Cavity preparation basic rules L. Roubalíková Preparation of dental caries (cavity preparation) Instrumental treatment that removes dental caries The rest of the tooth must be restorable with filling materials The rest of the tooth as well as the filling must be resistant against occlusal forces The risk of secondary caries must be minimized Basic rules Acces to the cavity Preparation of cavosurface margin and Extention for prevention Retention of the filling Resistance of the restored tooth Excavation of carious dentin Finishing of the walls Final control (light, mirir, magnification) Basic rules Acces to the cavity Preparation through the hard dental tissues Removal the undermined enamel Separation of teeth Separation or removal of gingiva Odstranění staré výplně Basic rules Preparation of cavity borders and extention for prevention (Cavosurface margin) Depends on Dental material Oral hygiene Precautions of secondary caries Basic rules Retention of the filling Precautions of its lost Macromechanical retention Micromechanical retention Chemical retention Basic rules Resistance of the restored tooth Against occlusal and other forces Depends on - Material - Individual occlusal forces Basic rules Excavation of carious dentin Necessary (risk of recurrent caries) Ball shaped (spheric) bur - slow speed (3000 rpm) or Excavator (hand instrument) Basic rules Finishing of the walls Depends on the kind of material - Bevel or without bevel - Fine diamond bur Basic rules Final control Direct or indirect view Good illumination Magnification Preparation • Hand Excavator, cleaver • Power driven Burs, diamonds Chisel – for enamel Cleaver Chisel for enamel Excavator Instruments for cavity preparation Power driven (powered) instruments for cutting - Rotary instruments Comon design characteristics lenka.roubalikova@tiscali.cz shank neck head Cutting instruments - burs Steel Tungsten carbide Cutting instruments – burs head shapes Round (ball shaped) Cutting instruments – burs head shapes Fissure with flat end Fissure with pointed end Straight or tapered form Cutting instruments – burs head shapes Pear Cutting instruments – burs head shapes Inverted conus Cutting instruments – diamonds Extra coarse – black Coarse – green Standard – blue or without any marker Fine - red Extra fine - yellow Ultrafine - white Cutting instruments – diamonds head shape • Ball, pear, cylinder,taper,flame, torpedo, lens and others….. Hazards with cutting instruments Pulpal precautions Soft tissue precautions Eye precautions Ear precautions Inhalation precautions Filling materials • Temporary • Definitive, permanent Temporary filling materials • Zinkoxidsulphate cement and one component derivates • Ziknoxidphosphate cement • Zinkoxideugenol cement • Polymer based materials • Guttapercha Permanent filling materials Amalgam Composites Glasionomers Amalgam L. Roubalíková Amalgam Metal-like restorative material composed of silver-tin-copper alloy and mercury. Types of amalgam restorative materials Low – Copper Amalgam (5% or less copper) Composition – wt% Silver 63 - 70 % Tin 26 – 28 % Copper 2 - 5% Zinc 0 - 2% Types of amalgam restorative materials High – Copper Amalgam (13% - 30%) copper Composition – wt% Silver 40 - 70 % Tin 26 – 30 % Copper 2 - 30% Zinc 0 - 2% Particles of the alloy Irregulary shaped (filings - lathe cut) Microsphers Combination of the two. Particles shape High – Copper Amalgam Microsphers of the same composition (unicompositional) Mixture of irregular and spherical particles of different or the same composition (admixed) Production of irregular particles Metal ingrediences heated, protected from oxidation, melted and poured into a mold to form an ingot. Phases of the alloy: (intermetallic compounds) Ag3Sn - g Cu3Sn - e Cu6Sn5 - h Ag4Sn - b Production of irregular particles Ingot cooled slowly Ingot heated at 400°C (6 – 8 hours) (homogeneous distribution of Ag3Sn) Ingot cut on the lathe, particles passed trough a fine sieve and ball milled to form the proper particle size. Aging of particles (60 - 100°C, 6 – 8 hours) Particle size: 60 – 120 mm in length 10 – 70 mm in width 10 – 35 mm in thickness Production of irregular particles Molten alloy is spraying into water under high pressue Irregulary shaped highcopper particles Production of spherical particles Molten alloy is spraying under high pressue of inert gas through a fine crack in a crucible into a large chamber Diameter of the spheres: 2 – 43mm Amalgamation processes Metal alloy is mixed with pure mercury Trituration Amalgamation processes Hg Sn Sn Sn Sn Sn Ag Ag Ag Ag Ag Cu Cu Cu Cu Cu Ag3Sn – g Cu3Sn – e Setting of low copper amalgam Principle of setting is crystallization Structure of the amalgam filling Ag-Hg: gamma 1 Sn-Hg: gamma 2 Gamma phase (Ag-Sn) does not dissolve completely These phases crystallized Risks of the gamma 2 phase • Non stable • Tin is released due to electrogalvanism in oral cavity and mercury from this phase reacts with remaining gamma phase. • This is external electrochemical corrosion. Low copper amalgam has worse mechanical and corrosion resistance than high copper amalgam High copper amalgam • Content of copper increased: 12 – 13% • (less tin) • Or up to 25% ( Less tin and silver) Better mechanical and corrosion resistance Amalgamation processes Sn Sn Sn Sn Sn Ag Ag Ag Ag Ag Cu Cu Cu Cu Cu Ag3Sn – g Cu3Sn – e Cu6Sn5 - h Sn7Hg – g2 Ag2Hg3 – g1 High copper amalgam g2 phase disappears or does not occur depending on the content of copper Amalgamation processes Sn Sn Sn Sn Sn Ag Ag Ag Ag Ag Cu Cu Cu Cu Cu Ag3Sn – g Cu3Sn – e Cu6Sn5 - h Sn7Hg – g2 Ag2Hg3 – g1 High copper amalgam – copper dissolved in mercury has high reaction afinity to tin that is also dissolved in mercury. It reacts with tin in gamma2 phase and eta phase comes into existence. The gamma 2 phase disappears. Amalgam - properties Amalgam Wear and pressure resistance (2mm thickness ast least)- brittleness Easy handling Low price Thermal and electrical conductivity Corrosion Bad aesthetics Creep Flow Biocompatibility • More than 160 years, more than 200 milions Ag fillings every year in USA. • Allergy rare • Precautions in children and in pregnancy. AMALGAM IS STILL A MATERIAL OF CHOICE Toxicity Organic compounds Vapours, aerosol Precautions • Ventilation • Rests of amalgam in water • Amalgam separators • Dangerous waste (180 110) Indications and contraindications of amalgam Indications • Moderate and large cavities in posterior area (class I., II. V) Contraindications Fillings in frontal area Pregnancy, children till the age of 6 Allergy Mixing of amalgam  Hand mixing (obsolete) Power driven trituration Amalgamators Cup Amalgam gun Condensor Amalgam gun Crucible (cup) Power driven condensation handpiece condensor Instruments Preparation instruments Filling instruments Carvers Burnishers Instruments Preparation instruments - power driven Burs Diamonds Instruments Preparation instruments - hand Chisel Excavator Amalgam carrier Amalgam carrier Instruments Filling instruments condensors and spatulas Condensor with flat front Condensor with flat front Condensor and burnisher - spatula combined Power driven condensor Special handpiece Burnisher - spatula Angular- trough edge trough face Burnisher – spatula, angular three face Instruments Burnishers Ball condensor – used as a burnisher at most