Glass Ionomer Cement Definitions & Classification PDF

Definitions Glass ionomer cements: It is an acid-base cement. It is supplied into powder and liquid that is to be mixed to give a mass that is used as a restoration or for cementing restorations.  Classification of GICs (According to use) Glass ceramics: Type I: Luting. Type II a: Esthetic r...

Definitions Glass ionomer cements: It is an acid-base cement. It is supplied into powder and liquid that is to be mixed to give a mass that is used as a restoration or for cementing restorations.  Classification of GICs (According to use) Glass ceramics: Type I: Luting. Type II a: Esthetic restoration. Type II b: Reinforced restoration. Type III: Lining or base.  Type I Luting cement for crowns, bridges and orthodontic brackets. Characterized by low P/L, thin film thickness & rapid set. Commercial brands:Ketac Cem (3M ESPE, Meron (VOCO), Riva luting (SDI), Medicem (Promedica) Type I  Type II a Esthetic restorative cement. Characterized by high P/L & good esthetics. Requires coting in the first 24 hours to protect from moisture. Commercial brands: Ketac Fil (3M ESPE), Riva Self Cure (SDI), Medifil (Promedica) Type II a  Type II b Reinforced restorative cement. Characterized by high P/L & good mechanical properties. Have early resistance to moisture contamination.  Type III Lining or base cement. Low P/L for lining & high P/L for base. Liner commercial brands: (Vitrebond (3M ESPE), Composeal & Medibond (Promedica), Fuji lining LC (GC). Type III Advantages of Glass Ionomer Cement: 1. Chemical bond with the tooth structure. 2. Fluoride release & recharge which makes it anti-cariogenic material. 3. Acceptable biocompatibility. 4. Esthetic appearance. 5. Good dimension stability (shows 3% contraction if properly manipulated). Dis-advantages of Glass Ionomer Cement: 1. Low mechanical properties. 2. Water sensitivity especially in the first 24 hours after mixing.  Modifications of glass ionomer cement: Mode of supply. Composition. Coating.  Modifications in mode of supply: 1. Capsule. 2. Water settable cement. 3. Paste-paste formula.  1. Capsule: It is loaded with the correct P/L & correct mixing Time which maximize the properties of the restoration. Dispensing throw the gun allows better adaptability. The final GIC showed less voids. Save time..  1. Capsule: Some capsule brands need to be activated using special activators before mixing, while others activated by pushing a bottom within the capsule.  2. Water settable cements: 1. The acid (polyacrylic acid) of the GIC liquid is freeze-dried then added to the powder of the GIC. 2. the mixing liquid is pure water or aqeous solution containing tartaric acid. 3. this formula has an extended working time as more time is required to dissolve the dried polyacrylic acid.  2. Water settable cement: Commercial brands for cement: Aqua meron (VOCO) & medicem aqua (Promedica). Commercial brands for restoration: A qua ionofil (VOCO), & medifil aqua (Promedica).  3. Paste-paste formula It is supplied in a clicker dispenser with 2 tubes. Each click dispenses the recommended ratio for mixing. Some brands dispenses 2 parts to be mixed with a spatula. Others supplied a mixing tip which delivers the cement mixed. Modifications of the composition: 1. Metal modified glass ionomer cement (Cermet). 2. Resin modified glass ionomer cements (RMGIC). 3. highly viscous glass ionomer cement (Packable glass ionomer). 4. Zinc reinforced glass ionomer cement. 5. Polyacid modified composite resin (Compomer). 6. Nano-ionomer. 7. Zirconomer.  1. Metal modified glass ionomer cement ( Cermet): Reinforcement of glass ionomer cement by sintering with a precious metal (such as silver) to the powder of GIC. Cermet chowed an increase in the mechanical properties. It shows decrease in esthetics, fluoride release & adhesion. It is used in posterior pediatric molars & as a core material.  2. Resin modified glass ionomer cement (RMCIC): Made by the addition of hydrophilic resin monomer, such as 2-hydroxyethyl methacrylate (HEMA), to the conventional GIC. It involves two setting reactions: i. Acid-base reaction. ii. Polymerization reaction (chemical, light or dual cured polymerization reaction). 2. Resin modified glass ionomer cement (RMGIC): RMGIC showed improved mechanical properties, less water sensitivity, fast working time, better handling properties little more esthetic than GIC. On the other hand, it showed less fluoride release.  3. Highly viscous glass ionomer cement (Packable glass ionomer): It is like conventional GIC but with reducing the amount of alkali ions on the expense of die & trivalent ions. This leads to more cross linking of the glass ionomer matrix.  3. Highly viscous glass ionomer cement (Packable glass ionomer): It is characterized by higher P/L , improved mechanical properties, less moisture sensitivity & faster setting time compared to conventional GIC. It showed lower fluoride release than conventional GIC.  4. Zinc reinforced glass ionomer cement: It is conventional glass ionomer cement with addition of zinc to the glass particles. Zinc is rapidly released from the glass particles after mixing. The divalent zinc ions lead to rapidly cross linking of the GIC matrix.  4. Zinc reinforced glass ionomer cement: It shows lower mechanical properties than RMGIC & HVGIC but with higher fluoride release. Commercial brand: Chemfil Rock (Dentsply). 5. Polyacid modified composite resin (Compomer): It is considered as a modification of composite resin. It is a light cured composite resin material with addition of glass ionomer component as a filler (glass particles & anhydrous polyalkenoic acid). 5. Polyacid modified composite resikn (Compomer): It is characterized by releases less amunt of fluoride than glass ionomer, no adhesion with tooth structure, less mechanical properties than composite resin (but higher than GIC). 6. Nano-Ionomer It is a modification of RMGIC. Zirconia/silica nanofillers & nanoclusters are added to the RMGIC. It shows comparable properties to RMGIC. Commercial brand: Ketak N100 (3M ESPE).  7. Zirconomer (White Amalgam) It is made y incorporating zirconia particles with the conventional glass ionomer. It shows better mechanical properties due to the transformation toughening of zirconia particles. It is supplied into two forms: 1. Zirconomer (opaque). 2. Zirconomer improved (translucent) due to addition of nano-zirconia particles. 7. Zirconomer (White Amalgam) 7. Zirconomer (White Amalgam) 7. Zirconomer (White Amalgam) Modification of Coating: Glass ionomer restorations need to be coated due to its early water sensitivity. Water is the reaction medium of the setting reaction of glass ionomer cement. Early loss or absorption of water weakens the glass ionomer cement matrix. Therefore, coating of glass ionomer restorations is a mandatory step. Modification of Coating: Many materials are suggested to coat the surface of glass ionomer cement such as; cocoa butter, bonding agent, & varnish. Manufacturer supplied many coat for glass ionomer cement which is light cured unfilled monomer (such as Fuji coat LC (GC) Final varnish LC (VOCO), & Copal varnish (Promedical). Modification of Coating: Modification of Coating: Recently, nanofilled coats are available in the market. The nanofillers increased the surface mechanical properties, surface gloss & seals the surface cracks & flaws so increasing the fracture toughness of the restoration. Commercially available nanofilled coats are G-coat plus (gc) & Easy Glaze (VOCO). Modification of Coating: