Dr Fawzy GIC Flashcards
(151 cards)
1
Q
What is the composition of GIC?
A
Ion-leachable glass
Water soluble polyacids
Water
2
Q
What kind of reaction is the setting reaction of GIC?
A
An acid-base reaction
3
Q
How does GIC adhere to the tooth?
A
Ionic bonding
Micromechanical bonding
4
Q
What is the composition of RMGI?
A
Ion-leachable glass
Water soluble polyacids (may be methacrylate modified)
Methacrylate monomers
Water
Photoinitiators
5
Q
What kind of reaction is the setting reaction for RMG1?
A
Free radical polymerization
Acid-base reaction
6
Q
What kind of adhesion does RMG1 use to bond with tooth?
A
Ionic bonding
Micromechanical adhesion
7
Q
What is the compomer composed of?
A
Ion-leachable glass
Glass and silica fillers
Dimethacrylate monomers
Polyacid-modified methacrylate monomers
Photoinitiators
Silane coupling agents
8
Q
What does the compomer use for setting reaction?
A
Free radical polymerization
Acid-Base reaction (delayed)
9
Q
What is the type of adhesion that occurs with the tooth in the compomer?
A
Micromechanical with adhesive
10
Q
What is the resin-based composite composed of?
A
Glass and silica fillers
Dimethacrylate monomers
Photoinitiators
Silane coupling agents
11
Q
What type of setting reaction does the resin-based composite reaction use?
A
Free radical polymerization
12
Q
What type of adhesion does resin-based composite adhere to the tooth with?
A
Micromechanical with adhesive
13
Q
What are the biological requirements of restorative materials?
A
They must be:
Non-toxic
Cariostatic
14
Q
What are the physical requirements of restorative materials?
A
Should not erode or dissolve in saliva or fluid taken into the mouth
Good resistance to wear and fracture
Thermal properties similar to that of the tooth
Should adhere to tooth structure
Dimensional changes on setting should be low
Good polishability and retain a smooth finish
Radiopaque
Should have good and long term aesthetics
15
Q
What are the types of tooth coloured restorative materials?
A
Cements such as silicate cements and glass ionomer cements.
Dental resins such as acrylic (unfilled) resins and composite (filled) resins
Dental ceramics
16
Q
What kind of differences are seen between the types of direct tooth-coloured restorative materials?
A
A continuum exists between conventional glass ionomer and composite resins based on how much of the reaction is acid-base and how much is resin polymerization.
Conventional glass ionomer is more dependent on acid-base reaction and composite resins are more dependent on resin polymerization.
Continuum is as follows:
100% Acid-base reaction - Conventional Glass Ionomer -> Resin-modified Glass ionomer -> Compomer -> Composite resins - 100% Resin polymerization reaction
17
Q
What are silicate cements used for?
A
For class 3 and 5 restorations
18
Q
What are the limitations of using silicate cements?
A
Stains easily
Prevents secondary caries
Poor marginal adaptation leading to seepage and pulp death
19
Q
What is the composition of silicate cement powder?
A
Silica
Alumina
Sodium or calcium phosphate
Sodium or calcium fluoride
Arsenic
20
Q
What is the composition of silicate cement liquid?
A
42% phosphoric acid
10% Aluminum phosphate
8% Zinc phosphate
40% Water
21
Q
How does setting of silicate cement take place?
A
Hydrogen ions from the phosphoric acid attack the glass (outer surface) and displace the aluminum ions. Other ions are also displaced together with the fluoride ions
pH rises and the metal phosphates and fluorides precipitate to form the matrix which is mainly hydrated aluminum phosphate.
Surface of the powder particle remains as a hydrated alumino silicate gel due to replacement of the metal ion by hydrated protons.
22
Q
What is the final product of the setting of silicate cement?
A
Set cement is a composite material consisting of:
An inner core of unreacted positively charged particles.
A middle layer of siliceous gel bonded to the core by means of Si-O-Al bonds.
An outer layer of hydrated aluminum phosphate gel bonded to the siliceous gel by H-bonded molecules. (Water is essential for the formation of the cement, matrix forms 20 - 30% of the cement)
23
Q
What are the pros and cons of using silicate cements?
