glass ionomer Metal-Modified GIC Resin-Modified GIC dental material

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glass ionomer Metal-Modified GIC Resin-Modified GIC dental material

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glass ionomer Metal-Modified GIC Resin-Modified GIC dental material

  1. 1. GLASS-IONOMER CEMENT Acid-Base Reaction Cements:
  2. 2. Glass-Ionomer Cement  The word glass-ionomer is a generic name derived from material’s composition  The powder is ion-leachable glass (Calcium- flouro-alumino-silicate) that is able to react with ionomeric acid containing carboxyl groups (e.g. Poly acrylic acid)  Sometimes the name Polyalkenoic cement is used
  3. 3. General Applications  Final cementation  Cavity base and liner  Esthetic Filling material (in eroded cervical lesions)  Bonding agent  Fissure sealer  Endodontic sealer  Filling of deciduous teeth  Amalgam Bonding
  4. 4. Cementation of orthodontic brackets
  5. 5. Classification of G.I. cements A. According to the use  Type I: Luting material (P.size < 15 m)  Type II: Esthetic Filling material (P.size =20-50 m)  Type III: Cavity base and liner B. According to The curing mechanism  Chemical-cured: Cement sets via acid-base reaction  Dual-cured: Cement sets via both polymerization and acid-base reactions  Triple-cured: Cement sets via chemically-activated polymerization, light-activated polymerization and acid-base reactions
  6. 6. Classification of G.I. cements C. According to the modification  Conventional GI: No modification -- Sets via acid-base reaction  Metal-modified: Ketac silver and Cermet--Sets via acid-base reaction  Resin-modified:-- Either dual or triple-cured
  7. 7. Presentation forms 1. Powder-liquid - To be mixed using plastic spatula over paper pad 2. Water-settable powder - Dry powder of PAA copolymer is blended with cement powder in the same bottle. - The material is mixed with regular water 3. Capsules - Both cement powder and liquid are contained in the same capsule and separated from each other by a diaphragm 4. Two-paste system - Recently introduced as a cement (luting material) material. - Equal lengths to be mixed over a paper pad
  8. 8. Conventional G.I. cements Composition  Powder: 1. Calcium-fluoro-alumino-silicate glass particles - All compositional ingredients (CaF2, Al2o3, Sio2, NaF, AlPo4) are fused together at 1100-1500oC  ingot then grind into the desired particle size 2. Radio-opaque glass particles in which barium or strontium replaces the calcium
  9. 9. Conventional G.I. cements Composition  Liquid: 1. Aqueous solution of Poly-alkenoic acid - PAA or its copolymer with maleic or itaconic acid - Sometimes the acid may present in the dry powder form to be blended with cement powder in case of water-settable material 2. Tartaric acid To  viscosity of PAA and to  the setting time
  10. 10. Conventional G.I. cements Setting reaction  Chemical reaction of acid-base type  H+ from the acid attacks the aluminum sites  Decomposition of the surface of glass particles  Release of Ca++ and Al+++ ions into the aqueous medium  the Ca++ and Al+++ cross-link the poly acrylate chains by forming poly-acid sol (initial setting)  the sol transfers into poly-acid gel forming cement matrix (hardness and strength)  surface of the un-reacted glass particles is coated with a layer of silica gel
  11. 11. Conventional G.I. cements Setting reaction  The set material is composed of;  Non-reacted powder coated with silica gel in an amorphous matrix of hydrated poly- acid salts (gel (Calcium and aluminium poly-acid gel)  Water is a component of the set material. The loosely bonded water could evaporate out of the material  desiccation and contraction  Fluoride ions remain free, and released only when the material becomes wet
  12. 12. Conventional G.I. cements Manipulation 1. Mixing • Mixing is achieved over a paper pad using plastic spatula • Stainless steel spatula is contraindicated to avoid the contamination of mix by the abraded metal particles • Large amount of powder is incorporated into the liquid at once • Thin mix  cementation • Thick mix filling or cavity base 2. Tooth should be cleaned or even conditioned by PAA before cement application
