Cavity preparation basic rules L. Roubalfkova 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 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 shank neck head lenka.roubalikova@tiscali.cz 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 Straightjortapered 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 Tin Copper Zinc 40 - 70 % 26 - 30 % 2 - 30% 0 - 2% Particles of the alloy SIrregulary shaped (filings - lathe cut) S Microsphers SCombination 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: AgaSn - y Cu3Sn - s Cu6Sn5 - n Ag4Sn - p Production of irregular particles 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 jum in length 10 - 70 jum in width 10 - 35 jum in thickness Production of irregular particles Molten alloy is spraying into water under high pressue Irregulary shaped high-copper 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 - 43jum Amalgamation processes alloy is mixed with pure mercury Trituration Amalgamation processes Amalgamation processes Amalgamation processes Amalgam - properties Amalgam >Wear and pressure resistance (2mm thickness ast least) > Easy handling >Thermal and electrical conductivity > Corrosion > Bad aesthetics Trituration > Hand mixing (obsolete) > Power driven trituration Amalgamators Instruments > Preparation instruments > Filling instruments > Carvers > Burnishers Instruments Preparation instruments - power Instruments > Preparation instruments - hand Chisel J^^B Excavator Amalgam carrier Amalgam carrier Instruments > Filling instruments condensors and spatulas r. Condensor -stamen Condensor -stamen 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