A
Cons:
Shrinks on hardening (Greater shrinkage occurs when it is allowed to dry out causing discoloration around the margins)
Dissolves and disintegrates in the oral fluids (Decreases with time and is accelerated by citrus fruits)
Weakest of all tooth-coloured restoratives (exception of unfilled resin)
Tends to discolour with time.
Has high acidity and an initial pH of 2.8 which increases to 5.8 after 28 days.
Pros:
Has good thermal properties
Has an anti-cariogenic effect attributed to fluoride release from the cement
24
Q
How does silicate cement carry out anti-cariogenic actions?
A
Fluoride reduces enamel acid solubility
Fluoride acts as an enzyme inhibitor to prevent carbohydrate metabolism by bacteria
Fluoride reduces the wettability of the enamel and thus makes plaque accumulation more difficult
Postulated that phosphoric acid present has initial inhibitory effect on bacterial growth for 24 to 48 hours
25
How is GIC different to Silicate Cements?
Silicate cement has phosphoric acid as an important component. Glass Ionomer Cement has Polyalkenoid acid.
GIC bonds to tooth structure but SC does not.
GIC causes minimal pulp irritation while SC is harmful to the pulp.
Fluoride in GIC is not involved in matrix formation while it is in SC.
Use of SC is more limited compared to GIC.
26
What are Glass Ionomer Cements composed of?
Derived from silicate and polycarboxylate cements. (ASPA I acronym)
Originally was designed as a replacement for silicate cements.
27
What chemical reaction does GIC rely on?
Acid-Base reaction between polyalkenoic acid and a calcium fluoro alumino silicate glass
28
What are the 3 main components of glass?
Silica
Alumina
Calcium fluoride
29
How is GIC made into the form that it is used as?
Mixture is fused at high temperature and the molten mass is shocked-cooled and finely ground to a powder before use.
Sodium, aluminum fluorides and calcium or aluminum phosphates are added to the mixture occasionally. (some materials contain strontium in place of calcium.
30
Why is strontium sometimes used instead of calcium?
Elements are interchangeable due to similar polarity and atomic size.
It is very dense meaning it makes the GIC more radiopaque.
Some potential anticariogenic effects
31
What are the clinical applications of GIC?
Based on type of glass ionomer:
Cementation of fixed prostheses
Restoration of primary teeth
Restoration of some permanent teeth: Class I and II ART, class II (tunnel restorations), Class III, Class V including non-carious cervical tooth loss.
Core build-up
Repair of defective restoration margins
Restoration of root surfaces for overdentures
Temporary restorations
Lining/base under composite and amalgam
Laminate restorations (sandwich technique)
Pit and fissure sealants
Bonding of orthodontic brackets
Bonding agent for composites
32
What contraindications should be considered for GIC?
Stress-bearing areas (large class II and IV cavities in permanent teeth and replacement of lost cusps)
Large aesthetic areas (Class IV cavities)
33
How is GIC supplied?
Powder and liquid
Powder and water (longer working time and half life)
Paste and paste
34
What is the composition of GIC powder/liquid material?
Powder consists of: Sodium aluminosilicate glass with 20% CaF and other minor additives
Liquid consists of: Aqueous solution of acrylic acid/itaconic acid polymer
Aqueous solution of maleic acid/acrylic acid copolymer
Aqueous solution of maleic acid copolymer
And tartaric acid in some products
35
What is the composition of GIC powder/water material?
Powder: Glass + vacuum-dried polyacid (acrylic, maleic or copolymers)
Liquid: Water with dilute aqueous solution of tartaric acid
36
What is the composition of GIC paste/paste material?
Paste A: Glass, HEMA (Hydroxyethyl methacrylate), dimethacrylate, catalyst
Paste B: Polyacrylic acid, distilled water, silica, and a catalyst
37
What is calcium fluoro alumino silicate glass similar to?
Glass is similar to that used in silicate cements with a higher ratio of alumina to silica.
38
What is itaconic acid important for?
Reduces the viscosity of the liquid which allows for easier mix and inhibits gelation caused by intermolecular hydrogen bonding.
39
What is tartaric acid important for?
