glass ionomer cements be used clinically as permanent restorations?Class III and V cavities
All deciduous cavity types (I-V) - 194What are some of the clinical applications/uses of glass ionomer cements?Temporary restoration (class I and II posterior cavities, endodontic access cavities)
Permanent restoration (class III and V, deciduous)
As a base under a restoration (composite or amalgam)
Fissure sealant
Core build up material (depending on brand) - 195What are the contraindications for the use of glass ionomer cements?Direct pulp cap
Indirect pulp cap
Patients with known allergy to any GIC component - 196Why are glass ionomer cements contraindicated for direct and indirect pulp caps?Because of the pH of the GIC when it is mixed - acidic initially so will irritate the pulp and cause reversible pulpitis
- 197What are some of the advantages of glass ionomer cements?Inherently adhesive and sticks to enamel and dentine
Therapeutic - fluoride-releasing
Cariostatic benefits
Good aesthetics
Easy to use
Can be placed in bulk
Biocompatible - 198What are some of the disadvantages of glass ionomer cements?Low fracture resistance
Susceptible to early water contamination of loss
Too sticky (difficulty handling, can stick to instruments) - 199There is a classification system for glass ionomer cements, ranging from Type 1 to 6. For types 1 to 4, give information on each of the following: - Intended clinical use - Commercial exampleType 1: luting/cementing
e.g. Aquacem
Type 2(.2): restorative purposes (reinforced type - posterior)
e.g. Fuji IX, Chemfil Rock
Type 3: liner or base under restoration
e.g. Fuji TRIAGE
Type 4: fissure sealant
e.g. Fuji TRIAGE - 200What do modern resin-modified GICs consist of?Exactly the same as conventional GICs:
- Polyalkenoic acid polymer
- Alkaline/basic (ion-leachable) glass
- Radiopaque filler
- Reaction modifier/complexing agent
- Distilled water
Plus:
- Hydrophilic resin monomer (HEMA)
- Photoinitiator
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- Undergraduate Restorative Dentistry (Dental Materials) Flashcards on Year 2 Biomaterials 2, created by Riya X on 14/12/2024.
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- Riya X
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