Post on 07-May-2015
Glass ionomer cement
INTRODUCTION
Glass ionomer cement is a tooth coloured material, introduced by Wilson & Kent in 1972.
-a.k.a glass polyalkenoate
Silicate Glass Powder
Polyacrylic acid
GIC
CLASSIFICATION
Type I. For lutingType II. For restoration
Type II.1 Restorative esthetic Type II.2 Restorative reinforced
Type III. For liner & basesType IV. Fissure & sealentType V. As Orthodontic cementType VI. For core build up
COMPOSITION
Powder:Acid soluble calcium fluroalumino
silicate glass.Silica - 41.9%Alumina - 28.6%Aluminum fluoride - 1.6%Calcium fluoride - 15.7%Sodium fluoride - 9.3%Aluminum phosphate - 3.8%Fluoride portion act as ceramic flux.Strontium, barium or zinc oxide
provide radio opacity.
Liquid:1.Polyacrylic acid in the form co-
polymer with itaconic acid & maleic acid .
2.Tartaric acid: improves handling characteristic
& increase working time.3.Water : Medium of reaction &
hydrates the reaction products
SETTING REACTION
When the powder & liquid are mixed, surface of glass particles are attacked by acid. Then Ca, Al, sodium, & fluoride ions are leached into aqueous medium.
Calcium poly salts are formed first, then followed by aluminum poly salts which cross link with poly anion chain.
Set cement consist of unreacted powder particle surrounded by silica gel in amorphous matrix of hydrated calcium & aluminum poly salts.
Calcium poly salts are responsible for initial set.
Aluminum poly salts form the dominant phase.
Water plays an important role in structure of cement.
After hardening, fresh cement is extremely prone to the cracking & crazing, due to drying of loosely bound water .
Hence these cements must be protected by application of varnish.
SETTING TIME
Type I 4 - 5 minutes
Type II 7 minutes
PROPERTIES
Handling characteristics: Previous versions of GIC had problems
with inappropriate working and setting time. Tartaric acid inclusion resulted in: ▪ Tartaric acid reacting with calcium as it was
released which extends working time to reasonable values
▪ Enhances rate of formation of aluminum polyacrylate crosslinks which speeds up setting.
Solubility and disintegration:
Initial solubility is high due to leaching of
intermediate products.
The complete setting reaction takes
place in 24 hrs, cement should be
protected from saliva during this period.
Adhesion: Glass ionomer cement bonds chemically
to the tooth structure. Bonding is due to reaction occur
between carboxyl group of poly acid & calcium of hydroxyl apatite.
Bonding with enamel is higher than that of dentin, due to greater inorganic content.
Esthetics: GIC is tooth coloured material &
available in different shades. Inferior to composites. They lack translucency & rough
surface texture. Potential for discolouration &
staining.
Biocompatibility: Pulpal response to glass ionomer cement is favorable.
Pulpal response is mild due to ▪ High buffering capacity of hydroxy apatite.
▪ Large molecular weight of the polyacrylic acid , which prevents entry into dentinal tubules
Anticariogenic effect: Fluoride is released from glass
ionomer at the time of mixing & lies with in matrix. Fluoride can be released out without affecting the physical properties of cement.
Initial release is high. But declines after 3 months.After this, fluoride release continuous for a long period.
Fluoride can also be taken up into the cement during topical fluoride treatment and released again ,thus GIC act as fluoride reservoir.
Strength: Compressive strength - 150 mpa Tensile strength - 6.6 mpa. Hardness - 49 KHN.
ADVANTAGES:
♣ Inherent adhesion to the tooth surface.
♣ Good marginal seal.
♣ Anticariogenic property.
♣ Biocompatibilty♣ Minimal cavity
preparation required.
DISADVANTAGES:
♦ Low fracture resistance.
♦ Low wear resistance.
♦ Water sensitive during setting phase .
♦ Less esthetic compared to composite.
USES
1. Anterior esthetic restoration material for class III & V restorations.
2. For luting.3. For core build up.4. For eroded area .5. For atraumatic restorative
treatment.6. As an orthodontic bracket adhesive.7. As restoration for deciduous teeth.8. Used in lamination/ Sandwich
technique.