  13. 13. Conventional G.I. cements Manipulation (Cont.d) 3. Restorative material • Should be inserted as one bulk into the cavity • The excess is removed after partial setting using sharp hand instrument • The material left to set in 24 hrs and then finished 4. Surfaces of fillings or margins of cement should be protected from saliva by applying varnish or resin coating 5. Recoating is strongly recommended after finishing and polishing
  14. 14. Characters of conventional G.I. cements 1. Biological properties • Freshly-mixed cement may cause mild or moderate pulp irritation, accordingly deep cavities should be lined with calcium hydroxide • The material provides chemical bonding to both tooth structure and restoration surfaces -->  the rate of microleakage • The fluoride release --> help in  the rate of caries recurrence 2. Interfacial properties  The material is chemically-bond to the apatite part of the tooth, base metal alloys and tin-plated gold alloys
  15. 15. 3. Chemical properties • The set G.I. cement is more resistant to solubility in oral fluids than other cements based on the acid-base reaction • However, fresh cement is easily soluble in saliva and the material should be protected either with resin or varnish coating 4. Mechanical properties  The cement is stronger on compression than other zinc-oxide based cements  However, the set material is brittle having low DTS and fracture toughness Characters of conventional G.I. cements
  16. 16. 5. Esthetic properties • The set G.I. cement is translucent and could be used to cement ceramic restorations 6. Thermal properties  The cement has low thermal diffusivity and could be used as cavity base under amalgam restorations 7. Practicability  The cement is easily mixed on paper pads using only non-metallic spatulas Characters of conventional G.I. cements
  17. 17. 7. Practicability (Cont.d)  Cleaning and conditioning of tooth surfaces together with using the freshly-mixed material all improve the bond  The material could be used as a liner under composite restorations (Sandwich technique)  Restorative material should be applied as one piece while filling tooth cavities (bulk filling technique) as the increments do not cohere together  Resin or varnish coating is required to protect the setting material  Careful and delayed (after 24 hrs) finishing should followed with resin or varnish coating Characters of conventional G.I. cements
  18. 18. Metal-Modified Glass-Ionomer Cements Inclusion of metal particles within the composition or the structure of cement’s powder
  19. 19.  Cement powder is a simple blend of regular glass and amalgam particles  The blend is reacted with regular cement liquid (PAA)  The mixed material sets via acid-base reaction typically as that of the conventional glass-ionomer 1. Ketac Silver  Characters of the modified material - Shows a little bit higher strength than that of Conventional G.I. - Shows an increased rate of solubility - Become opaque with gray metallic color - Used to fill the primary molars
  20. 20.  A small amount of silver is fused with cement’s glass particles at the time of manufacturing  The resulted particles react with regular cement liquid (PAA) and the mixture also sets via acid-base reaction typically as that of the conventional glass- ionomer  Characters of the modified material - Shows higher strength and better resistance to wearing than the conventional G.I. - The material is also opaque having gray metallic color - Used for core build-up and as posterior filling in selected cases 2. Cermet
  21. 21. Resin-Modified Glass-Ionomer Cements (RMGI) Inclusion of resin monomer to form (after its polymerization) a protective matrix in which the regular cement setting takes place The resultant material owns a dual mechanism of setting that includes both polymerization and acid-base reactions Dual-cured Cements:
  22. 22. A. Powder  Alumino-silicate glass particles  Polymerization initiator  Chemical initiator (Benzoyl peroxide) in case of chemically-activated polymerization  Photo-initiator (Camphroquinon) in case of light- activated polymerization  Both in case of triple-cured materilas A. Liquid  Aqueous solution of Poly-alkenoic acid  Poly-acrylic acid having some carboxylic groups modified with methacrylate or HEMA monomer Composition of RMGI
  23. 23.  The initial and rapid setting of the material is provided through polymerization of resin monomer  Slow acid-base reaction also takes place within the cured resin matrix. This reaction is responsible for maturing process and the final strength  The water content is too little to complicate the polymerizaton, however its presence is essential for the acid-base reaction. Setting of RMGI
  24. 24. The modification provides material having  Higher strength and fracture toughness than that of conventional G.I.  Lower solubility of the freshly-set material  Possibility for immediate finishing and polishing  No need for resin or varnish coating  Lower rate of fluoride release Characters of RMGI
  25. 25.  Esthetic filling materials in non-stress bearing areas, cervical erosions  Fissure sealant  cavity base and liner  Bonding agent  Core building-up material  Cement for ceramic restoration Applications of RMGI
  26. 26. Continuum of Esthetic Restoratives Composite Compomer Giomer RMGI GI
  27. 27. CEMENTS SET BY POLYMERIZATION REACTION A. Resin composite cement B. Resin compomer cement Note.  Composite = Resin matrix + inorganic fillers + coupling agent + polymerization initiator  Compomer = polyacid-modified composite resin
  28. 28. A. RESIN COMPOSITE CEMENTS  Firstly developed in the early 1970s to be used with adhesive/ resin bonded bridges  They are less heavily-filled composites (filler load = 65%)  These materials set via polymerization reaction  Present materials can be classified according to its mode of polymerization into chemical-cured, light-cured, and dual-cured
  29. 29. RESIN COMPOSITE CEMENTS A. Chemically-cured composite cement  Many types contain on 4-META (4-methacryloxy ethyl trimellitic anhydride), that provides good bonding to several metal alloys  Used for; 1. Cementation of resin-bonded bridges 2. Cementation of any metal restoration (inlay, onlay, crown) 3. Placement of bonded amalgam restoration
  30. 30. RESIN COMPOSITE CEMENTS B. Visible light-cured composite cement  VLC materials utilize a polymerization system similar to that of VLC composites  These materials are available in different shades to help in production of good esthetics  Some manufacturers provide a try-in pastes have the same color shade of actual cement (water- soluble paste used during try-in stage)  Used for luting ceramic veneer
  31. 31. Cementing ceramic veneers Labial veneer Palatal surface Resin composite cement Labial gingiva
  32. 32. RESIN COMPOSITE CEMENTS C. Dual-cured composite cement  Dual-cured materials could be polymerized by both light or chemical activation (i.e. polymerized even if they do not receive sufficient light)  Usually supplied as two-paste system, one of them are used to determine the shade  Used for luting composite and ceramic inlays, endodontic posts, and ceramic crowns
  33. 33. RESIN COMPOSITE CEMENTS ADVANTAGES:  Low solubility in oral fluids (resin-based material)  Good strength properties (presence of fillers)  Low film thickness (low filler loading)  Good esthetics (color shade and color stability) DISADVANTAGES:  Poor wear resistance than regular composites  Require the use of bonding agent  Material’s polymerization could be affected in presence of moisture or oxygen …… the exposed cement margins should be coated with air-inhibition gel
  34. 34. B. RESIN COMPOMER CEMENTS A kind of resin-based cement, used to cement cast and metal-ceramic restorations COMPOSITION:  Powder: Alumino-fluoro-silicate glass, sodium fluoride, self and/or light-cured initiator  Liquid: Methacrylate-carboxylic acid monomer, diacrylic monomer, water
  35. 35. RESIN COMPOMER CEMENTS ADVANTAGES:  Provide chemical bonding to tooth structure….. through the present carboxylic acid groups of the monomer  Fluoride release help in inhibition of recurrent caries  High compressive and flexure strengths = composite cement  Higher fracture toughness > glass-Ionomer cement
  36. 36. Self-etching self-adhesive resin cements  All types of resin cements require etching, application of bonding agent to the surfaces (tooth & restoration) to be cemented  These new kind of resin-based cements contain phosphate-based monomer that have the ability to etch and chemically bond to tooth structure

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