Dental Instruments and Cutting mechanism Department of Operative Dentistry Universiti Kebangsaan Malaysia
Introduction • Instruments - tools used to examine, clean, cut and restore teeth. • Designed to allow to operator to do the treatment efficiently. • Two main types of cutting instruments: 1. Hand-held 2. Rotary
Hand Instruments • Uses include : – – – –
Examining mouth and teeth Scaling Cutting teeth and removing caries Placing, condensing, carving and shaping restorations – miscellaneous
Examination Instruments
Examination instruments Include : • Mirrors • Probes • Tweezers
Mirrors • Two types - rear surface and front surface mirrors. • Rear surface - has glass to protect the reflective layer, therefore less likely to get damaged. Disadvantage - double reflection from the glass and the silver especially when looking into deep cavities.
Mirrors
Front surface - clear image. Disadvantage - easily scratched
Probes • Straight and curved probe - probe no 9 and Briault • Used to examine teeth for caries, checking the margins of restorations and for examining the internal surface of cavities to check for remaining caries. • Periodontal probe (14W) - to measure periodontal pocket. Can be used to measure the depth of cavity
Probe • Briault probe - useful to check for proximal caries and caries at the EDJ.
Periodontal probe • Periodontal probe - blunt ended and graduated. It is used in measuring periodontal pocket and useful to measure the width of a tooth.
Tweezers • Used to carry and place cotton roll and pellets for drying or isolating teeth
Cutting Instruments
Types • • • • •
Chisels Hoe Hatchet Gingival marginal trimmer Excavators
Part of Hand Instruments • Comprise of the handle, shank and blade
Chisels • Curved or straight • Used for planing and cleaving unsupported enamel • Normally used with push motion
Hoe • Chisel with the angle approaching the right angle • Used in a pull motion
Hatchet • Chisel bladed instrument with the cutting edge in the plane of the shaft. • These instruments have a left and right blade and used for planing and cleaving unsupported enamel.
Gingival marginal trimmer • Modified hatchet has a cutting edge at an angle other than a right angle. • It comes in right and left as well as distal and mesial. • The primary use is to plane or bevel the cervical cavosurface margins.
Excavators • Ovoid or discoid in shape. • Should be kept sharp • Used for removing caries and softened dentine. • May be used for placing linings and carving restorations.
Instruments for Placing, Condensing and Shaping Restorations
Plastics
• Have flat blades or rounded ends. • Made of stainless steel • Those used for placing composite materials are often teflon coated or have titanium nitride ends.
Amalgam Carrier
Condensers or Pluggers • Used for compressing and forming materials particularly amalgam. • Used with heavy pressure • Available in various shape and size
Carvers • Have sharp blades and are used to carve materials by cutting or scraping. • They should be kept smooth and sharp.
Cleoid Discoid Carver
Maintaining Hand Instruments • Instruments should be kept sharp. • Use a flat sharpening stone to sharpen it and oil as lubricant.
Sterilisations of Hand Instruments • Most instruments are made from stainless steel. • Should be autoclaved after use in patient.
Rotary Instruments
Rotary Instruments Include : • Small burs, stone and discs which are held in a handpiece. The instrument is rotated in a handpiece by external power which may be from an electric motor or from compressed air.
Handpieces High speed : • Called an air rotor which gives the highest speeds ranging from 250, 000 to 500, 000 rpm. • Source of power is from the compressed air which drives a rotor or turbine which is mounted in the head of the handpiece.
High speed Handpieces • The bur is retained by friction, directly into the rotor of the handpiece and therefore revolves it. • Handpiece has built-in water spray to cool the tooth. • Operates in forward direction only
Handpieces Low speed : • Can either be straight or contra-angled • Contra-angled is used mainly inside the mouth. • Straight is used outside the mouth for trimming temporary crowns or dentures. • Speeds vary from 4, 000 to 40, 000 rpm. • Reduction handpiece can reduce speed to 550 rpm. • Can be used for finishing cavity margins and restoration
Slow-speed Handpiece • The drive is from an electric motor attached directly to the handpiece • Has a forward and a reverse control • Always check that handpiece is rotating in the correct direction ie anti clockwise as you look at it; clockwise as it enters the cavity.
How do we hold the handpiece ? • Pen grip • Palm grip • Finger grip Remember to protect the patient from injury. This can be done by stabilising the instrument by using a finger or thumb support on adjacent firm structures.
Air Turbine Handpiece • Noisy ! Danger to hearing. • Produce aerosol which can disseminate throughout the room • Spread of bacteria during the use of handpiece • Contamination into the mouth and eye
Contents of Aerosol • Particles of enamel and dentine (including caries) • Particles of restorative materials including amalgam and composite • Calculus • Lubricant oils • Fungi, bacteria, viruses • Possibly blood • water
Aerosol • Please protect yourself by wearing mask and protective glasses
Burs and Stones • Used for cutting, grinding and polishing • They are retained in the handpiece by 3 methods : – Friction grip in air turbine – Lacth grip in slow speed contra-angle h/p – A quick release chuck in the straight h/p
Burs - ISO Numbering System
Diamond Grit Sizes
Air turbine burs • Friction grip (FG) type • Have either diamond or tungsten carbide cutting ends
Low speed burs • Available with diamond, tungsten carbide and steel cutting ends • Comes in variety of shapes • Round burs are used to remove caries under low pressure
Efficient use of bur • Use as few burs as possible • Use the most efficient shape, size, surface, speed and technique
Stones • Usually used in the final stages of restoration • White stone • Green stone
Other finishing burs • Steel finishing burs for amalgam • Multifluted tungsten carbide burs for composite restorations • Various grades of diamonds • White, green and brown abrasive rubber points • Softlex discs
FG burs available in Simulasi Shape, made
Size
Type
Uses
Pear -short, TC
010, 012
Cutting
Access to caries
Pear - long, TC
012
Cutting
Preparation of the proximal box
Round, Dia
012, 014
Cutting
Access to caries in the anterior teeth
Transmetal, TC
012
Cutting
Remove amalgam
Micro-opener
007
Cutting
Widen fissure
Pointed - short, Dia
010
Polishing
Composite and GIC
Pointed - long, dia 010
Polishing
Composite and GIC
Egg shaped, TC
023
Polishing
Composite and GIC
End non-cutting
010
Cutting
Endo access cavity
SP burs available in Simulasi Shape, made
Size
Type
Uses
Pear -long, TC
012
Finishing
Finishing the cavity
Round, TC
008, 010, 012, 014, 016, 018,021
Cutting
Caries removal
White stone
023
Polishing
GIC and Composite
Green stone
023
Polishing
Amalgam
Brownie
Polishing
Amalgam
Greenie
Polishing
Amalgam
Mandrel
Polishing
Thank you