Improves handling characteristics
Increases working time
Decreases setting time
40
How does setting take place in GIC?
Acid-base reaction: Complicated by presence of 2 markedly different cations in the glass (Ca and Al)
41
What are the 2 phases of setting of GIC?
Dissolution: Surface of glass is attacked by polyacid which results in limited dissolution of glass with release of calcium, aluminum and fluoride ions. Calcium is more readily released than aluminum ions through cement sol compared to calcium. Both calcium and aluminum will readily form complexes with fluoride ions. Aluminum fluoride is preferrentially formed over calcium fluoride.
Gelation: initial set is brought about by cross-linking of the COO- with more mobile and readily available calcium ions to form calcium polysalt. pH increases as polyacid is converted to polysalt. Over the next 24 hours, a maturation phase occurs during which aluminum salts are formed, leading to a more rigid cross-linking between the polyacid chain. Associated with progressive hydration of the matrix salts. This is responsible for the changes seen in the physical properties of the GIC.
42
What is set cement composed of?
Original glass particles sheathed by siliceous hydrogel and bonded by a matrix phase consisting of hydrated fluoridated calcium and aluminum polysalt.
43
What factors affect the rate of setting of GIC?
Glass composition: Alumina:silica ratio if higher that increases rate of set.
Lower particle size means more surface area which means theres an increase in rate of set.
Increased powder:liquid ratio means increase in rate of set.
Increasing mixing temperature increases rate of set.
Addition of tartaric acid increases rate of setting without shortening working time. Causes more rapid extraction of aluminum ions.
44
What is water balance like in GIC?
Glass Ionomer Cements are hydrolytically unstable during initial stages of setting reaction when calcium salts are being formed. They remain sensitive to water loss and uptake for at least 1 hour after mixing. Regular set cements.
45
What is the role of the water medium in GIC?
Reaction medium into which the cement-forming cations are leached and transported to react with the polyacid to form a polyacrylate matrix.
Serves to hydrate the cross-linked matrix thereby increasing material strength
46
How can water loss or gain affect the GIC?
Water loss: Dessication will retard the reaction and can cause shrinkage and crazing. Must therefore be protected by a suitable barrier (low viscosity resin is best)
Water gain: Exposure to moisture causes essential ions to potentially be eluted.
47
What happens if there is a disruption in water balance of GIC?
Both water loss and uptake in early stages of the setting reaction results in:
Reduction of physical properties
Compromised colour/translucency
48
How can GICs susceptibility to water balance be reduced?
Increase speed of setting reaction
Addition of light-activated resins
49
What are the features of the strength of GIC?
Has a high compressive strength and a low flexural strength.
1 year old cement is 2x that of 24hour old cement.
50
What factors affect the strength of GIC?
Strength decreases when dessication is allowed to occur.
Powder:liquid ratio affects the strength
51
What are the features of the solubility of GIC?
Values measured in water are slightly higher than other cements but not much and cements are very insoluble in oral environment.
Acid erosion values lower than other cements. GIC < Silicate < Zinc phosphate < Zinc polycarboxylate
52
How biocompatible is GIC?
It is very good at not irritating the pulp.
Polyacrylic acid is a weak acid and its diffusability is very low due to its large molecular weight. Acid is precipitated by calcium ions in the dentine and dissociation of hydrogen ions is limited.
53
Does the good biocompatibility of GIC mean it can be used directly on the pulp?
No, a calcium hydroxide sub-liner should still be used before placing GIC.
54
How does GIC respond to heat?
Low thermal diffusivity
Coefficient of thermal expansion is similar to that of the tooth. (Enamel = 11.4 (10^6/degrees C) conventional type2 GIC = 11 (10^6/degrees C))
55
How does GIC fluoride release affect the tooth?
Cement has a cariostatic effect due to fluoride release
It has the ability to release fluoride over extended periods of time as sodium fluoride and some as calcium fluoride. Sodium fluoride is not important for the matrix so it doesn't weaken the cement.
Set cement can absorb fluoride from oral environment and then release it slowly.
56
How aesthetic is GIC?
It has a problem of translucency.
Translucency improves with the maturity of the cement.
