GLASS IONOMER CEMENTS dr shabeel pn
INTRODUCTION • GIC is an adhesive tooth coloured restorative material used for eroded areas and now it has been used for other areas also . • Salt formed by reaction between poly alkenoic acid and • Calcium aluminoflurosilicate glass .
HISTORY developed by Wilson & Kent in 1972 . Yogi etal - 1992 – GI cement is used as a sealent for partially erupted permanent molars . Groll etal – 1993 – Recommended light curable glass polyalkeonate for amalgam replacement . Althadaing etal - 1994 – light cured glass ionomer for repairing furcated areas on the pulpal floor . Thevadans etal – 1996 – Mixing of 4 % NaF with GIC. .
Also named as…… • polyalkeonates . • ASPA (aluminosilicatepolyacrylic acid ) developed by Wilson etal 1970 . .
ADVANTAGES • Tooth coloured material . • It will adhere directly to both enamel and dentine through ion exchange mechanism . • Biologically active as it is capable of releasing fluorides , calcium and phosphate .
CLASSIFICATION TYPE I - Luting TYPE II – Resoration . TYPE III – Liners and bases . TYPE IV - Pit and fissure sealants . TYPE V – Orthodontic cements . TYPE VI – Core built up.
CLASSIFICATION…… • TYPE I - Luting • TYPE II - Restoration • TYPE III - Liners & Bases • TYPE IV - Resin modified • TYPE V - Metal modified • TYPE VI - Ceromers • TYPE VII - Compomers • TYPE VIII - Geriatric • TYPE IX - Pediatric
CLASSIFICATION BY G J MOUNT Based on the - water powder ratio. physical properties . clinical application . TYPE I – Luting agents . TYPE II i – Esthetic restoration . TYPE II ii – Non esthetic restoration . TYPE III - Liners and bases .
CLASSIFICATION NO:3 TYPE I Conventional TYPE II Restorative Class 1 – esthetic restorative cements . Class 2 – reinforced restorative cements or metal modified glass ionomer . TYPE III Light cured lining glass ionomer cement ( liners and bases ) .
TYPE I –CONVENTIONAL GI. • Mostly used in cementing , luting , liners and bases . • Powder particle size – 15 micron . • Thickness of cement film – 2 micron . • Thin pulpal dentin is required to be protected • with hard Setting Ca ( OH )2 .
TYPE II RESTORATIVE GIC Class I esthetic restorative cement Mostly used for anterior restorations Class II reinforced restoration cements
Class I reinforced restoration cement ( metal modified , posterior GI) Mostly used for posterior restorations . A ) Amalgam alloys mixed with cements. B ) Cermet ( ceramic metal mixture ) Glass powder is fused and sintered with Ag particles .
PROPERTIES • Resistance to wear as they are stronger and tougher . • Poor esthetics due metallic color • Less pulpal irritation . • Posses anticariogenic properties
TYPE 3 a – Light cured lining glass ionomer cements HEMA ( hydroxy ethyl methacrylate ) added to light component . Reduce shrinkage . To increase strength , powder mixed with alumino – silicate glass.
TYPE 3 b – Light cured glass ionomer cement COMPOSITION POWDER - ion leachable glass . LIQUID - Polyacrylic acid or Polyacrylic acid with HEMA . SETTING REACTION Initial set – polymerization of methacrylate gp Final set – slow acid – base reaction
PROPERTIES Reduced translucency . Increased tensile strength Stronger adhesion to teeth surface . Decreased marginal adaption and increased marginal leakage due to polymerization shrinkage .
TYPE 4 Hybrid resin modified G I • Used as restorative filling material. • HEMA added to liquid component - bonding. • Have higher resistance to wear & tear. • Used in class 1,2,5 filling with conservative cavity preparation. • Avoid cavities in deciduous teeth.
AVAILABLE AS… • Powder – liquid system . • Pre – proportionate capsule . • Light cure system . • Dual cure system (chemical +light) .
POWDER acid soluble calcium fluoro aluminosilicate glass SiO2 -35-40% Al2O3 -20-25% AlF3 -1.5-3 % CaF2 -15-20 % NaF -4-10 % AlPO4 -1-15 %
Fluoride component - ceramic flux . • Lanthanum , strontium,barium , ZnO- radiopacity . • Fine colloidal Ag and amalgam - • enhance the properties.
LIQUID 40 -50% acidic solution…… Poly acrylic acid . Tartaric acid . Water.
Poly acrylic acid – very viscous • Tendancy to gelation . • Poly acrylic acid co-polymerized with itaconic acid maleic acid . • Increases the reactivity of liquid . • Decreases the viscosity . • Decreases the tendency to gelation .
TARTARIC ACID • Improve the handling character . • Decreases the viscosity . • Increases the working time . • Decreases the setting time . • WATER • Most important constituents . • Too much of water- weak cement . • Too little water – dehydration .
SETTING REACTION • The liquid acid may be freeze dried and combined with powder [ to have better shelf life and lower viscosity which are important characteristics for luting agents . • Mix can be done on a disposable moisture resistant paper pad or a glass slab . • A plastic spatula is preferred to a metal one to minimize contamination of the mix from eroded metal . • Large increment of powder are rapidly incorporated into the liquid and mixing should be completed within 40 sec Working time – short , not more than 3 min from start of mixing .
Powder and liquid mixed together Acid attacks the glass particles . Na,Ca,Al ,F ions are leached into the aquous solution Ca poly salts in the beginning and later Al – poly salts . Two salts cross links to form polyanionic chain.
STRUCTURE OF SET CEMENT Agglomerates of un reacted powder particles surrounded by silica gel and embedded in an amorphous matrix of hydrated Ca-Al polysalts . Fresh cement once hardened is prone to cracking and crazing due to loosely bound water which is readily removed from mix . Setting time – Type 1 4 – 5 min Type 2 7 min
Cavity preparation • Conditioning of tooth preparation • Proper manipulation • Protection of cement from setting • Finishing
CAVITY PREPARATION • Proper adhesion → resistance → retention is achieved by proper cavity preparation . • Eroded rough surfaces can be restored after acid etching alone without proper preparation.
CONDITIONING OF TOOTH PREPARATION • Chemical adhesion of cement with tooth surface . • Surface should be free of saliva, blood and completely dry . • Smear layer on the cavity should be removed . • This is done by • Pumice wash • 10 % polyacrylic acid • 37 % H3PO4 • Time 10 to 20 sec
Surface of dentin after application of………. • 37% ortho phosphoric acid • 10% poly acrylic acid
PROPER MANIPULATION • P/L ratio - type I 3:2 • type II 3:1 • Hand mixing • Capsule mixing
Hand mixing • Divide the dispersed powder into two equal parts . • Powder is incoperated rapidly into liquid . • Mixing should be done in a folding manner in order to preserve the gel structure . • 10 sec after adding first increment , 2nd increment is added to liquid . • The final mix should be with in 25 to 30 sec .
CAPSULE MIXING • Amalgamator is used for mixing • Powder and liquid contained within capsule by • removing the seal separating the liquid and powder . • After mixing is completed by vibration nozzle of the capsule is pierced and the cement is dispersed directly on the prepared cavity . • Advantage • Control over p/l ration • Convenience