GIC


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Sehrish    on Oct 14, 2012 Says :

thnx
fussi    on Jan 12, 2012 Says :

thanks alott
anil    on Jan 09, 2012 Says :

Very useful in post dental care.
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1 : GLASS IONOMER CEMENT BY: Dr fussi ji Dept. of Pedodontics
2 : Glass ionomer cement It is group of materials based upon the reaction of silicate glass powder and polyacrylic acid. ISO terminology- polyalkenoate cement
3 : History GIC was developed by Wilson and Kent in England in the year 1972. The material has been in use in dentistry in Europe since 1975 and was introduced in US as ASPA (Alumino Silicate Poly Acrylate) in 1977. It is also known as Manmade dentin and dentin substitute because of its extensive use as a dentin replacement material.
4 : Classification According to Wilson and Kent: Type 1- Luting Cement Type 2- Restorative Cement (1) Restorative aesthetics (2) Restorative reinforced
5 : According to Mc Lean : GIC (traditional) Resin Modified GIC Polyacid modified composite resins.
6 : According to Application : Type I- Luting Cement Type II – Restorative Cement Type III- Lining Cement Type IV – Pit and Fissure Sealant Type V – Orthodontic Cement Type VI- Core Build up Cement Type VII- Pedodontic use Type VIII- Anterior Restorative Cement Type IX- Posterior Restorative Cement
7 : Composition POWDER Silica (SiO2) Alumina(Al2O3) Aluminium fluoride(AlF3) Calcium Fluoride(CaF2) Sodium fluoride(NaF) Aluminium phosphate(AlPO4) Lanthanum,Strontium, Barium for radioopacity LIQUID Polyacrylic acid Itaconic acid Maleic acid Tricarballylic acid Tartaric acid Water
8 : Tartaric acid acts as : - Hardener. - Controls the pH of cement during setting process. - Facilitates extraction of ions from the glass. -Increases working time and aids in snap set.
9 :
10 :
11 : Dispensing Supplied in multiple bottles of three or more shades. Cement is supplied in convenient pre-proportioned capsules form for mixing in mechanical mixers. These comes with nozzles for dispensing directly into the cavity from a gun.
12 :
13 : Setting Reaction It is basically an Acid- base reaction. GIC is formed by reaction of three materials A fluoroaluminosilicate glass powder. An ionic polymer of polyacrylic acid. water
14 : Reaction occurs between glass powder and ionic polymer and water acts as medium through which ion transfer takes place. When the powder and liquid are mixed, acid etches the outer layer of the glass particles, thereby releasing Ca, Al, Na, F ions. The Ca ions primarily react with polyacrylic acid and forms the cross linking with carboxyl ions on polymer chain to form reaction product i.e. Ca poly salts. This results in initial setting. Trivalent Al ions are released more slowly and replace the Ca ions within 24 hrs and forms the tighter network of cross link between polymer chain and is referred to as secondary reaction stage. The cross linked phase becomes hydrated over time with the same water used for mixing. This is called maturation.
15 : Na and F do not take part in the cross linking. Some of the Na ions may replace the H+ ions of carboxylic groups and the remaining ions are dispensed uniformly within set cement along with fluoride ions. Fluoride in the cement exists in dynamic relation with oral environment. There is a continuous leaching of fluoride throughout the life time of cement. The set cement consists of the agglomeration of unreacted powder particles surrounded by a silica gel in an amorphous matrix of hydrated Ca and Al poly salts.
16 :
17 :
18 : Role of Water It acts as a medium for reaction. At the stage of initial set the cement has to be protected from coming into contact with moisture as well as drying. If cement comes in contact, the Al ions are slowly leached out. This results in a weak cement as well as more soluble cement which will get eroded by oral fluids. If cement is dried,then water, which is essential for ion transfer, will prevent further progression of reaction.
19 : Mechanism of Adhesion Mechanism by which GIC binds to tooth structure is by chelation of carboxyl groups of poly acids with the Ca and/or PO4 present in hydroxyapatite of enamel and dentin. For proper adhesion there should be no smear layer present.
20 : Physical Properties Less stiff Solubility in water, during first 24 hrs is high. Coefficient of thermal expansion is similar to that of dentin. Inhibits bacterial growth. Biocompatible. Mild irritant to pulp tissue. Initially, pH- 2 then increases between 6 -7.
21 : Working time – 2 to 3 minutes. Mixing time- 45 to 60 sec Setting time- (a) Initial set- 5 to 7 minutes (b) Final set- 24 hrs.