Early contamination of the cement with water affects translucency (It becomes more opaque)
Cement can be damagedby dehydration at subsequent visits (Protect previously placed restorations)
57
How good is adhesion of GIC to tooth structure?
It is very good and bonds to tooth structure. This allows for conservative approach to be taken for a restoration.
80% of maximum bond strength is developed in 15 minutes.
58
How does adhesion of GIC to tooth structure take place?
Mechanism hasn't been confirmed yet. But it is probably based upon diffusion and adsorption phenomena.
Bonding to hydroxyappatite (diffusion based adhesion)
Bonding to collagen
Adhesion is a true ionic exchange which requires the presence of water so it can be considered a dynamic bond.
59
How does GIC bond to hydroxyapatite?
Polyalkenoic chains penetrate the surface of hydroxyapatite, displacing and replacing surface phosphate.
Calcium ions are displaced equally with phosphate ions to maintain electrical neutrality
Displaced ions combine with the surface of the cement and form an intermediate layer of new material (ion-enriched / ion-exchange layer or interdiffusion zone) which is firmly attached to the tooth.
60
How does GIC bond to dentin?
Some degree of adhesion to collagen of dentin
This happens either through hydrogen bonding or metallic ion bridging between the carboxyl groups of the polyacid and the collagen molecules
61
What does GIC bind more strongly to enamel or dentine?
Enamel > Dentine
Resin-modified > Conventional > Metal-reinforced
62
Why are resin-modified and conventional composites more tightly bound than metal-reinforced structure to tooth structure?
Superior wetting ability of HEMA
Poorer flow properties of metal-reinforced materials
Possibly related to micromechanical bonding
63
What is adhesion dependent on?
Good adhesion is dependent on good wetting
For reliable bonding:
Surface should be smooth
Surface contaminants must be removed
Free polyalkenoic acid must be available to interact with enamel and dentin
64
How is the smear layer formed?
Created by rotary instrumentation during cavity preparation on enamel and dentin
65
What are the properties of the dentin smear layer?
Contains hydroxyapatite crystals and denatured collagen.
Generally 1 - 5 micrometers thick
Although partly porous, it dramatically reduces fluid flow from tubules
66
How can bonding to tooth structure be increased?
Pumice-water slurry
Surface conditioners
67
What do conditioners do?
They clean tooth surface (removing the smear layer)
Increasing surface energy
Allows cement to come into intimate contact with the tooth surface
68
What are the features of good conditioners?
Conditioning liquid should be able to remove smear layer without unduly demineralizing the surface of the tooth. (dentinal tubules remain partially blocked)
This is different to etching which is what is needed for resin attachment.
69
What concentration of polyacrylic acid is used for dentin conditioner?
10 to 25% aqueous solution of polyacrylic acid is generally accepted (10 to 20s) - originally 50% citric acid
70
What is the advantage of using polyacrylic acid for dentin conditioner?
Remaining residue will not interfere with setting reaction of cement
71
How is dentin conditioning for Resin-modified glass ionomers different?
It is possible to use other solutions instead of polyacrylic acid
72
How are composites adhered to enamel?
Selective removal of hydroxyapatite crystals by an acid (35 - 40% phosphoric acid) resulting in microporosities which are penetrated by hydrophobic monomers.
73
How are composites adhered to dentine?
3 ways:
Smear layer modifying systems which modify the smear layer and incorporate it into the bonding process.
Smear layer dissolving systems. Smear layer and underlying dentin partially demineralized by slightly acidic primers.
Smear layer moving systems. Smear layer is completely removed with acid conditioners
74
What does a dentine primer consist of and what does it do?
Consists of one or more molecules that have both hydrophilic and hydrophobic character.
Penetrate into demineralized collagen network to form hybrid layer.
Bond strength is related primarily to micromechanical bonding to intertubular dentin.
75
What is the bond strength defined as?
Load required to fraccture the bond divided by the cross sectional area. Fracture may take place in the bonded material, substrate, or both and may extend beyond the initial bonded area.
Force can be shear or tension
76
What makes bond strength hard to generalize?
Due to differences in materials
Bonding systems
Light-curing
Storage conditions
Substrate
Test methodology
77
What other materials does GIC need to be able to bond to?