CLINICAL USE
For luting: Advantages:
▪ Fluoride release▪ Low film thickness▪ Kind to pulp▪ Bond to tooth structure
Their use decreased after hybrid ionomers and resin cements were introduced since they are stronger
As restorative material: used in non-stress bearing areas:
▪ Root caries▪ Occlusal lesions in primary teeth▪ Temporary restorations▪ Cervical cavities (abrasion and erosion
lesions)▪ Anterior class III when color matching
is not an issue
As liners and bases: used to protect the pulp from:
▪ Temperature changes▪ Chemicals from other restorative materials▪ Acid etchants
Liners have lower powder: liquid ratio and weak.
GIC bases are used to rebuild missing tooth structure, stronger than liners and have a higher powder: liquid ratio
As pits and fissure sealants: The use of GICs as sealants have been
suggested due to:▪ Fluoride release.▪ Adhesion to moist tooth structure
Disadvantages:▪ Inability to fully penetrate fissures▪ Brittleness▪ Low wear resistance
Core build up materials: cermet GICs are usually used for
this purpose. They are used:▪ In locations were esthetics are not
important▪ To replace missing tooth structure
where the permanent restoration is crown.
SANDWICH TECHNIQUE
Devolped by Mclean,To combine the beneficial properties
of GIC & composite.
An effective technique for both anterior and posterior resin based restorations.
For pulpal protection from the acid-etch technique.
And as a mechanism for sealing the cavity in the absence of good dentin adhesion available with the materials of the time.
Clinical steps: After cavity preparation, condition the cavity
to develop good adhesion with GIC. Place Type III GIC into prepared cavity. After setting, etch the enamel & GIC with
orthophosphoric acid for 15 seconds. This will improve micromechanical bond to composite resin.
Apply a thin layer of low viscosity enamel bonding agent & finally place the composite resin over GIC & light cure it.
Advantages: Polymerisation shrinkage is less,due to
reduced bulk of composite. Favorable pulpal response. Chemical bond to the tooth and
composite increasing retention form. Provides better seal when used at
nonenamel margins.
Advantages: Anticariogenic property Potential for recurrent caries low. Decreased microleakage and gap
formation. Better strength, finishing, esthetics of
overlying composite resin.
Advantages for the flowable composite:
(as a liner under a composite) Acts as a shock absorber, distributing
stresses applied to the more rigid composite.
Reduce some of the negative effects of polymerization shrinkage.
TWO TECHNIQUES:1. Closed Technique- The traditional technique.-Involves the placement of GIC at the base of the proximal box so as it falls just short of the external cavo surface. After setting, the GIC is etched with phosphoric acid and dentin bonding agent is applied before placing composite resin into the proximal box and occlusal surface.
2. Open Technique- Involves the placement of GIC into the base of a proximal cavity and filling the preparation with glass ionomer upto the DEJ. The last portion of the restoration is placed with composite resin to provide wear resistance and esthetics on the occlusal surface.- For clinical situations where a portion of the restoration would have a dentin only margin (as in a deep class II or a class V on a root surface).
- Advantage of Open Technique:a. The large area of GIC available for buffering any changes in acidic pH.
-Disadvantage of Open Technique:b. Over time the GIC succumbs to acid breakdown over the surface resulting in food packing and recurrent caries within glass ionomer.
Factors necessary for successful tooth restoration: Removal of infected dentin and enamel
completely Treating the enamel and dentin
appropriately with bonding materials. Manipulating properly the to-be-bonded
restorative material. Contouring the restoration to provide
proper form and function.
Advantages: Polymerisation shrinkage is less,due to
reduced bulk of composite. Favorable pulpal response. Chemical bond to the tooth. Anticariogenic property Better strength, finishing, esthetics of
overlying composite resin.
GIC MODIFICATIONS
1. Water settable glass ionomer cement:
Liquid is delivered in a freeze dried form, which is incorporated into the powder.
Liquid used is clean water.
Advantages: low viscosity in the early mixing stages improved shelf Improved strength
2. Resin modified glass ionomer cement:
Resin composite + conventional GIC Powder component consist of ion
leachable fluroalumino silicate glass particles & initator for light curing.
Liquid component consist of water & poly acrylic acid with methacrylate & hydroxyl ethyl methacrylate monomer.
