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 cavity borders and extention for prevention Retention of the filling Resistance of the restored tooth Excavation of carious dentin Finishing of the walls Final control Basic rules Acces to the cavity Preparation through the hard dental tissues Removing of the undermined enamel Separation of teeth Separation or removing of gingiva 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 Micromchanical 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 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: Ag3Sn - γ Cu3Sn - ε Cu6Sn5 - η Ag4Sn - β 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 μm in length 10 – 70 μm in width 10 – 35 μm 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 – 43μm 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 – γ Cu3Sn – ε Amalgamation processes Sn Sn Sn Sn Sn Ag Ag Ag Ag Ag Cu Cu Cu Cu Cu Ag3Sn – γ Cu3Sn – ε Cu6Sn5 - η Sn7Hg – γ2 Ag2Hg3 – γ1 Low copper amalgam Amalgamation processes Sn Sn Sn Sn Sn Ag Ag Ag Ag Ag Cu Cu Cu Cu Cu Ag3Sn – γ Cu3Sn – ε Cu6Sn5 - η Sn7Hg – γ2 Ag2Hg3 – γ1 High copper amalgam γ2 phase disappears or does not occur depending on the content of copper Amalgam - properties Amalgam Wear and pressure resistance (2mm thickness ast least) Easy handling Thermal and electrical conductivity Corrosion Bad aesthetics Flow Creep Conventional amalgam High silver amalgam • Ag 68 - 70% • Sn 24 – 26% • Cu -6% • (Zn -2%) Non gamma2 High copper amalgam • Copper 12 – 13% • Coppe 25% Better mechanical properties Low risk of corrosion Low flow and creep Mixing of amalgam Hand mixing (obsolete) Power driven trituration Amalgamators Instruments Preparation instruments Filling instruments Carvers Burnishers Instruments Preparation instruments - power driven Burs Diamonds Instruments Preparation instruments - hand Chisel Excavator Amalgam gun Crucible Amalgam carrier Amalgam carrier Instruments Filling instruments condensors and spatulas Condensor - stamen Condensor with straight front Condensor and burnisher - spatula combined Power driven condensor - stamen Special handpiece Burnisher - spatula Angular- trough edge trough face Burnisher – spatula, angular three face Instruments Burnishers Ball condensor – used as a burnisher at most