Base metals (Ni, Co, Cr alloys)
Stainless steel, platinum and gold alloys which have been plated with a layer of tin oxide
Composite resins (sandwich technique)
78
What kind of procedure relies on the bonding of GIC to composite resins?
Sandwich technique
79
What are the advantages of the sandwich technique?
It combines the beneficial aspects of:
Composites - aesthetics
GIC - Adhesion to tooth structure and fluoride release
Reduces bulk of composite and subsequent polymerization shrinkage
80
What is the difference between open and closed sandwich technique?
Close: GIC is not exposed. Type II or III cement is used (base or liner)
Open: GIC is exposed, type II cement is used, type III cement at high powder:liquid ratio
81
What are the important clinical considerations to make with type II cements?
Wherever high stresses are involved, use type II cements.
Use a minimum cement thickness of 0.5mm
82
Is etching of GIC needed?
Etching dissolves the matrix leaving glass particles which roughens the surface, increasing the area available for attachments and allows resin to penetrate into the irregularities.
Need for this acid-etching is questioned because reliable bonding can be achieved through mechanical roughening/setting in air and application of resin.
No need for etching of resin-modified materials.
83
What is the effect of prolonged etching?
Causes excessive porosity and matrix dissolution
Detrimental to cement strength
84
What composites are selected for anterior teeth and non-carious cervical tooth loss?
Microfills due to better polishability and translucency. Also has a lower modulus of elasticity.
85
What composites are selected for posterior teeth?
Hybrids due to lower shrinkage and higher mechanical properties which are needed for forces involved in chewing.
86
What does a small particle size / high powder:liquid ratio indicate about a GIC?
It is stronger and forms a stronger bond to composite
87
What are the features to be considered with GIC when selecting what to use?
It is a fast setting cement.
When high radiopacity is required use type II.2 (metal-reinforced) cement
Where aesthetics is required, use type II.1 material. (Some type II.1 materials are also radiopaque)
88
How are glasses made radiopaque?
Calcium is replaced with barium or strontium.
89
How is GIC classified?
Powder:liquid ratio
Manufacturing process
Clinical applications
90
What are the types of GIC?
Type I - Luting cements
Type II.1 - Restorative aesthetic cement
Type II.2 - Restorative reinforced cement
Type III - Lining or base cement / pit and fissure sealants
All of these categories can be resin modified / reinforced (Dual or tri-cure, acid - base + polymerization reaction)
91
How is resin-modified GIC different to normal GIC?
Normal GIC is a cement that consists of a basic glass and an acidic polymer which sets by acid-base reaction between these components
resin-modified GIC consists of hybrid materials that retain a significant acid/base reaction as part of the overall curing process.
92
Why was resin used to modify GIC?
Resin-modified GIC was developed to overcome problems of moisture sensitivity and low early mechanical strengths associated with conventional GIC and at the same time maintain the clinical advantages.
93
What are the types of curing that resin-modified GIC can have?
Can be dual cure (acid-base + polymerization [light or chemically activated] or tri-dual cure (acid-base + polymerization reaction [light and chemically activated])
94
How is resin-modified GIC setting achieved?
Fundamental acid-base reaction is supplemented by a second polymerization reaction which may be light or chemically initiated.
This was achieved by:
Replacing water with water/HEMA mixture (hydroxyethyl methacrylate)
Replacement of polyacrylic acid (PAA) with modified PAA (modified PAA has side chains (pendant methacrylate groups) which can polymerize by light curing)
95
What is the purpose of the water/HEMA mixture?
They are 2 matrix forming reactions resulting in 2 matrices (separate phases)
Ionomer salt hydrogel
PolyHEMA
96
How is setting different in modified PAA?
Unsaturated groups can copolymerize with HEMA
PolyHEMA matrix will be chemically linked to polyacrylate matrix
Phase separation will not occur
97
How much resin is present in final set material?
4 to 6% and may be more in lining cements.
First RMGIC developed and marketed were lining cements
98
What are the advantages to using resin modified GIC?
Improved setting characteristics
A sufficiently long working time which can be curtailed on command to a snap-set by light curing
Rapid development of early strength
Less sensitive to water gain or loss.
Presence of resin matrix confers immediate resistance to water gain or loss, protection of exposed surfaces of the restoration with resin is advised but not critical
Improved adhesion to tooth structure
Chemical bonding to composite (sandwich technique)
Improved translucency
99
When should conventional cements be finished/polished?
24 hours later ideally.
100
Why is there improved adhesion of GIC to tooth structure as a result of resin modification?
Superior wetting ability of HEMA
Possibilty of micromechanical bonding
101
How does resin-modified GIC bond better to composite?
Residual methacrylate groups on PAA chain
Air-inhibited surface layer which polymerizes with composite
102
What are the disadvantages of using resin to modify GIC?
Setting shrinkage is higher
Depth of cure can be a problem
Physical properties can degrade during long-term exposure to moisture
103
How does resin-modified GIC look?
It is a handmixed powder-liquid (control over amount of cement, custom shading possible since powders can be blended)
Present in a capsule
104
Why is GIC present in a capsule?
Convenience
Consistent powder:liquid ratio
Elimination of variations associated with hand spatulation.
105
What are luting cements used for?
Cementation of crowns, bridges, inlays, and orthodontic appliances
106
What is the powder:liquid ratio of luting cements?
Powder:liquid ratio - generally 1.5:1
107
What are the features of luting cements?
Fast set with early resistance to water uptake
Small particle size for fine film thickness
Radiopaque
108
What are luting cements used for?
Cementation of crowns/bridges and inlays/onlays
109
When is cementation of crowns/bridges and onlays/onlays indicated in type I GIC usable?
Indicated in caries prone patients
110
What are possible causes of sensitivity following cementation of crowns/bridges and onlays/inlays?
Too thin a mix slows setting and prolongs low pH
Hydraulic pressure exerted in seating a tight crown
Prior bacterial contamination is caused by poor fitting provisional restoration
Open tubules caused by dentin conditioners (smear layer removal is not recommended by some people to reduce post-cementation sensitivity)
Dessication of dentin caused by excessive drying
Marginal leakage caused by early cleaning or washout of cement margins
Pre-existing pulpitis caused by existing pathology or traumatic tooth preparation
High occlusion
111
How can sensitivity following cementation of crowns/bridges and onlays/inlays be reduced?
Proper clinical technique will minimize potential causes of sensitivity
112
What are the advantages using luting cements?
Fluoride release
Adhesion to tooth structure and metal
Biocompatible
Thermal expansion similar to tooth
Low solubility in acids and oral fluids when set
High strength
113
What are the disadvantages using type I GIC?
High early solubility
Margins can be damaged by desiccation
Post-cementation sensitivity may be encountered
114
What are restorative aesthetic cements (type II.1) used for?
For any application requiring an aesthetic restoration; the only limitation is no undue occlusal load
115
What is the powder:liquid ratio of type II.1 restorations?
2.8:1 to 6.8:1
116
What kind of curing is done for type II.1 restoration?
Can be auto or dual-cure (through resin-modification)
Most autocure are radiolucent while most dual-cure are radiopaque
117
What are some examples of type II.1 cements?
Conventional: Fuji II (GC), Fuji IX, Ketac Fil
Resin-modified: Fuji II LC and photac Fil
118
What are the clinical applications of type II.1 cements?
Restoration of primary teeth
Restoration of permanent teeth:
Class I (ART)
Class II (ART, tunnel restorations)
Class III
Class V including non-carious cervical tooth loss
Repair of defective restoration margins
Temporary restorations
119
When are type II.2 cements used?
For use when aesthetic considerations are not important but a rapid set and good physical properties are required
120
What is the powder:liquid ratio for restorative reinforced cements?
3.1 to 4.1
121
What are the features of type II.2 restorative reinforced cements?
Fast set with early resistance to water uptake
Metal inclusions to improve physical properties (silver alloy, amalgam alloy)
Radiopaque
High early resistance to water contamination
122
What are examples of type II.2 restorations?
Ketac Silver (ESPE)
Chelon Silver
Hi-Dense (Shofu)
123
How are type II.2 cements made?
