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

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

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.

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

COMPOSITION Powder (Ion leachable glass) includes : Silica (SiO2) – 35-50% Alumina (Al2O3) – 20-30% Aluminium flouride – (AlF3) 1.5 – 2.5 % Calcium fluoride (CaF2) – 15-20 % Sodium Fluoride (NaF) – 3.0-6.0 % 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

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)

Classification

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

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

Applications of GICs

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

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

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

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.

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.  

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.

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

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

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

SURFACE PREPARATION

CONDITIONING OF THE SURFACE WITH 25% POLYACRYLIC ACID

PRECONDITIONING SURFACE POSTCONDITIONING SURFACE

PREPARATION OF THE MATERIAL

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

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

PREOPERATIVE VIEW POSTOPERATIVE VIEW

References & Suggested reading Sturdevant's art & science of operative dentistry-2006- 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

THANK YOU!