1. Glass ionomer cement Dr. Gaurav Garg, Lecturer
Date: 29/1/2015
Asalaam Alekum
Glass ionomer cement
Dr. Gaurav Garg, Lecturer
College of Dentistry, Al Zulfi
Majmaah University

2. Contents Introduction Composition Classification Applications
Setting mechanism
Advantages
Disadvantages
Clinical Manipulation
References

3. Introduction
Glass ionomer is the generic name of a group of materials based on the reaction of silicate glass powder and polyacrylic acid.
Originally the cement was intended for the aesthetic restoration of anterior teeth, and it was recommended for use in restoring teeth with class III and class V cavity preparations.
Because of its adhesive bond to tooth structure and its caries prevention potential, the types of glass ionomers have expended to include their use as luting agents, orthodontic bracket adhesives, pit & fissure sealents, liners and bases, core build-ups, and intermediate restorations.

4. Composition Mostly supplied as Powder & Liquid
Two paste (Automix) forms are also available- Mainly Luting
Also available- Light cured, metal reinforced, Resin reinforced GICs

5. COMPOSITION Powder (Ion leachable glass) includes :
Silica (SiO2) – 35-50%
Alumina (Al2O3) – 20-30%
Aluminium flouride – (AlF3) 1.5 – 2.5 %
Calcium fluoride (CaF2) – %
Sodium Fluoride (NaF) – %
Aluminium phosphate (AlPO4) – 4.0 – 12 %
Lanthanum, Strontium, Barium in traces (for radio capacity)
Powder is about 20% fluoride by weight.
Particle size- typically 45 µm for restorative materials and 20 µm for luting materials

6. COMPOSITION Liquid : Polyacrylaic acid – 45% Itaconic acid – 5%
Maleic acid – 5%
Tricarballylic acid – 5%
Tartaric acid – Traces (increases working time and decreases setting time)
Water – 50% (Hydrates reaction product)

7. Classification

8. According to Wilson and McLean in 1988
Type I – Luting cements
Type II – Restorative cements
Restorative aesthetic
Restorative reinforced
B) According to application
1.Type I – Luting cements
2. Type II – Restorative cements
Aesthetic filling materials
Reinforced materials
3. Type III – Lining cement
4. Type IV – Fissure sealant
5. Type V – Orthodontic cement
6. Type VI – Core build up cement

9. 2. Anhydrous / water hardened
C) According to Liquid Composition
1. Hydrous
conventional glass ionomers use the polyacid in liquid form, they are hydrous.
These large molecular weight liquids can form complexes and thicken in the bottle, which reduces their shelf life.
2. Anhydrous / water hardened
freeze- or vacuum-dried polyacid usually added to the glass fillers to improve shelf life.
Distilled water is used as liquid
3. Semihydrous
Materials using both hydrous and anhydrous forms of polyacid in the same product
This combination provides intermediate liquid viscosities for luting and speeds the initial slow set associated with the anhydrous materials.
shelf life is somewhere between the hydrous and anhydrous forms.
Both have similar physical properties

10. Applications of GICs

11. Restoration of permanent teeth :
Class V and Class III cavities
Abrasion / Erosion lesion
Root caries
2) Restoration of deciduous teeth
Class I – Class VI cavities
Rampant caries, nursing bottle caries
3) Luting or cementing
Metal restorations viz. inlays, onlays, crowns
Non-metal restorations viz composite inlays and onlays
Veneers
Pins and posts
Orthodontic bands and brackets

12. Pit and fissure sealant
4) Preventive restorations
Tunnel preparation
Pit and fissure sealant
5) Protective liner under composite and amalgam
6) Core build up
7) Splinting of periodontally weak teeth
8) Glazing (Fuji Coat LC )
Glazing of traditional GIC filling
Improving aesthetics of old GIC filling
Protection of new GIC filling

13. Mechenism of Setting
Glass ionomers undergo three distinct and overlapping setting reactions.
Immediate ion leaching phase (immediately after mixing)
Hydrogel phase (initial set)
Polysalt gel phase (final set)
Once set, a glass ionomer consists of three components: a matrix, a filler, and a salt that attaches the filler to the matrix.
Mixing time: 45 to 60 seconds
Working time: 2 minutes
Setting time: 2 minutes
Total time: 4.5 minutes at 23 °C

15. lon-leaching phase
During this early phase, the glass ionomer adheres to the tooth structure.
It appears shiny or glossy from the unreacted matrix.
Placement should be completed in the early part of this phase, because the maximum amount of free polyacid matrix is available for adhesion.
At the end of this phase, as the material loses its shine; the free matrix reacts with the glass and is less able to bond to the tooth or any other surface.
Glass ionomers should not be manipulated once the initial gloss is gone.

16. Hydrogel phase
Begins 5 to 10 minutes after mixing, causes the initial set.
During this phase, the positively charged calcium ions are released more rapidly and react with the negatively charged aqueous polyanionic polyacid chains to form ionic cross-links.
The hydrogel phase reduces the mobility of the aqueous polymer chains, causing initial gelation of the ionomer matrix.
During this phase, the ionomer should be protected from moisture and desiccation.
The glass ionomer at this stage is rigid and opaque due to the large difference in the index of refraction between the, glass filler and the matrix.
This opacity is transient and should disappear during the final setting reaction.

17. Polysalt gel phase
Occurs when the material reaches its final set, can continue for several months.
The matrix matures when aluminum ions, which are released more slowly, help form a polysalt hydrogel to surround the unreacted glass filler.
The glass ionomer now looks more tooth-like because the index of refraction of the silica gel surrounding the glass filler is more similar to the matrix.

18. Advantages Adhesion to tooth structure High retention rate
Little shrinkage and good marginal seal
Fluoride release and hence carries inhibition (Anticariogenicity)
Biocompatible
Minimal cavity preparation required hence easy to use on children and suitable for use even in absence of skilled dental manpower and facilities

19. Disadvantages Brittle Soluble in oral fluids & acidic beverages
Low abrasion resistance
Water sensitive during setting phase
Less radiopaque
Less aesthetic than composite

20. Clinical Manipulation
Surface preparation
Preparation of the material
Placement / removal of the excess
Post operative restoration protection

21. SURFACE PREPARATION

22. CONDITIONING OF THE SURFACE WITH 25% POLYACRYLIC ACID

23. PRECONDITIONING SURFACE POSTCONDITIONING SURFACE

24. PREPARATION OF THE MATERIAL

25. Mouldable soft cervical bands
Adaptation of the band
Mouldable soft cervical bands
Placement of the GIC

26. Removable of the excess with sharp instrument like probe or scaler
POSTOPERATIVE RESTORATION PROTECTION

27. PREOPERATIVE VIEW
POSTOPERATIVE VIEW

28. References & Suggested reading
Sturdevant's art & science of operative dentistry Theodore M. Roberson, Harald O. Heymann, Edward J. Swift, Jr.
Principles of operative dentistry (2005)- A.J.E. Qualtrough, J.D. Satterthwaite, L.A. Morrow and P.A. Brunton.
Fundamentals of Operative Dentistry- 2nd Edition- Summitt & Robbins

29. THANK YOU!