Advantages: greater working time command set on application of visible
light good adaptation and adhesion acceptable fluoride release aesthetics similar to those of composites superior strength characteristics
Disadvantages: setting shrinkage limited depth of cure especially with
more opaque lining cements.
3. Metal modified glass ionomer cement: Glass ionomer have been modified by addition
of filler particles to improve strength , fracture toughness & resistance to wear.
Silver alloy mix / miracle mix:- This is made by mixing of spherical silver
amalgam alloy powder with glass ionomer powder.
Cermet: Bonding of silver particles to glass ionomer
particles by fusion through high temperature sintering.
Cermets Grey in color Greater value of compressive strength
and fatigue limit than conventional glass ionomers
Flexural strength and resistance to abrasive wear appear no better than values recorded for conventional GIC
Rapid setting improved erosion resistance
Lower Fl release
4. GiomerIt is basically a modified Glass
Ionomer. It is a hybrid of Glass Ionomer and
Composite.The GIOMER concept is based on the
novel PRG (Pre-Reacted Glass Ionomer) technology, where special PRG fillers are included in the resin matrix which differs it from Compomer making it possess both properties of Composite and Glass Ionomer.
PRG technology is used in production of two types of fillers. S-PRG(Surface Pre-reacted GI) eg.
Beautiful by Shofu F-PRG(Full Pre-reacted GI) eg. Reactimer
by shofu
Properties Fluoride release Esthetics (shade conformity) Ease in Polishing Strength (resistance to wear) High radiopacity Anti-Plaque Effect Biocompatibility Long term clinical stability
Composition Bisphenol A Glycidyl Dimethacrylate TEGDMA Inorganic Glass Filler Aluminuoxide Silica PRG filler DL-camphorquinone
Indications Diastema Closure Discoloration Non-Carious Defect(attrition/ abrasion/
surface defects Carious Defect Fracture Malformation Faulty and Old Restoration
Diastema closure
Discoloration
Non-Carious Defect(attrition/ abrasion/ surface defects
Carious defect
Fracture
Malformation
Faulty and old restoration
Compomer These are recently introduced products
marketed as a new class of dental materials.
These materials are said to provide the combined benefits of composites (the “comp” in their name) and glass ionomers (“omer”).
These materials have two main constituents: dimethacrylate monomer(s) with two
carboxylic groups present in their structure and
filler that is similar to the ion-leachable glass present in GICs.
The ratio of carboxylic groups to backbone carbon atoms is approximately 1:8.
There is no water in the composition of these materials, and the ion-leachable glass is partially silanized to ensure some bonding with the matrix. These materials set via a free radical polymerization reaction, do not have the ability to bond to hard tooth tissues, and have significantly lower levels of fluoride release than GICs.
Although low, the level of fluoride release has been reported to last at least 300 days.
They do not set via an acid-base reaction and do not bond to hard-tooth tissues, they cannot and should not be classified with GICs.
Properties Fluoride release, Radiopaque, Quick cure time and Good handling characteristics (no slumping, easy
to shape/polish, no sticking) Can be light-cure or self-cure Packaging can be unit dose (capsule) or multi-
dose (syringe) Curing time: 10-20 secs (depending on brand) Esthetics
Indications Deciduous teeth Cervical defects
Disadvantages Lower flexural modulus of elasticity, Compressive strength, Flexural strength, Fracture toughness and hardness, Higher wear rates
References
Davidson, C. (2009) Advances in glass-ionomer cements. Journal of Minimum Intervention Dentistry.
Forsten L. Fluoride release of glass ionomers. J Esthet Dent 1994; 6:216-22.
Forsten L. Resin-modified glass ionomer cements: fluoride release and uptake. Acta Odontol Scand 1995; 53:222-5.
McCabe, J. and Walls, A. Applied Dental Materials 9th edition Chap.24 pp.245-256
Millar BJ, Abiden F, Nicholson JW. In vitro caries inhibition by polyacid-modified composite resins (‘compomers’). J Dent 1998; 26:133-6.
Nagaraja Upadhya P and Kishore G. (2005) Glass Ionomer Cement – The Different Generations. Trends Biomater. Artif. Organs, Vol 18 (2)
Thank you!