Addition of metal particles to conventional cements to form admixed restorative
High-heat sintering of silver ions to glass powder to form a cermet (ceramic-metal) material
124
What are the strength features of type II.2 restorations?
Designed to provide cements with considerably improved physical properties.
Bond strengths: Resin-modified > Conventional > Metal-reinforced
Physical properties: Tensile strength and fracture resistance marginally > than conventional GIC but less than RMGIC
125
How is type II.2 fluoride release compared to conventional GIC?
Similar despite metal inclusion
126
What kind of radiopacity does type II.2 GIC have?
Similar to amalgam due to presence of silver and silver alloys
127
What is the main application of type II.2 GIC?
Used mainly in areas of difficult access where a resin-modified GIC is contra-indicated and aesthetics don't matter:
Posterior primary teeth
Permanent teeth (Cl II - tunnel preparation)
Core build-up
Repair of defective restorations
Restoration of root surfaces for overdentures
Temporary restorations
Sealing of bifurcation areas in periodontally involved teeth
Retrograde root filling
128
What type of curing is used for lining or base cements?
Can be auto or dual-cure (through resin-modification)
129
What is the powder:liquid ratio of lining or base cements (Type III)? What does an increase in this ratio indicate?
Lining = 1.5:1
Base = 3:1
Physical properties improve as powder content increases
130
Are lining/base cements radiopaque or radiolucent?
Radiopaque
131
How are liners placed and what is their function?
Liners are placed with minimal thickness (<0.5mm)
Act as cavity sealers and provided expanded beneficial functions such as fluoride release and adhesion to tooth structures, antibacterial action that promotes health of the pulp
132
What are the functions of base cements?
Dentin replacement materials allowing less bulk of restorative materials or blocking our undercuts for indirect restorations
Can provide thermal insulation under metallic restorations
133
What are some examples of type III cements?
Conventional: Lining cement (GC)
Resin-modified: Vitrebond (3M) and Fuji lining LC (GC) [dual-cure]
134
What are the clinical applications of type III GIC?
Dentine liner under composites or amalgam
Liner over calcium hydroxide
Sealing of root canal before non-vital bleaching
Blocking of small undercuts in inlay/onlay/crown preparations
Sealing and filling of occlusal pits and fissures showing early signs of caries.
Bonding of orthodontic brackets
Bonding agent for composites
Root canal sealer
Bone cements and preformed implants for hard tissue replacement in otological surgery
135
What is the retention rate of type III GIC after 2 years? Is this a problem?
14 to 26%
Much lower in resin-based sealants (82%)
Complete retention of GIC sealants maynot be necessary for caries prevention
GICs have been ignored as fissure sealants which indicates more scope for development in this area
136
Why are type III sealants used rather than acrylic bone cements?
Lack of exotherm during setting, absence of monomer and improved release of therapeutic agents
Can form stable integration with bone and affect the growth and development of bone, both adjacent to their surface and systemically through an ion release mechanism
137
What is an important contraindication to using GIC?
Use of GIC in situations where they will come into contact with nerves or neural tissues is contraindicated
138
When is GIC used for ART?
Used for:
Isolated communities
Economically disadvantaged groups
House-bound elderly
139
How is ART performed?
Based on GICs ability to control caries and stimulate remineralization
Removal of undermined enamel and carious dentine in frank cavities using hand instruments only
Cavity is then filled with glass ionomer cement
Excess is removed and varnish is applied
140
What are the indications for ART?
Single-surface caries (Class I, III, and V cavities)
Multi-surface cavities (Class I and II cavities)
141
What are the contraindications of using ART?
Pulpal involvement
142
What is a tunnel restoration?
Placement of silver alloy mixed with sodium silicofluoride in the distal aspect of primary secondary molars to innoculate permanent first molar with fluoride as they erupted. This was modified to become a conservative technique for restoring small interproximal caries
143
How is the tunnel technique performed?
Adjacent tooth is protected with matrix band
Small round bur is used to gain entry via an occlusal fossa
Bur used to tunnel under marginal ridge towards interproximal carious lesion
GIC is injected into cavity (Type II.2 radiopacity)
Occlusal 1.5 to 2 mm of preparation is restored with composite
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What are the advantages of the tunnel technique?
