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