22 : Other properties Senstivity to moisture. Post operative sentivity – associated with poor manipulation, poor P:L ratio, moisure contamination ( hydraulic effect of dentinal fluid) Aesthetics- compomers have better aesthetic as compare to light cure and traditional GIC.
23 : Clinical Placement of GIC Isolation Tooth prepration Cement placement Finishing and polishing Surface protection
24 : Isolation Saliva control is an essential step in restoration of GIC Other fluid like sulcular fluid should also be controlled. Use of rubber dam, retraction cords and cotton rolls with saliva ejectors is necessary.
25 : Tooth prepration Mechanical prepration Chemical prepration Mechanical Prepration - Prepration of the cavity, giving it the proper resistance and retention forms. Debriding – The bonding is enhanced by cleaned and conditioned surface. Use of pumice slurry to remove plaque and pellicle. Smear layer is removed by etching with phosphoric acid (34% - 37%).
26 :
27 : Chemical prepration- (conditioning) Conditioning is done by organic acid like polyacrylic acid (10% – 20 %) for 10- 20 sec. After conditioning and rinsing, the surface is dried, but should not be dessicated.
28 : Cement placement Mixing of the cement Capsulated cement – used with syringe technique Hand mixing technique- mixing can be done either on paper pad of a glass slab using agate or plastic spatula.
29 : Powder is dispensed first on slab and divvied into two halves. Then the liquid bottle is tilted at 90 degree to allow the liquid to displace air through the nozzle and occupy nozzle. Then the bottle is tilted vertically and squeezed to dispense the required ratio of liquid. Only one drop at a time without inclusion of air bubble. Powder-liquid ratio Dispensing the powder Dispensing the liquid
30 : As the powder was divided into two halves, the first half of the powder is first properly mixed by rolling the powder into the liquid. After mixing the first half with agate spatula, the other half is mixed in the same manner i.e. rolling motion.
31 : Restoration- Cement after mixing is carried in one bulk for placement into cavity without entrapment of air bubbles. Finishing and polishing Initial contouring Final polishing is done after 24 hrs, with the help of discs of different gradation of abrasives from coarse to fine. Metal finishing strips
32 : Surface Protection Enamel bonding agents provides best surface protection. Newly placed cement should be sealed immediately after removal of matrix to prevent water exchange. If surface is not protected during maturation, it will lead to the crack formation at the surface. Surface cracks
33 : Clinical applications Luting cement- GIC is used for luting all crowns and bridges. Used because of its: anticariogenic property, low solubility, pulp compatibility, low film thickness.
34 : As Restorative cements- (a) Lesions at cervical margins of teeth. (b) Abrasion-Erosion lesion with caries (c) Abfraction lesions (d) Class III cavities
35 : As restorative for deciduous teeth- It is used as a restorative material for deciduous teeth because of their high fluoride release and minimal cavity prepration requirement. GIC is now widely used for primary carious tooth. As lining cement- A lining is designed under a metallic restoration, to provide thermal protection to pulp. It has limited physical properties. So, it cannot be used in cases of sandwich technique.
36 : As pit and fissure sealants- It has more fluid consistency to flow into depths of pits and fissures of posterior teeth. As orthodontic Bracket adhesive- They bind directly to tooth tissues by interaction of polyacrylate ions and hydroxyapatite crystals, thereby avoiding acid etching and have anticariogenic effect. Though now less in use due to its low bond strength.
37 : For core build up- Used for core build up due to: (a) apparent ease of placement, (b) adhesion, (c) fluoride release and (d) matched coefficient of thermal expansion. For intermediate restoration- It is used in abrasion cavities, cervical abrasion cavities because of their inherent adhesive nature and satisfactory adhesives. Used in laminate technique- Also known as sandwich technique. In this technique, the layer of GIC is placed beneath the composite restoration, due to its better adhesion to the dentin than composites.
38 :
39 : Modifications of GIC Metal reinforced GIC Highly viscous conventional GIC Resin modified GIC (hybrid ionomer) Tri-cure GIC Compomer Ceramic reinforced GIC (amalgomer) Light curing restorative GIC (nano ionomer) “Anhydrous” GIC Giomer Ormocer
40 : Refrences Phillips science of DM by Kenneth J.Anusavice Dental Materials-properties by Robert Craig Textbook of Pedodontics by Shobha Tandon Art and science of operative dentistry by Sturdevant’s Textbook of operative dentistry by Vimal K Sikri
41 : Thank You

 

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