Less potential for restorative overhang
Marginal ridge preserved
Smaller perimeter of restoration (less microleakage)
Less potential to damage adjacent tooth
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What are the disadvantages of the tunnel technique?
Highly technique sensitive
Preparation passes close to pulp
Visibility is decreased, caries removal is uncertain
Marginal ridge strength may be reduced
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How is close sandwich restoration completed? (Class I, II, III, IV, and V)
Cavity prep
Line or base with GIC (vitrebond)
Apply mixed cement to dentin surfaces of prepared cavity. Light cure for 30 seconds
Base (Fuji II LC):
Condition cavity using cotton pellet or sponge (GC dentine conditioner (10% polyacrylic acid) for 20 secs. GC cavity conditioner (20% polyacrylic acid) for 10 secs.
Wash and dry but do not dessicate dentine.
Mix one scoop powder; 2 drop liquids
Apply mixed cement to dentin surfaces of prepared cavity (0.75 mm thick)
Etch enamel and cementum (if present) for 15 seconds (SBMP etchant (35% phosphoric acid)
Wash and dry gently for 2 secs or blot dry (do not dessicate cementum and GIC)
Place transparent matrix and wedge
Apply primer to cementum if present. Dry gently for 5 seconds (Does no damage to enamel and liner/base)
Apply adhesive to enamel, liner/base and cementum (if present) light cure for 10 secs
Place ight-cure composite in increments
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How is an open sandwich restoration done? (Class II, III, and V)
Cavity prep
Place metal matrix and wooden wedge
Condition/prime cavity using cotton pellet/sponge or brush
Wash and dry but do not dessicate dentin/light cure primer
Activate capsule/mix cement
Inject mixed cement into cavity to cover cavosurface margins
Allow cement to set/light cure cement
Remove cement to allow for a laminate of composite (Expose sound enamel walls for acid-etch bonding. In the proximal box, cement should be removed to just below the contact area
Proceed as for closed sandwich technique
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How is restoration conducted for aesthetic (class III and V)?
Selection of product and shade:
Fuji II (auto-cure) or Fuji II LC (dual-cure)
Use encapsulated product if possible
Use non-encapsulated product when custom shading is desired
Slightly darker shade than desired because it becomes more translucent over 24 - 48 hours
Isolation of field (dry field necessary and use retraction cords to control bleeding and sulcular fluid)
Cavity preparation (caries removal with minimum thickness of 1mm)
Matrix selection (use whenever possible; transparent cervical matrix for class V, tin cervical matrix for class V, transparent celluloid strip for class III)
Clean tooth with pumice/water slurry
Pulpal protection in deep preparation close to pulp, place a hard setting calcium hydroxide
Dentin conditioning (condition dentin with cotton pellet or sponge)
Follow manufacturers instruction (GC dentine conditioner (10% polyacrylic acid) for 20 seconds or GC cavity conditioner (20% polyacrylic acid) for 10 seconds)
Wash
Hydrate the dentin surface (place a wet cotton pellet into the cavity and hydrate the dentine while mixing cement, do not allow contamination by saliva, blood, or sulcular fluid)
Remove wet cotton pellet and blot dry with a dry cotton pellet just before mixing of cement
Place with encapsulated cement or hand-mixed cement in a syringe
Inject glass ionomer into the preparation and place matrix firmly into place
Without matrix adapt with teflon instrument (if metal instruments are used wipe with alcohol or low viscosity resin to prevent cement pull-back
Finishing and polishing (Allow for initial set after 3 minutes before placing resin over it then ideally delay for 24 hours)
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Why are teeth isolated for GIC restoration?
Dry field is essential (pack retraction cords if necessary)
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How is cavity prepared for aesthetic GIC restoration?
Remove caries if present, minimum thickness of 1 mm of cement do not bevel enamel margins
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Conclusion:
GICs are based on an acid-base reaction between polyalkenoic acid and a calcium fluoro alumino silicate glass
In resin-modified GICs, the fundamental acid-base reaction is supplemented by a second polymerization reaction which may be light and/or chemical initiated
Key advantages to using GICs are fluoride release and long-term adhesion to tooth tissues
